Substance abuse and dependence occur at a high prevalence in schizophrenia [ 52 ]. The combination of a severe mental illness and a substance use disorder (SUD), commonly described as “dual diagnosis”, is associated with increased morbidity, poorer functioning, decreased adherence to medication, and higher rates of relapse compared to either disorder individually [ 53 ]. Integrated treatment strategies for dual diagnosis that include pharmacotherapy have been developed for individuals with schizophrenia and SUDs. (See "Co-occurring schizophrenia and substance use disorder: Epidemiology, pathogenesis, clinical manifestations, course, assessment and diagnosis" .)
This topic addresses the use of LAI antipsychotics in the treatment of schizophrenia. The pharmacology, administration, comparative side effects and treatment of schizophrenia with standard (non-LAI) antipsychotics are discussed separately as is the management of antipsychotic side effects. The epidemiology, clinical manifestations, and diagnosis of schizophrenia are discussed separately. (See "Pharmacotherapy for schizophrenia: Acute and maintenance phase treatment" and "First-generation antipsychotic medications: Pharmacology, administration, and comparative side effects" and "Second-generation antipsychotic medications: Pharmacology, administration, and side effects" and "Pharmacotherapy for schizophrenia: Side effect management" and "Schizophrenia in adults: Clinical manifestations, course, assessment, and diagnosis" and "Schizophrenia in adults: Epidemiology and pathogenesis" .)
Nonadherence to medications is a significant problem; in a recent study, 74 percent of patients discontinued their medication within 18 months. 16 Nonadherence often leads to relapse of symptoms. Atypical antipsychotics were initially thought to help with adherence because of their lower rate of neurologic side effects. However, meta-analyses have found that drop-out rates and relapse prevention are no better with atypical antipsychotics than with neuroleptics. 17 , 18 Meta-analyses also have found that in terms of symptom scores and drop-out rates, atypical antipsychotics are better than high dosages (., more than 12 mg per day) of haloperidol (Haldol); there was no advantage when the dosage of haloperidol was less than 12 mg per day. 17 In other words, many of the perceived benefits of atypical antipsychotics actually were a result of the excessive doses of first-generation antipsychotics that were used for comparison in randomized trials. 17 Evidence suggests that delays in initiating therapy with antipsychotics may result in a lifetime deleterious effect on psychotic episodes and social adjustment. 19 , 20 If initiation of antipsychotic therapy is delayed because of limited psychiatric resources, family physicians should consider starting medications instead.