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The prevalence of substance abuse (30% to 50%) among persons with schizophrenia is significantly higher than for those in the general population (1,2). Dual-diagnosed people are more likely to experience side effects leading to noncompliance, to have poor response to traditional antipsychotics, and to have high rates of rehospitalization (3–6). For patients discharged on traditional antipsychotics, substance abuse is one of the most significant and predictive reasons for readmission (7,8). Identifying effective treatments for this group may improve the outcome for a significant percentage of those who suffer from this devastating illness. There is growing evidence that second-generation anti- psychotics (SGAs) may offer effective clinical treatment for schizophrenia patients with comorbid substance abuse. Treatment with SGAs is associated with similar response rates between patients with and without substance abuse histories (9–11). These medications are associated with better compliance rates than are traditional agents, as well as with lower rates of rehospitalization (12–14). Further evidence indicates that clozapine treatment may actually reduce the use of drugs and alcohol (15–17). These findings are encouraging; thus, continuing to assess the treatment of dual diagnosis patients is indicated. In this study, we examined the readmission rates of discharged patients taking clozapine over time. Those with histories of substance abuse were compared with those without prior abuse. MethodsThis study measured outcomes for patients discharged from a research unit between April 1991 and March 1996. A total of 45 patients were started on clozapine and subsequently discharged. All patients were diagnosed with schizophrenia, according to DSM-III-R diagnostic criteria. In addition, all subjects met criteria for treatment resistance (18). Substance abuse was diagnosed according to criteria for DSM-III-R. Computerized hospital records were evaluated for readmission status, and telephone calls were made to patients’ families and supervised housing caregivers for hospitalization and medication status after discharge. Informed consent was obtained, and there were no patients lost to follow-up. Of the 45 patients, 43 (96%) were discharged to supervised housing where medication intake was monitored. All supervised housing caregivers were blind to the study. The time course to rehospitalization was measured by the product-limit (Kaplan–Meier) survivor analysis and compared using the Log-Rank Chi Square statistic. All variables were evaluated by two-tailed independent t-tests. A significant alpha level was considered 0.05. Pearson’s Correlation Coefficient was used to determine correlation between the rehospitalization rate and the baseline measures, such as demographic variables and Brief Psychiatric Rating Scale (BPRS) scores. ResultsNineteen patients discharged on clozapine were classified as having a history of substance abuse by stringent DSM-III-R criteria. An additional 26 patients discharged on clozapine, lacking prior substance abuse, were compared with those who had a history of abuse. All but 2 patients were discharged to structured supervised housing programs, which provide supervision of medication and participation in a psychiatric rehabilitation program. The 2 groups did not differ significantly on demographic variables. Severity of illness at discharge was significantly lower in the group with substance abuse histories (Table 1).
The groups did not differ significantly with respect to time course to readmission (c2 = 0.26, df 1, P = 0.61, log-rank test); however, those with a history of abuse did as well in terms of remaining in the community following discharge as did the group without prior abuse histories. At 5 years following discharge, the rate of readmission was 45% for prior substance abuse patients (95%CI, 13% to 77%) and 44% for patients without histories (95%CI, 34% to 54%). One-year readmission rates were 21% (95%CI, 7% to 39%) and 23% (95%CI, 7% to 39%) in patients with and without a history of substance abuse, respectively (Figure 1). We saw a lower rate of rehospitalization with older ages in both the total group (r = 0.37, P = 0.01) and the non–substance abuse (NSA) group (r = 0.43, P = 0.03). In the substance abuse (SA) group, a greater number of prior rehospitalizations was correlated with an increasing risk of rehospitalization (r = 0.60, P = 0.01). The rates of medication discontinuation following discharge were 5/26 (19%) in the NSA group and 4/19 (21%) in the SA group and were not found to be associated with a higher rate of rehospitalization. Figure 1 Time course to readmission in patients discharged on clozapine
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