Antipsychotic drug combinations are often given to patients early in treatment

Patients with schizophrenia and other mental illnesses are commonly prescribed high dose combinations of antipsychotic drugs earlier than recommended by some guidelines, finds a new study in the March issue of General Hospital Psychiatry.

Antipsychotic polypharmacy (APP) is the co-prescription of more than one antipsychotic drug for one patient.  APP is not unusual, but there is scarce evidence about how these drugs interact and whether combining them increases the risk of chronic side effects such as diabetes.

“The use of multiple anitipsychotic drugs has become a common practice mostly based on practitioners’ own experiences. That’s because there are only a few published studies and they show contradictory outcomes,” said lead author Amaia López de Torre, PharmD, with Galdakao-Usansolo Hospital, Galdakao in Spain. She said until further clinical trials are available practitioners should be aware of potential adverse effects and interactions derived from APP, especially in elderly patients.

Thomas N. Wise, M.D., professor of psychiatry at Johns Hopkins University School of Medicine and chairman of Inova Fairfax Hospital’s department of psychiatry, said, “The study is excellent, and relevant and transfers to our experiences too, that antipsychotic drugs are often given in combination.”

The researchers collected data over one day, when 201 patients were admitted to the Hospital Psiquiatrico de Alava, a psychiatric hospital in Vitoria-Gasteiz, Spain. Of the 201 patients, 172 patients had been prescribed antipsychotics. 47 percent of those patients were prescribed more than one drug. Four of the most common two-drug combinations had no supporting clinical evidence for their use.  The researchers could find no supporting data for three-drug combinations, which were prescribed to 19 patients. Moreover, 12 patients were prescribed drug combinations with known negative interactions.

The authors explained several possible rationales for APP. For example, prescribing lower doses of different drugs may relieve symptoms with fewer side effects than when a higher-dose single drug, or monotherapy, is used.  The researchers also concluded that obtaining detailed patient histories, informed consent from patients/representatives and careful drug and side-effect monitoring is recommended before and following polypharmacy treatment.

Wise cautioned, “There is a myth that monotherapy may be a better approach than giving a combination of antipsychotic drugs to a patient.  That may be true in an ideal world, but in the real world, where efficacy and effectiveness of treatment is mandatory, a combination of drugs is often necessary because each has different properties.”