The atypical antipsychotics risperidone, olanzapine, quetiapine, ziprasidone,and aripiprazole have become first-line treatment for schizophrenia because they reduce the positive symptoms of psychosis but do not have a high incidence of extrapyramidal symptoms. However, these agents, like other antipsychotics, may take as long as 16 or more weeks to produce a response, and even with prolonged treatment are unlikely to evoke responses greater than 50% improvement in symptoms. This has led to the experimental use of high atypical antipsychotic doses, antipsychotic polypharmacy, and augmentation with other psychotropic drugs, all of which occur commonly in clinical practice. This article reviews the current evidence for these increasingly common means of treating
schizophrenia and psychosis, with particular emphasis on polypharmacy and augmentation. To date, there are only two controlled studies of antipsychotic polypharmacy involving an atypical antipsychotic; the rest of the data are uncontrolled trials and case reports that describe a mixture of positive and negative findings. One multicenter, double-blind trial shows a faster onset of action when divalproex is added to risperidone or olanzapine than with antipsychotic monotherapy. A small double-blind study demonstrates efficacy when lamotrigine is added to clozapine. The rest of the data on augmentation with anticonvulsants are uncontrolled, and most report adverse effects. With the exception of divalproex, there are currently no compelling data to justify the use of antipsychotic polypharmacy or augmentation. Existing evidence suggests that the best treatments for schizophrenia and psychosis may be long-term trials of a sequence of atypical antipsychotic monotherapies at therapeutic doses.
Increasing the dose in patients with partial responses or breakthrough symptoms is faster and easier than switching to another agent, and it is possible that it would result in improved efficacy. There are also some patients who may be
rapid metabolizers, and thus require higher doses than the average patient. However, although some patients may benefit from higher doses, this method of treatment can
increase the risk of side effects, especially motor side effects. Positron emission tomography (PET) data demonstrate that dopamine 2 (D2) receptor occupancy of 70% is necessary for therapeutic benefits, while occupancy greater than 80% is associated with extrapyramidal symptoms [34]. Doses at the upper end of the recommended range for the first-line antipsychotics may already result in 80% occupancy of D2
receptors in the nigrostriatal pathway [35], so that doses above those ranges are more likely to induce EPS. In particular, the risk of EPS with risperidone is dose-
dependent and may even increase above 4 mg/day
In summary, there is currently no compelling evidence to support long-term antipsychotic polypharmacy. There are few theoretical benefits and many theoretical detriments. Although individual patients may respond to antipsychotic
polypharmacy without side effects, adequate trials have not yet determined the costs versus the benefits of this option.
The evidence for augmentation of atypical antipsychotics varies depending on the particular agent. Controlled studies with conventional antipsychotics suggest that augmentation with benzodiazepines is most likely useful as an acute treatment for patients with agitation and hostility, but controlled studies do not exist for atypical antipsychotics. As mentioned earlier, a multicenter double-blind study demonstrates the safety and efficacy of only one augmenting agent in schizophrenia, namely divalproex [96]. Controlled studies combining divalproex and an atypical antipsychotic also show additive benefits in bipolar disorder, strengthening the appeal of this particular augmenting strategy [167-168]. Unfortunately, there are no controlled data for augmentation of atypical antipsychotics with other anticonvulsants even though this is a frequent and expensive practice, especially with gabapentin. Thus, the evidence currently suggests that divalproex is perhaps the best evidence-based augmentation option when multiple monotherapies fail
A Critical Review of Atypical Antipsychotic Utilization: Comparing
Monotherapy with Polypharmacy and Augmentation
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