Recent clinical and epidemiological studies have estimated that 20 to 58percnt; of patients with schizophrenia also have a diagnosis of substance abuse (i.e. have a lsquo;dual diagnosisrsquo;). In these patients, alcohol (ethanol), cannabis and psychostimulants are the drugs that are preferentially abused. Compared with other schizophrenic patients, those with a dual diagnosis were found to show more positive symptoms, and to have a higher risk for psychotic relapse and noncompliance with drug treatments.Benzodiazepines, and possibly carbamazepine, are recommended for detoxification in patients with dual diagnosis. In the initial treatment of psychosis in these patients, potent antipsychotics that have few anticholinergic adverse effects, such as haloperidol, should be given. For long term treatment, depot antipsychotics can be used to increase compliance rates. Since patients with a dual diagnosis are especially susceptible to tardive dyskinesia, clozapine is a possible alternative to other antipsychotics. Antiparkinsonian medication and antidepressants are other drugs to be considered.There is some evidence that flupenthixol (not available in the US) counteracts both psychosis and the craving for alcohol and cocaine. Disulfiram should be avoided for relapse prevention because of the risk of exacerbation of psychosis. Methadone or specific anticraving drugs such as naltrexone may be used in some patients.
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