Atypical Antipsychotics
In contrast to concerns that conventional antipsychotics may worsen substance abuse, a number of (still preliminary) studies suggest that some of the second-generation (atypical) agents may be helpful for these patients (see reference
28 for detailed review). For example, there have been reports that for patients treated with clozapine and olanzapine, overall outcomes during treatment are as good among those who have a co-occurring substance use disorder as those who do not. Some researchers have suggested that the lower incidence of neurologic side effects produced by the atypical antipsychotics, along with the possibility that these agents may be more likely to decrease negative symptoms, make them a logical choice for patients with co-occurring substance use disorder (even though parameters of the metabolic syndrome must be monitored while using these agents).
Regarding nicotine, several controlled studies (reference
29, for example) have indicated that smoking cessation interventions may be more effective in patients with schizophrenia who are treated with atypical rather than conventional antipsychotics. McEvoy and colleagues prospectively studied patients switching from conventional antipsychotics to clozapine and observed spontaneous reductions in cigarette smoking, in both a small (N=12) and a larger (N=55) group of patients (review in reference
28 ).
A substantial portion of the available data concerning the effects of atypical antipsychotics on substance use in patients with schizophrenia is from clozapine studies. Initially, case reports and series noted reduced use (with frequent abstinence) and reduced craving for substances while taking clozapine. Two retrospective surveys of approximately 35 patients each (one by our group) reported significant reductions in alcohol and other substance abuse. These findings were supported by data from a prospective trial indicating that 11 of 16 patients (70%) with co-occurring substance use disorder and schizophrenia reduced or stopped using substances during a 12-week prospective trial of clozapine (review in reference
28 ).
Our group also reported other data supporting this unusual effect of clozapine. In a naturalistic study of 151 patients with schizophrenia and substance use disorder who were followed longitudinally for more than 3 years
(30), we found that the 36 patients treated with clozapine were more than twice as likely to attain full remission of alcohol abuse than those treated with conventional antipsychotics (79% versus 34%). In a 10-year follow-up report on the same patient sample
(31), we noted that in patients who attained remission, use of clozapine was associated with a markedly reduced relapse rate over the subsequent year (8% of the clozapine group versus 40% of the conventional antipsychotic group). We have proposed that the effect of clozapine on substance use in these patients is related to clozapine’s broad-spectrum pharmacologic effects (i.e., its weak antagonism at the dopamine D
2 receptor and its potent blockade of the noradrenergic α
2 receptor, coupled with its ability to release norepinephrine in the brain), which result in an amelioration of the brain reward circuit deficiency in these patients
(6,
12) . However, despite the strong suggestions these studies offer on clozapine’s potential, none were prospective randomized controlled trials, and thus the evidence about clozapine’s value for these patients remains preliminary.
A number of other, more recently developed atypical antipsychotics have also been assessed in patients with co-occurring substance use disorder, but there is even less information about them than about clozapine. In a randomized, prospective study comparing risperidone and haloperidol, risperidone treatment decreased cue-craving and substance abuse relapse in patients with schizophrenia and co-occurring cocaine dependence
(32) . However, our group, in a retrospective study of 41 patients with schizophrenia and co-occurring alcohol or cannabis use disorder
(33), noted that abstinence rates were considerably higher among patients treated with clozapine (54%) than among those treated with risperidone (12.5%). Moreover, a large (N=249) retrospective chart review of Department of Veterans Affairs (VA) patients
(34) found that after confounding factors were controlled for, there were no differences in improvement on Addiction Severity Index scores between patients treated with atypical antipsychotics (mostly risperidone and olanzapine) and those treated with conventional antipsychotics.
Although case reports and one open-label trial (review in reference
28 ) have suggested that olanzapine may be associated with a reduction in substance use, results of randomized controlled trials have been mixed. Smelson and colleagues
(35) reported reduced cue-craving and reduced cocaine-positive urine screens with olanzapine compared with haloperidol, but Sayers and colleagues
(36) reported negative findings for olanzapine compared with haloperidol. Our group reported that although the rate of substance use appeared to decrease in patients treated with olanzapine, the same decreased rate was observed in patients treated with conventional antipsychotics (see reference
28 ). Finally, as noted above, in the large VA chart review, no differences were observed in improvement in substance abuse measures between those taking olanzapine or risperidone and those taking conventional antipsychotics
(34) .
In two open trials, treatment with quetiapine was associated with reductions in one of several measures of substance abuse in 24 patients with schizophrenia spectrum disorders and with decreased stimulant craving but not decreased stimulant use in 24 patients with co-occurring disorders whose medications were switched from conventional antipsychotics (see reference
28 ). In two small pilot studies, aripiprazole has been reported to decrease craving for and use of alcohol and cocaine (see reference
28 ). To our knowledge, there are no reports on the use of ziprasidone in this population.
Clearly, further studies of the effects of the various atypical antipsychotics will be needed before clear recommendations can be made on optimal pharmacologic management for patients with schizophrenia and co-occurring substance use disorder.
Adjunctive Alcohol Use Disorder Treatments
Three medications have been approved in the United States for the treatment of alcohol use disorders—disulfiram, naltrexone, and acamprosate. While disulfiram has been available for decades as a treatment for alcoholism and has been used safely in patients with schizophrenia and alcohol use disorders, its use in this patient group has been quite limited. This may be due to concerns about its potential ability to increase psychosis and about its potential liver toxicity. However, a recent retrospective study of disulfiram in 33 patients with alcohol use disorder and severe mental illness found that 64% developed a sustained remission from their alcohol use disorder without evidence of exacerbation of psychosis
(39) . A recent report
(40) on the use of disulfiram in a large group of patients (N=250) with a variety of mental illnesses and co-occurring alcohol dependence (66 of whom had a diagnosis of a psychotic spectrum disorder) demonstrated that disulfiram was well tolerated and more effective than placebo in reducing alcohol use in this population, without worsening psychosis or causing liver toxicity.
Naltrexone, which has been shown to reduce drinking in patients with primary alcohol use disorders, has shown promise in patients with co-occurring schizophrenia or other psychotic disorders and alcohol use disorder. In two randomized controlled trials, one with 31 patients with schizophrenia, the other with 66 patients with a psychotic spectrum disorder, alcohol use decreased more in patients treated with adjunctive naltrexone than in those treated with adjunctive placebo
(40,
41) . Continued studies will be needed to fully delineate the extent of this effect and to ascertain whether naltrexone’s potential liver toxicity will be problematic for routine use in this population. The availability of long-acting injectable naltrexone will provide another potential therapeutic option for these patients.
Two other medications may be of interest in the future for this population. Acamprosate, an agent with glutamatergic effects, was recently approved for use in the treatment of alcoholism. However, we are not aware of any studies of this medication in patients with schizophrenia. Finally, the anticonvulsant topiramate has shown promising results in patients with alcoholism. At the time of this writing, case reports suggest that topiramate may also have a beneficial effect on alcohol use in patients with schizophrenia (review in reference
28 ).