Skip to main content
Full access
New Research
Published Online: 1 September 2011

A Randomized Trial Examining the Effectiveness of Switching From Olanzapine, Quetiapine, or Risperidone to Aripiprazole to Reduce Metabolic Risk: Comparison of Antipsychotics for Metabolic Problems (CAMP)

Abstract

Patients with a BMI of 27 or higher and a non-HDL cholesterol level of 130 mg/dl or higher on stable doses of olanzapine, quetiapine, or risperidone were randomly assigned to stay on their current medication or switch to aripiprazole for 24 weeks. Patients switched to aripiprazole saw greater decreases in cholesterol levels, larger reductions in weight, and a net reduction of serum triglycerides. There was no difference in the rate of treatment failure, but nearly twice as many patients discontinued the new aripiprazole regimen before 24 weeks.

Abstract

Objective:

The authors conducted a multisite randomized controlled trial examining the strategy of switching from olanzapine, quetiapine, or risperidone to aripiprazole to ameliorate metabolic risk factors for cardiovascular disease.

Method:

Patients with schizophrenia or schizoaffective disorder with a body mass index ≥27 and non-high-density lipoprotein (non-HDL) cholesterol ≥130 mg/dl who were on a stable treatment dosage of olanzapine, quetiapine, or risperidone were randomly assigned to switch to ari-piprazole (N=109) for 24 weeks or stay on their current medication (N=106). All participants were enrolled in a behaviorally oriented diet and exercise program. Clinical raters were blinded to treatment assignment. The primary and key secondary outcomes were change in non-HDL cholesterol and efficacy failure, respectively.

Results:

The prespecified primary analysis included 89 switchers and 98 stayers who had at least one postbaseline non-HDL cholesterol measurement. The least squares mean estimates of non-HDL cholesterol decreased more for the switch group than for the stay group (–20.2 mg/dl and –10.8 mg/dl, respectively). Switching was associated with larger weight reductions (least squares mean=2.9 kg) and a net reduction of serum triglycerides of 32.7 mg/dl. Twenty-two switchers (20.6%) and 18 stayers (17.0%) experienced protocol-defined efficacy failure. Forty-seven switchers (43.9%) and 26 stayers (24.5%) discontinued the assigned antipsychotic medication before 24 weeks.

Conclusions:

Switching to aripiprazole led to improvement of non-HDL cholesterol levels and other metabolic parameters. Rates of efficacy failure were similar between groups, but switching to aripiprazole was associated with a higher rate of treatment discontinuation. In the context of close clinical monitoring, switching from an antipsychotic with high metabolic risk to one with lower risk to improve metabolic parameters is an effective strategy.
Some commonly used antipsychotic medications (e.g., olanzapine, quetiapine, and risperidone) are associated with higher rates of metabolic abnormalities that predispose patients to cardiovascular disease (17). Individuals with severe mental disorders have a substantially shortened life expectancy, and cardiovascular diseases are among the leading causes of premature mortality in this group (8). Thus, appropriate treatment strategies for patients who take antipsychotics and also have significant risk factors for cardiovascular disease are needed. Among the methods for managing this risk in patients treated with antipsychotic drugs, a commonly chosen option of uncertain effectiveness is switching from drugs with a high liability for producing metabolic side effects to one with a low liability. This is of particular interest for individuals with schizophrenia or schizoaffective disorder who are clinically stable taking an antipsychotic medication that has a relatively high risk of metabolic side effects. The possible benefits of switching to a drug associated with fewer adverse metabolic effects must be weighed against the potential risk of clinical instability associated with changing treatment.
There are numerous modifiable risk factors for cardiovascular disease, including obesity, dyslipidemia, hypertension, and impaired glucose metabolism (including insulin resistance and diabetes mellitus). Recent attention has focused on non-high-density lipoprotein (non-HDL) cholesterol, which contains all known and potentially atherogenic lipid particles and has been shown in large cohort studies to be strongly associated with cardiovascular morbidity and mortality.
For example, the Lipid Research Clinics Program Follow-Up Study, which followed a cohort of 2,462 middle-aged men and women for an average of 19 years, found that non-HDL cholesterol levels at study entry strongly predicted cardiovascular disease mortality (9). Differences of 30 mg/dl in non-HDL cholesterol at baseline were associated with a 19% increase in cardiovascular disease mortality in men and an 11% increase in women. In the Bypass Angioplasty Revascularization Investigation (BARI), in which 1,514 patients with multivessel coronary artery disease were followed for 5 years, non-HDL cholesterol was strongly and independently associated with nonfatal myocardial infarction and angina pectoris; increments of 10 mg/dl in non-HDL cholesterol were associated with a 5% increased risk of nonfatal myocardial infarction and a 10% increased risk of angina pectoris (10).
In this article, we report the primary and key secondary efficacy and safety results of a 24-week randomized controlled clinical trial. The study examined the effectiveness of switching treatment for patients with schizophrenia or schizoaffective disorder from olanzapine, quetiapine, or risperidone to treatment with aripiprazole as a strategy to reduce metabolic problems associated with antipsychotic medications. We considered studying the switch to other antipsychotics with favorable metabolic profiles, including ziprasidone and molindone (3, 6, 1113), but chose aripiprazole because it was the newest option and we expected it would be of most clinical interest when the study was completed.
We hypothesized that switching to aripiprazole would result in an improvement in metabolic measures compared to staying on the current antipsychotic medication. We also wanted to determine if any metabolic benefits of switching to aripiprazole would be accompanied by clinical destabilization after switching from an antipsychotic that was working well. The primary efficacy outcome was the difference in non-HDL cholesterol from baseline between the two treatment groups. The key secondary outcome was efficacy failure, defined in the protocol as psychiatric hospitalization, a 25% increase in the total Positive and Negative Syndrome Scale (PANSS; 14) score, or ratings of much worse or very much worse on the Clinical Global Impressions (CGI) change subscale (15).

Method

Participants

The Comparison of Antipsychotics for Metabolic Problems (CAMP) was a multisite, parallel-group, randomized controlled clinical trial. Participants were individuals with schizophrenia or schizoaffective disorder who had achieved clinical stability with olanzapine, quetiapine, or risperidone and who were at increased risk for cardiovascular disease as indicated by a body mass index (BMI) ≥27 and a non-HDL cholesterol ≥130 mg/dl (if non-HDL cholesterol was 130–139 mg/dL, then low-density lipoprotein [LDL] cholesterol was required to be ≥100 mg/dl). The patients were required to be on the qualifying drug for a minimum of 3 months without dosage adjustments and without any other antipsychotic for 1 month prior to enrollment. The patients entered the study in order to improve their metabolic risk profile. All participants provided written informed consent after the study procedures had been fully explained. The study was conducted at 27 clinical research centers affiliated with the Schizophrenia Trials Network in the United States.
The patients were randomly assigned on a 1:1 basis to either switch to aripiprazole or stay on their current antipsychotic medication. Treatment assignments (stay versus switch) were stratified by the antipsychotic medication taken when entering the study (olanzapine, quetiapine, or risperidone) and were centrally implemented via a web-based system accessed by the clinical centers. Individuals assigned to stay on their current antipsychotic remained on their prestudy dosage with adjustments only as clinically indicated. The allowed dosages were as follows: olanzapine, 5–20 mg/day; quetiapine, 200–1,200 mg/day; and risperidone, 1–16 mg/day. Patients assigned to switch to aripiprazole began taking aripiprazole, 5 mg/day, and continued their previous antipsychotic medication and dose for 1 week. After 1 week, the aripiprazole dosage was increased to 10 mg/day and the previous drug's dosage was reduced 25%–50%. After 2 weeks, the aripiprazole dosage could be increased to 15 mg/day while the previous drug's dosage was reduced 50%–75% from the original dosage. After 3 weeks, the available range for aripiprazole was 5–20 mg/day and the previous drug was stopped. After 4 weeks, the allowed dosage range for aripiprazole was 5–30 mg/day.
All participants received a manualized behavioral intervention, adapted from a group treatment (16, 17), that was aimed at improving exercise and diet habits to reduce the risk of cardiovascular disease. Patients returned to the clinic for weekly visits during the first month of the treatment period and every 4 weeks after that, and laboratory assessments were conducted every 4 weeks. The behavioral intervention was provided in person at all postbaseline study visits. After the first 4 weeks, study personnel made a telephone call to reinforce the behavioral treatment lessons between each of the monthly visits.
The raters of symptoms (PANSS), global clinical status (CGI), and extrapyramidal side effects (the Abnormal Involuntary Movement Scale [18], the Barnes Akathisia Scale [19], and the Simpson-Angus Extrapyramidal Symptoms Scale [20]) were blinded to treatment assignment. Participants and their physicians were aware of their medication assignments.
The addition of lithium, valproate, lipid-lowering agents such as statins, or drugs prescribed for weight loss was not allowed during the trial because of possible effects on the primary study outcome. Individuals taking stable doses of lithium, valproate, or lipid-lowering medications at the time of study entry could continue these treatments, but dose adjustments during the treatment period were not allowed. All other medications, except for nonstudy antipsychotics, were allowed.

Statistical Methods

The primary efficacy analysis was conducted on the efficacy-evaluable population, defined as all patients randomly assigned to a study group who received at least one dose of study medication and completed at least one postbaseline efficacy assessment. The efficacy analysis corresponded to a comparison of change in non-HDL cholesterol from baseline to 24 weeks between treatment groups (stay versus switch). Repeated measurements mixed effects linear models were fit for the primary analysis and secondary analyses of continuous outcomes that appropriately accounted for the correlation among repeated clinical assessments and randomly missing data (21). Models included fixed effects for stratification (incoming medication), pooled clinical site, baseline value, treatment, time (weeks in study), and time by treatment interactions. An unstructured variance-covariance matrix was assumed, and least squares means at 24 weeks were the a priori basis for the treatment comparisons. Outcome measurements obtained following a prohibited change in dose or initiation of a disallowed medication were excluded from all efficacy analyses, as specified a priori in the study protocol. The primary efficacy analysis was repeated using all available measurements to assess the sensitivity of results.
Secondary analyses of efficacy failure and treatment discontinuation were based on the intent-to-treat population, defined as all patients randomly assigned to a study group who received at least one dose of study medication. We used Cochran-Mantel-Haenszel tests stratified by incoming medication to compare treatment groups with respect to the proportion experiencing efficacy failure and the proportion discontinuing treatment. Kaplan-Meier curves for time to efficacy failure and time to treatment discontinuation were generated, and treatment groups were compared using log-rank tests. Cox proportional hazards models were additionally fit to compare time to event outcomes, controlling for incoming medication and pooled clinical site.

Results

The study was conducted between January 2007 and March 2010. Figure 1 summarizes the progress of patients who were screened and randomly assigned to each group. Of the 215 patients who met inclusion criteria, 109 were switched to aripiprazole and 106 remained on their current antipsychotic. Baseline demographic and clinical characteristics of all participants are summarized in Table 1.
FIGURE 1. Participant Enrollment and Follow-Up in a Study Comparing Antipsychotics for Metabolic Problems
TABLE 1. Baseline Demographic and Clinical Characteristics of Participants in a Study Comparing Antipsychotics for Metabolic Problemsa
 Total (N=215)Switch Group (N=109)bStay Group (N=106)b
CharacteristicsMeanSDMeanSDMeanSD
Age (years)4111.14011.74210.5
Education (years)122.5122.3132.6
Non-HDL cholesterol (mg/dL)17332.816931.917633.5
HDL cholesterol (mg/dL)4411.44512.44310.2
Weight (kg)10320.710420.810220.6
Body mass index356.5356.3356.6
Total cholesterol (mg/dL)21733.321433.522033.0
LDL cholesterol (mg/dL)14028.013825.614230.3
Triglycerides (mg/dL)16994.116288.817599.3
Triglycerides/HDL ratio43.143.053.2
Hemoglobin A1c (%)60.460.460.4
Fasting glucose (mg/dL)9611.49610.89712.1
2-hour glucose (mg/dL)12741.112637.912744.4
Fasting insulin (mU/L)1613.11610.71715.3
2-hour insulin (mU/L)87103.692110.78296.1
C-reactive protein (mg/dL)78.578.678.5
PANSS total score6616.36516.06716.6
CGI severity score40.940.940.9
SF-12 mental health score4511.54411.44611.4
SF-12 physical health score4510.3469.94510.6
IWQoL total score6628.86528.86629.0
 N%N%N%
Sex 
    Male13763.76862.46965.1
    Female7836.34137.63734.9
Race 
    White12357.26559.65854.7
    Black8037.23935.84138.7
    Other104.743.765.7
Spanish, Hispanic, or Latino ethnicity3918.11917.42018.9
High school education or above16677.28376.18378.3
Marital status 
    Married167.498.376.6
    Previously married6630.73330.33331.1
    Never married13361.96761.56662.3
Living situation 
    Independent/nonstructured17782.39082.68782.1
    Other3817.71917.41917.9
a
HDL=high-density lipoprotein; LDL=low-density lipoprotein; PANSS=Positive and Negative Syndrome Scale; CGI=Clinical Global Impressions Scale; SF-12=Medical Outcomes Study 12-Item Short-Form Health Survey; IWQoL=Impact of Weight on Quality of Life.
b
Participants in the switch group were assigned to treatment with aripiprazole. Participants in the stay group remained on olanzapine, quetiapine, or risperidone.
Two patients who were assigned to switch medications never took the study drug and were therefore not included in the intent-to-treat population. Eighteen of those in the switch group (16.8%) compared with eight in the stay group (7.5%) stopped the protocol-specified treatment in the first 4 weeks before completing the time allowed for cross-titration to aripiprazole and before the first follow-up laboratory tests were conducted, and they were therefore excluded from the efficacy-evaluable population. Of these, 17 of those who switched (15.9%) and six of those who stayed (5.6%) discontinued the assigned antipsychotic, and the remaining three (one switcher and two stayers) took disallowed medications in the first month. The primary outcome and other metabolic parameters were evaluated in 89 switchers and 98 stayers who completed at least 1 month of study participation and thus had at least one postbaseline measurement of the primary outcome on the assigned treatment.
At study entry, the mean daily doses of the qualifying medications were 18.5 mg of olanzapine, 502 mg of quetiapine, and 4.1 mg of risperidone. Mean daily doses for patients during the study were 16.9 mg of aripiprazole, 18.0 mg of olanzapine, 572.0 mg of quetiapine, and 4.1 mg of risperidone.

Metabolic Outcomes

For the primary outcome (change in non-HDL cholesterol) the least squares means decreased more for the switch than the stay groups (–20.2 mg/dl compared with –10.8 mg/dl), with a difference of –9.4 mg/dl (95% confidence interval [95% CI]=–2.2 to –16.5, p=0.010). Switchers lost more weight than stayers (–3.6 kg compared with –0.7 kg) with a difference of –2.9 kg (95% CI=–1.6 to –4.2, p<0.001) and had a larger BMI reduction of –1.07 units (p<0.001). Triglycerides decreased for the switch group and increased for the stay group (–25.7 mg/dl compared with +7.0 mg/dl), yielding a difference of –32.7 mg/dl (95% CI=–12.1 to –53.4, p=0.002). As seen in Table 2, there were no significant differences between the treatment groups in changes in HDL or LDL cholesterol. There was a trend favoring switching compared with staying in reducing the inflammatory marker C-reactive protein. Figure 2 and Figure 3 demonstrate the time course of changes in non-HDL cholesterol, triglycerides, and weight. The benefit of switching for non-HDL cholesterol and triglycerides was almost completely realized after only 1 month, while the advantage of switching for weight change accrued over the 24 weeks of the study. In our models, time and time-by-treatment parameters were significant for weight change but not for non-HDL cholesterol or triglycerides. Mean weight change per month on study treatment was –0.8 kg (SD=1.4 kg) for switchers and –0.1 kg (SD=1.0 kg) for stayers.
TABLE 2. Outcome Measures of Effectiveness in the Efficacy-Evaluable Population by Treatment Group in a Study Comparing Antipsychotics for Metabolic Problemsa
 Switch Group (N=89)bStay Group (N=98)bAnalysis
Outcome ChangesMeanSEMeanSEDifference95% CIpc
Primary outcome change 
    Non-HDL cholesterol (mg/dL)–20.22.87–10.82.579.42.2, 16.50.0102
Secondary outcome changes 
    Metabolic 
        HDL cholesterol (mg/dL)0.60.76–0.10.68–0.7–2.7, 1.30.4693
        Weight (kg)–3.60.48–0.70.442.91.6, 4.2<0.0001
        Body mass index–1.30.17–0.20.151.10.6, 1.5<0.0001
        Total cholesterol (mg/dL)–19.62.99–10.82.698.81.5, 16.10.0179
        LDL cholesterol (mg/dL)–15.42.76–12.52.542.9–3.9, 9.60.4003
        Triglycerides–25.78.107.07.2032.712.1, 53.40.0020
        Triglycerides/HDL ratio–0.80.250.20.221.00.3, 1.60.0029
        Hemoglobin A1c (%)0.00.030.10.030.0–0.1, 0.10.6413
        Fasting glucose (mg/dL)0.51.434.01.253.5–0.2, 7.10.0607
        Fasting insulin (mU/L)1.02.586.72.265.7–1.0, 12.40.0963
        2-hour glucose (mg/dL)–10.34.19–6.13.754.3–5.7, 14.30.4012
        2-hour insulin (mU/L)–31.17.72–6.86.8324.24.8, 43.60.0144
        C-reactive protein (mg/dL)–1.71.281.51.153.2–0.1, 6.50.0557
    Measures of clinical status 
        PANSS total score–5.01.45–3.91.311.1–2.3, 4.60.5180
        CGI severity subscale score–0.20.09–0.20.09–0.0–0.2, 0.20.8566
        SF-12 mental health score0.31.370.31.13–0.1–3.6, 3.40.9680d
        SF-12 physical health score2.11.09–1.60.91–3.7–6.5, –0.90.0105d
        IWQoL total score–14.22.57–4.72.229.63.3, 15.80.0028d
a
Least squares means and standard errors from the mixed model are presented. HDL=high-density lipoprotein; LDL=low-density lipoprotein; PANSS=Positive and Negative Syndrome Scale; CGI=Clinical Global Impressions Scale; SF-12=Medical Outcomes Study 12-Item Short-Form Health Survey; IWQoL=Impact of Weight on Quality of Life.
b
Participants in the switch group were assigned to treatment with aripiprazole. Participants in the stay group remained on olanzapine, quetiapine, or risperidone.
c
The p value is for the comparison of least squares means in change from baseline between stay and switch at the 24-week visit. A linear mixed model that appropriately accounts for correlations among clinic visits associated with a single patient and for randomly missing data is used to test for a difference in least squares means. Model effects include main effects corresponding to incoming medication, baseline, visits, and treatments, as well as a treatment-by-visit interaction term. Pooled clinical center is a random effect.
d
The p values for the comparison of these outcomes, which are measured at the last follow-up only, are from a mixed model with fixed effects incoming study medication, baseline and treatment, and random effect pooled site.
FIGURE 2. Time Course of Changes in Non-HDL Cholesterol, Triglycerides, and Weight Values for the Efficacy-Evaluable Population (N=187)a
a Least squares means from the mixed model. Change from baseline was the outcome variable. Treatment, week, baseline value, incoming medication, and treatment-by-week interaction were covariates in the mixed model.
*p=0.0102.
**p=0.0020.
***p<0.0001.
FIGURE 3. Kaplan-Meier Survival Curves for the Intent-To-Treat Population (N=215) in a Study Comparing Antipsychotics for Metabolic Problemsa
a Log-rank test p=0.2993 for time to efficacy failure in days and p=0.0021 for time to all-cause treatment discontinuation in days.
On measures of glucose metabolism and insulin sensitivity, there was no difference between switchers and stayers in fasting glucose, fasting insulin, or glycosolated hemoglobin. There was no difference in glucose levels 2 hours after oral ingestion of 75 mg of glucose, but the 2-hour insulin level decreased more for those assigned to switch compared with those assigned to stay (–31.1 mg/dl and –6.8 mg/dl, respectively), with a difference of –24.2 mg/dl (p=0.014).

Measures of Clinical Status

Twenty-two patients assigned to switch to aripiprazole (20.6%) and 18 assigned to stay on the current antipsychotic (17.0%) experienced efficacy failure. There was no significant difference in time to efficacy failure (hazard ratio for switching=0.747; 95% CI=0.395–1.413, p=0.3703). There were no differences between groups in psychopathology changes as measured by the PANSS total score, change in CGI severity score, or change in the Medical Outcomes Study 12-Item Short-Form Health Survey (22) mental health scores. The 12-Item Short-Form Health Survey physical health score worsened slightly for the stayers and improved for the switchers, yielding an advantage for the switchers of 3.7 points (p=0.0105). On the Impact of Weight on Quality of Life–Lite Questionnaire, a validated measure of quality of life related to weight (23), switchers improved more than stayers (–14.2 compared with –4.7 points, p=0.0028).

Treatment Discontinuation

Eighteen of those assigned to switch to aripiprazole (16.8%) discontinued the protocol-specified treatment before 1 month had elapsed compared with eight of those assigned to stay on the current medication (7.5%). Overall, 51 switchers (47.7%) and 29 stayers (27.4%) stopped the protocol-specified treatment (by stopping the assigned antipsychotic or beginning a prohibited medication) before 24 weeks were complete (p=0.0019). Participants in the switch group discontinued the protocol-specified treatment (for any cause) earlier than those in the stay group (hazard ratio=0.456; 95% CI=0.285–0.728, p=0.0010). Forty-seven switchers (43.9%) and 26 stayers (24.5%) stopped taking the assigned antipsychotic altogether before 24 weeks were complete.

Adverse Effects

We systematically inquired about 20 adverse events commonly associated with antipsychotic medications. Table 3 lists the frequencies for participant ratings of each of these side effects as moderate or severe. Considering the adverse effects reported after baseline with differences of approximately 5% or more between the stay and switch groups, insomnia was more common in the switch group but there was more sleepiness, hypersomnia, nausea, dry mouth, increased appetite, and akinesia among the stay group. Among the switchers, 18 patients (16.8%) experienced a total of 21 serious adverse events (including medically significant or life-threatening events, hospitalizations, or extended hospitalizations), compared to 10 stayers (9.4%) who experienced 14 serious adverse events. One stayer and no switchers discontinued treatment due to akathisia/activation. Eight switchers (7.5%) and five stayers (4.7%) were hospitalized for psychiatric reasons. There were no deaths in the study.
TABLE 3. General Safety Summary of a Comparison of Antipsychotics for Metabolic Problemsa
 Total (N=213)Switch Group (N=107)bStay Group (N=106)b 
MeasureN%N%N%p
Reason for participant discontinuation 
    Procotol-specified efficacy failurec4018.82220.61817.00.4782
    Early discontinuation of protocol-specified treatmentd8037.65147.72927.40.0019
    Discontinuation of study antipsychotic due to any causee7334.34743.92624.5 
    Discontinuation of study antipsychotic due to inefficacyf219.91816.832.8 
    Discontinuation of study antipsychotic due to intolerabilityg136.176.565.7 
    Dropped out (no information available)2310.81514.087.5 
    Dropped out due to withdrawn consenth146.654.798.5 
    Discontinuation of study antipsychotic due to other reasonsi20.921.900.0 
Any serious adverse eventsj2813.11816.8109.4 
Any psychiatric hospitalization136.187.554.7 
Deaths00.000.000.0 
Any adverse events rated moderate or severe16075.18175.77974.5 
At least one adverse event rated moderate or severe by systematic inquiry15472.37772.07772.6 
    Insomnia7334.34441.12927.4 
    Sleepiness6229.12725.23533.0 
    Dry mouth6028.22422.43634.0 
    Akathisia/activation5525.82927.12624.5 
    Problems with sex drive5023.52422.42624.5 
    Increased appetite4420.71816.82624.5 
    Weight gain4119.22018.72119.8 
    Constipation4018.82018.72018.9 
    Akinesia3918.31413.12523.6 
    Problems with sexual orgasm3918.32018.71917.9 
    Problems with sexual arousal3817.82018.71817.0 
    Hypersomnia3717.41615.02119.8 
    Orthostatic faintness3717.41917.81817.0 
    Nausea3014.11211.21817.0 
    Incontinence/nocturia2210.398.41312.3 
    Skin rash209.487.51211.3 
    Menstrual irregularities167.5109.365.7 
    Sialorrhea157.087.576.6 
    Urinary hesitancy94.254.743.8 
    Gynecomastia/galactorrhea62.821.943.8 
a
Uses intent-to-treat population.
b
Participants in the switch group were assigned to treatment with aripiprazole. Participants in the stay group remained on olanzapine, quetiapine, or risperidone.
c
Participants who had either a psychiatric hospitalization, a 25% increase from baseline on the Positive and Negative Syndrome Scale (or a 10-point increase for individuals with a baseline total score of 40 or less), or substantial clinical deterioration on the Clinical Global Impressions change subscale (i.e., 6=much worse or 7=very much worse). The p value for the comparison of this binary outcome is from a Cochran-Mantel-Haenszel test stratified by incoming antipsychotic (olanzapine, quetiapine, or risperidone).
d
Includes both early treatment discontinuations AND participants who started/stopped/changed the dose of a disallowed medication (lipid-lowering agent or mood stabilizer). The p value for the comparison of this binary outcome is from a Cochran-Mantel-Haenszel test stratified by incoming antipsychotic (olanzapine, quetiapine, or risperidone).
e
Participants who did not complete 24 weeks on the assigned treatment.
f
Study treatment stopped because of positive symptoms, negative symptoms, mood symptoms, or other inefficacy/inadequate therapeutic effect.
g
Study treatment stopped because of weight, lipids, glucose, extrapyramidal side effects, tardive dyskinesia, akathisia/activation, sedation, insomnia, agitation, sexual side effects, nausea, or other unacceptable side effects.
h
Study treatment stopped because the patient did not see a need for treatment or the patient no longer wanted to participate in the study.
i
Study treatment stopped because of administrative reasons.
j
Only events after randomization are included here.

Sensitivity Analysis

A sensitivity analysis of the primary efficacy outcome (change in non-HDL cholesterol) was conducted using a modified intent-to-treat population of participants with at least one postbaseline non-HDL measurement. A repeated measurements mixed effects linear model was fit using all available measurements of non-HDL cholesterol, regardless of disallowed medication usage or early discontinuation of the prescribed antipsychotic, to predict the change at week 24. The change remained greater among patients switching to aripiprazole than those remaining on their original medication, but statistical significance was not achieved. The difference in least squares means was 5.8 mg/dl (p=0.104).

Discussion

The study was conducted at 27 U.S. research sites that were selected to include a demographically diverse population to enhance the generalizability of the results. Enrollment criteria were designed to include a wide spectrum of individuals who might consider switching medications because of metabolic problems, although those with minimal metabolic problems and those with severe metabolic problems that needed immediate intervention were excluded. Therefore, the results of this study might best be generalized to individuals with chronic schizophrenia or schizoaffective disorder with moderate metabolic problems for whom a medication change or a lifestyle intervention focused on diet and exercise is the appropriate first step.
In this study, switching from olanzapine, quetiapine, or risperidone to aripiprazole was effective in helping many patients improve the results of their lipid profiles (lower non-HDL cholesterol and triglycerides levels) and lose weight. The 9 mg/dl reduction in non-HDL cholesterol is slightly less than the 10 mg/dl difference that significantly reduced cardiovascular morbidity in the Bypass Angioplasty Revascularization Investigation study (10). The 1.1 unit reduction in BMI is above the 1 unit considered clinically significant by a panel of antipsychotic experts who created monitoring guidelines (24). Because weight loss continued at the end of the study, it is possible that our results underestimate the long-term benefit of switching on this secondary outcome. Because non-HDL cholesterol was the primary predesignated outcome, results pertaining to non-HDL cholesterol provide stronger evidence than those for secondary outcomes. These results are consistent with those in a randomized controlled trial reported by Newcomer and colleagues (25) that examined switching from olanzapine to aripiprazole over 16 weeks. In that study, switchers had a 3.21 kg advantage in weight loss after 16 weeks, a reduction in triglycerides (compared with an increase for the stayers), and a 15.6 mg/dl larger reduction in non-HDL cholesterol.
Aripiprazole is one of several antipsychotics, including ziprasidone and molindone, associated with a relatively low risk of metabolic problems. In studies, switching to ziprasidone has been associated with significant improvement in metabolic parameters (12, 13). In addition, other available strategies to address metabolic problems in patients taking antipsychotic medications include statins (HMG-CoA reductase inhibitors) to reduce LDL cholesterol and metformin to reduce weight. Statins tend to benefit LDL and triglycerides rather than HDL or weight. The different statins have variable effects on LDL cholesterol, but they are typically associated with reductions in LDL cholesterol of 30%–60% (26). Short-term studies of metformin have shown that it is effective and well tolerated in promoting weight loss among individuals who have recently gained weight while taking an antipsychotic (27), individuals experiencing a first episode of psychosis (28), and even individuals whose increased weight is not of recent onset (29).
Switching antipsychotics by beginning aripiprazole at a low dose and titrating upward while slowly discontinuing the previous antipsychotic over 1 month was not associated with a significant increase in efficacy failures as indicated by need for hospitalization, substantial worsening of symptoms, or global clinical status. However, a larger percentage of individuals assigned to switch to aripiprazole discontinued the assigned treatment over the 24 weeks of the study. In some cases, the medication discontinuation was attributed to inadequate efficacy by the study clinician but did not meet the study criteria for efficacy failure. The protocol was designed to minimize risks for participants and allowed study physicians to intervene to prevent problems before they became severe. For example, when clinical worsening was detected, study physicians could intervene by discontinuing the protocol-specified treatment, thus averting full-blown efficacy failure. We investigated this possibility by comparing the PANSS scores of participants who met the protocol's efficacy failure criteria to the PANSS scores of participants whose treatment discontinuations were judged to be a result of inadequate efficacy but who did not meet the efficacy failure criteria; the PANSS scores of those who met efficacy failure criteria were higher (mean=71.7 [SD=22.9]) than those who did not meet the criteria (mean=59.5 [SD=15.2]). This suggests that careful clinical monitoring following a medication switch, accompanied by appropriate clinical intervention when poor efficacy is detected (e.g., stopping the new antipsychotic and restarting the previous one), can reduce the risk of severe symptom exacerbations and the need for hospitalization.
Because the goal of the study was to evaluate the effect of switching antipsychotic medications on metabolic parameters, some common medication changes that were known to affect these parameters were not allowed. For those few patients who took the proscribed medications but continued the assigned antipsychotic, we used only those measurements taken before the disallowed change occurred in the primary analyses. Seven such deviations from protocol-specified treatment occurred; four were in the switch group and three in the stay group. In addition, some patients contributed data after they had stopped taking the assigned antipsychotic. Results from the sensitivity analyses that were conducted to assess the impact of these exclusions and early dropouts for other reasons showed that an advantage for switching remained, although statistical significance was not achieved.
Our study focused on the primary comparison of staying on current medication or switching. Secondary analyses examining the effects for each of the three allowed antipsychotics at study entry are provided in the data supplement that accompanies the online edition of this article. These secondary analyses provide only suggestive information about the impact of switching from these drugs.
Open-label treatment is a limitation of this study, particularly for outcomes not measured in the laboratory but instead subject to clinical judgment. For example, a belief that olanzapine has superior efficacy could have contributed to the early discontinuations among those who entered the study taking olanzapine but were assigned to switch to aripiprazole (supplemental Table 3). The excess of early treatment discontinuations in the olanzapine group suggests that switching from olanzapine was either more difficult than switching from the other drugs or, perhaps, resulted from an expectation bias that this change would be the most difficult.
In conclusion, switching from a medication associated with substantial risk of metabolic problems to one with a lower risk of these complications is a reasonable clinical option if careful cross-titration and close monitoring is possible. Careful clinical monitoring during and after a switch is necessary, and the diligence of clinicians is likely a principal reason that those who switched did not experience a higher rate of efficacy failures than those who stayed on their original antipsychotic. If switching medications is unsuccessful, other approaches to reduce some of the risk factors for cardiovascular disease are available, including adding metformin or a statin. The switch in medications was effective in the presence of a behavioral intervention that was focused on improving diet and exercise habits, which also benefitted the group that did not change medications.

Footnotes

Received Nov. 8, 2010; revisions received Feb. 17 and Apr. 12, 2011; accepted Apr. 29, 2011.
The study was conducted by the following investigators: Lawrence Adler, Glen Burnie, Md.; Farooq Amin, Atlanta; Michael Barber, Houston; Peter Buckley, Augusta, Ga.; Matthew Byerly, Dallas; Jose Canive, Albuquerque, N.Mex.; Stanley Caroff, Philadelphia; Cyril D'Souza, New Haven, Conn.; Ira Glick, Palo Alto, Calif.; Daniel Mamah, St. Louis; Don Goff, Boston; Anita Kablinger, Shreveport, La.; Ahsan Kahn, Wichita, Kan.; Steven Lamberti, Rochester, N.Y.; Jeffrey Lieberman, New York; Theo Manschreck, Fall River, Mass.; Joseph McEvoy, Butner, N.C.; Alec Miller, San Antonio, Tex.; Del Miller, Iowa City, Iowa; James Rosenthal, Colson, Calif.; Henry Nasrallah, Cincinnati; Stephen Olson, Minneapolis; Jayendra Patel, Worcester, Mass.; Bruce Saltz, Boca Raton, Fla.; Richard Steinbook, Miami; and Scott Stroup, Chapel Hill, N.C.

Supplementary Material

File (ajp_168_09_947_01.pdf)
File (ajp_168_09_947_02.pdf)
File (ajp_168_09_947_03.pdf)

References

1.
American Diabetes Association, American Psychiatric Association, American Association of Clinical Endocrinologists, North American Association for the Study of Obesity: Consensus development conference on antipsychotic drugs and obesity and diabetes. Diabetes Care 2004; 27:596–601
2.
Newcomer JW, Ratner RE, Eriksson JW, Emsley R, Meulien D, Miller F, Leonova-Edlund J, Leong RW, Brecher M: A 24-week, multicenter, open-label, randomized study to compare changes in glucose metabolism in patients with schizophrenia receiving treatment with olanzapine, quetiapine, or risperidone. J Clin Psychiatry 2009; 70:487–499
3.
Newcomer JW: Second-generation (atypical) antipsychotics and metabolic effects: a comprehensive literature review. CNS Drugs 2005; 19(suppl 1):1–93
4.
Meyer JM, Davis VG, McEvoy JP, Goff DC, Nasrallah HA, Davis SM, Daumit GL, Hsiao J, Swartz MS, Stroup TS, Lieberman JA: Impact of antipsychotic treatment on nonfasting triglycerides in the CATIE Schizophrenia Trial phase 1. Schizophr Res 2008; 103:104–109
5.
Meyer JM, Davis VG, Goff DC, McEvoy JP, Nasrallah HA, Davis SM, Rosenheck RA, Daumit GL, Hsiao J, Swartz MS, Stroup TS, Lieberman JA: Change in metabolic syndrome parameters with antipsychotic treatment in the CATIE Schizophrenia Trial: prospective data from phase 1. Schizophr Res 2008; 101:273–286
6.
Lieberman JA, Stroup TS, McEvoy JP, Swartz MS, Rosenheck RA, Perkins DO, Keefe RS, Davis SM, Davis CE, Lebowitz BD, Severe J, Hsiao JK;; Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) Investigators: Effectiveness of antipsychotic drugs in patients with chronic schizophrenia. N Engl J Med 2005; 353:1209–1223
7.
Kahn RS, Fleischhacker WW, Boter H, Davidson M, Vergouwe Y, Keet IP, Gheorghe MD, Rybakowski JK, Galderisi S, Libiger J, Hummer M, Dollfus S, López-Ibor JJ, Hranov LG, Gaebel W, Peuskens J, Lindefors N, Riecher-Rössler A, Grobbee DE; EUFEST Study Group: Effectiveness of antipsychotic drugs in first-episode schizophrenia and schizophreniform disorder: an open randomised clinical trial. Lancet 2008; 371:1085–1097
8.
Parks J, Svendson D, Singer P, Foti ME (eds): Morbidity and Mortality in People With Serious Mental Illness. Alexandria, Va, National Association of State Mental Health Program Directors (NASMHPD) Medical Directors Council, 2006. www.nasmhpd.org
9.
Cui Y, Blumenthal RS, Flaws JA, Whiteman MK, Langenberg P, Bachorik PS, Bush TL: Non-high-density lipoprotein cholesterol level as a predictor of cardiovascular disease mortality. Arch Intern Med 2001; 161:1413–1419
10.
Bittner V, Hardison R, Kelsey SF, Weiner BH, Jacobs AK, Sopko G: Non-high-density lipoprotein cholesterol levels predict five-year outcome in the Bypass Angioplasty Revascularization Investigation (BARI). Circulation 2002; 106:2537–2542
11.
Sikich L, Frazier JA, McClellan J, Findling RL, Vitiello B, Ritz L, Ambler D, Puglia M, Maloney AE, Michael E, De Jong S, Slifka K, Noyes N, Hlastala S, Pierson L, McNamara NK, Delporto-Bedoya D, Anderson R, Hamer RM, Lieberman JA: Double-blind comparison of first- and second-generation antipsychotics in early-onset schizophrenia and schizo-affective disorder: findings from the Treatment of Early-Onset Schizophrenia Spectrum Disorders (TEOSS) study. Am J Psychiatry 2008; 165:1420–1431
12.
Stroup TS, Lieberman JA, McEvoy JP, Swartz MS, Davis SM, Rosenheck RA, Perkins DO, Keefe RSE, Davis CE, Severe J, Hsiao JK; CATIE Investigators: Effectiveness of olanzapine, quetiapine, risperidone, and ziprasidone in patients with chronic schizophrenia following discontinuation of a previous atypical antipsychotic. Am J Psychiatry 2006; 163:611–622
13.
Weiden PJ, Newcomer JW, Loebel AD, Yang R, Lebovitz HE: Long-term changes in weight and plasma lipids during maintenance treatment with ziprasidone. Neuropsychopharmacology 2008; 33:985–994
14.
Kay SR, Fiszbein A, Opler LA: The Positive and Negative Syndrome Scale (PANSS) for schizophrenia. Schizophr Bull 1987; 13:261–276
15.
Guy W: Clinical Global Impressions. Rockville, Md, National Institute of Mental Health, 1976, pp218–222
16.
Ganguli R: Behavioral therapy for weight loss in patients with schizophrenia. J Clin Psychiatry 2007; 68(suppl 4):19–25
17.
Brar JS, Ganguli R, Pandina G, Turkoz I, Berry S, Mahmoud R: Effects of behavioral therapy on weight loss in overweight and obese patients with schizophrenia or schizoaffective disorder. J Clin Psychiatry 2005; 66:205–212
18.
Abnormal Involuntary Movement Scale (AIMS). Psychopharmacol Bull 1988; 24:781–783
19.
Barnes TR: A rating scale for drug-induced akathisia. Br J Psychiatry 1989; 154:672–676
20.
Simpson GM, Angus JW: A rating scale for extrapyramidal side effects. Acta Psychiatr Scand Suppl 1970; 212:11–19
21.
Diggle PJ, Liang KY, Zeger SL: Analysis of Longitudinal Data. Oxford, England, Oxford Science, 1994
22.
Ware J, Kosinski M, Keller SD: A 12-item short-form health survey: construction of scales and preliminary tests of reliability and validity. Med Care 1996; 34:220–233
23.
Kolotkin RL, Crosby RD: Psychometric evaluation of the Impact of Weight on Quality of Life-Lite Questionnaire (IWQoL-Lite) in a community sample. Qual Life Res 2002; 11:157–171
24.
Marder SR, Essock SM, Miller AL, Buchanan RW, Casey DE, Davis JM, Kane JM, Lieberman JA, Schooler NR, Covell N, Stroup S, Weissman EM, Wirshing DA, Hall CS, Pogach L, Pi-Sunyer X, Bigger JT, Friedman A, Kleinberg D, Yevich SJ, Davis B, Shon S: Physical health monitoring of patients with schizophrenia. Am J Psychiatry 2004; 161:1334–1349
25.
Newcomer JW, Campos JA, Marcus RN, Breder C, Berman RM, Kerselaers W, L'Italien GJ, Nys M, Carson WH, McQuade RD: A multicenter, randomized, double-blind study of the effects of aripiprazole in overweight subjects with schizophrenia or schizoaffective disorder switched from olanzapine. J Clin Psychiatry 2008; 69:1046–1056
26.
Treating Elevated Cholesterol and Heart Disease: The Statins. Consumer Reports Best Buy Drugs. 2007. http://www.consumerreports.org/health/best-buy-drugs/statins.htm
27.
Wu RR, Zhao JP, Jin H, Shao P, Fang MS, Guo XF, He YQ, Liu YJ, Chen JD, Li LH: Lifestyle intervention and metformin for treatment of antipsychotic-induced weight gain: a randomized controlled trial. JAMA 2008; 299:185–193
28.
Wu RR, Zhao JP, Guo XF, He YQ, Fang MS, Guo WB, Chen JD, Li LH: Metformin addition attenuates olanzapine-induced weight gain in drug-naive first-episode schizophrenia patients: a double-blind, placebo-controlled study. Am J Psychiatry 2008; 165:352–358
29.
Jarskog LF, Hamer RM, Catellier DJ, Stewart D, LaVange L, Golden L, Lieberman JA, Stroup TS: Metformin for obesity and metabolic abnormalities in schizophrenia. Neuropsychopharmacology 2010; 35:S225–226

Information & Authors

Information

Published In

Go to American Journal of Psychiatry
Go to American Journal of Psychiatry
American Journal of Psychiatry
Pages: 947 - 956
PubMed: 21768610

History

Received: 8 November 2010
Revision received: 17 February 2011
Revision received: 12 April 2011
Accepted: 29 April 2011
Published online: 1 September 2011
Published in print: September 2011

Authors

Details

T. Scott Stroup, M.D., M.P.H.
From the Columbia University College of Physicians and Surgeons, New York; the Duke University Medical Center, Durham, N.C.; the University of North Carolina School of Public Health, Chapel Hill, N.C.; the University of North Carolina School of Medicine, Chapel Hill, N.C.; Yale University School of Medicine, New Haven, Conn.; and the University of Colorado School of Medicine, Denver.
Joseph P. McEvoy, M.D.
From the Columbia University College of Physicians and Surgeons, New York; the Duke University Medical Center, Durham, N.C.; the University of North Carolina School of Public Health, Chapel Hill, N.C.; the University of North Carolina School of Medicine, Chapel Hill, N.C.; Yale University School of Medicine, New Haven, Conn.; and the University of Colorado School of Medicine, Denver.
Kimberly D. Ring, M.P.H.
From the Columbia University College of Physicians and Surgeons, New York; the Duke University Medical Center, Durham, N.C.; the University of North Carolina School of Public Health, Chapel Hill, N.C.; the University of North Carolina School of Medicine, Chapel Hill, N.C.; Yale University School of Medicine, New Haven, Conn.; and the University of Colorado School of Medicine, Denver.
Robert H. Hamer, Ph.D.
From the Columbia University College of Physicians and Surgeons, New York; the Duke University Medical Center, Durham, N.C.; the University of North Carolina School of Public Health, Chapel Hill, N.C.; the University of North Carolina School of Medicine, Chapel Hill, N.C.; Yale University School of Medicine, New Haven, Conn.; and the University of Colorado School of Medicine, Denver.
Lisa M. LaVange, Ph.D.
From the Columbia University College of Physicians and Surgeons, New York; the Duke University Medical Center, Durham, N.C.; the University of North Carolina School of Public Health, Chapel Hill, N.C.; the University of North Carolina School of Medicine, Chapel Hill, N.C.; Yale University School of Medicine, New Haven, Conn.; and the University of Colorado School of Medicine, Denver.
Marvin S. Swartz, M.D.
From the Columbia University College of Physicians and Surgeons, New York; the Duke University Medical Center, Durham, N.C.; the University of North Carolina School of Public Health, Chapel Hill, N.C.; the University of North Carolina School of Medicine, Chapel Hill, N.C.; Yale University School of Medicine, New Haven, Conn.; and the University of Colorado School of Medicine, Denver.
Robert A. Rosenheck, M.D.
From the Columbia University College of Physicians and Surgeons, New York; the Duke University Medical Center, Durham, N.C.; the University of North Carolina School of Public Health, Chapel Hill, N.C.; the University of North Carolina School of Medicine, Chapel Hill, N.C.; Yale University School of Medicine, New Haven, Conn.; and the University of Colorado School of Medicine, Denver.
Diana O. Perkins, M.D., M.P.H.
From the Columbia University College of Physicians and Surgeons, New York; the Duke University Medical Center, Durham, N.C.; the University of North Carolina School of Public Health, Chapel Hill, N.C.; the University of North Carolina School of Medicine, Chapel Hill, N.C.; Yale University School of Medicine, New Haven, Conn.; and the University of Colorado School of Medicine, Denver.
Abraham M. Nussbaum, M.D.
From the Columbia University College of Physicians and Surgeons, New York; the Duke University Medical Center, Durham, N.C.; the University of North Carolina School of Public Health, Chapel Hill, N.C.; the University of North Carolina School of Medicine, Chapel Hill, N.C.; Yale University School of Medicine, New Haven, Conn.; and the University of Colorado School of Medicine, Denver.
Jeffrey A. Lieberman, M.D.
From the Columbia University College of Physicians and Surgeons, New York; the Duke University Medical Center, Durham, N.C.; the University of North Carolina School of Public Health, Chapel Hill, N.C.; the University of North Carolina School of Medicine, Chapel Hill, N.C.; Yale University School of Medicine, New Haven, Conn.; and the University of Colorado School of Medicine, Denver.
the Schizophrenia Trials Network
From the Columbia University College of Physicians and Surgeons, New York; the Duke University Medical Center, Durham, N.C.; the University of North Carolina School of Public Health, Chapel Hill, N.C.; the University of North Carolina School of Medicine, Chapel Hill, N.C.; Yale University School of Medicine, New Haven, Conn.; and the University of Colorado School of Medicine, Denver.

Notes

Address correspondence to Dr. Stroup ([email protected]).

Funding Information

Within the last 3 years Dr. Stroup has received consulting fees from Janssen and Lilly. Dr. Nussbaum and Ms. Ring report no financial relationships with commercial interests. Dr. McEvoy receives speaking honoraria from Eli Lilly; consultation and honorarium fees for educational lecture for staff from Hoffman LaRoche; advisory fees from Merck; honoraria for speaking and a research grant from Sunovion; and a research grant from GlaxoSmithKline. Dr. Hamer has received advisory or consulting fees, has served on a data and safety monitoring board and an advisory board, or was involved in a contract between the University of North Carolina and the following: Abbott, Acadia, Allergan, Alpharma, AstraZeneca, Cenerx, Corcept, Eli Lilly, EnabledMD, Epix, Johnson and Johnson, Novartis, Pfizer, PureTechVentures, Schwartz, Sanofi-Aventis, Takeda, and Wyeth. Dr. Hamer has served as an expert witness in lawsuits involving Forest, Lundbeck, Sun, Caraco, Teva, Barr, Mylan, Eurand, Cephalon, and Anesta. Dr. LaVange has served on a data and safety monitoring board for MAP Pharmaceuticals, consulted for Parion Sciences, received an honorarium from GlaxoSmithKline, owns stock options from Inspire Pharmaceuticals, and has received research funding from Pfizer and Merck. Dr. Swartz has received research support from Eli Lilly and consulting fees from Novartis. Dr. Rosenheck has received research support from Janssen Pharmaceutica and Wyeth Pharmaceuticals and has consulted to Roche Pharmaceuticals. He has also been a consultant for and is a testifying expert in Jones ex rel. the State of Texas v. Janssen Phamaceutica et al. Dr. Perkins has been a consultant and speaker for Eli Lilly and a consultant for Sunovion. Dr. Lieberman serves on the advisory boards of Bioline, GlaxoSmithKline, Intracellular Therapies, Eli Lilly, Pierre Fabre, and Psychogenics. He does not receive financial compensation or salary support for his participation as an advisor. He receives grant support from Allon, GlaxoSmithKline, Merck, Novartis, Pfizer, Sepracor, and Targacept, and he holds a patent from Repligen.Supported by a grant from the Foundation for NIH (FNIH) and by a contract from NIMH (N01 MH900001). Bristol-Myers Squibb provided aripiprazole and funds to FNIH in support of the study. Bristol-Myers Squibb was not involved in the conduct of the study, data analysis, or the preparation of this manuscript.

Metrics & Citations

Metrics

Citations

Export Citations

If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.

For more information or tips please see 'Downloading to a citation manager' in the Help menu.

Format
Citation style
Style
Copy to clipboard

View Options

View options

PDF/EPUB

View PDF/EPUB

Login options

Already a subscriber? Access your subscription through your login credentials or your institution for full access to this article.

Personal login Institutional Login Open Athens login
Purchase Options

Purchase this article to access the full text.

PPV Articles - American Journal of Psychiatry

PPV Articles - American Journal of Psychiatry

Not a subscriber?

Subscribe Now / Learn More

PsychiatryOnline subscription options offer access to the DSM-5-TR® library, books, journals, CME, and patient resources. This all-in-one virtual library provides psychiatrists and mental health professionals with key resources for diagnosis, treatment, research, and professional development.

Need more help? PsychiatryOnline Customer Service may be reached by emailing [email protected] or by calling 800-368-5777 (in the U.S.) or 703-907-7322 (outside the U.S.).

Media

Figures

Other

Tables

Share

Share

Share article link

Share