Clozapine for Schizophrenia: State Variation in Evidence-Based Practice

Clozapine is the only antipsychotic with known efficacy in treatment-resistant schizophrenia. Although 20% to 30% of individuals with schizophrenia have treatment-resistant conditions, clozapine accounts for only about 5% of their antipsychotic starts (1).We updated our previous analysis (2001–2005) by examining more recent (2006–2009) trends and patterns across 46 state Medicaid programs.

Overall, clozapine accounted for 4.8% (95% confidence interval [CI]=4.8%–4.9%) of antipsychotic use in schizophrenia, with a slight decline during this period: 5.7% (CI=5.6%–5.8%) in 2006; 4.9% (CI=4.8%–5.0%) in 2007; 4.6% (CI=4.5%–4.6%) in 2008; and 4.3% (CI=4.2%–4.4%) in 2009. Figure 1 shows substantial interstate variation. Clozapine was least commonly used in the Deep South and more commonly used in New England, the Rocky Mountain West, and Washington. The highest rate was in South Dakota (15.6%, CI=14.0%–17.2%) and the lowest in Louisiana (2.0%, CI=1.9%–2.2%).

Fiscal stress has been linked to lower clozapine use (2), as has inadequate staffing to monitor clozapine (3). The state variations are broadly consistent with known variations in overall Medicaid spending for disabled beneficiaries. Patient reluctance about blood monitoring and concerns over tolerability are unlikely to explain the variation.

These findings underscore the need to determine the extent to which state variation can be explained by local practice environments or state policy factors. Interventions and policies are needed to promote appropriate clozapine treatment of Medicaid-insured patients with treatment-resistant schizophrenia.