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Weight Gain is Potential Problem in Patients Switched from Risperidone to Olanzapine

Significant increases in weight and body mass index are observed in patients whose antipsychotic medication is switched from risperidone to olanzapine, but not in those switched from olanzapine to risperidone, say researchers.

The use of atypical antipsychotics has gained popularity due to their proven efficacy in the treatment of schizophrenia and other disorders and their decreased incidence of extrapyramidal side effects as compared to older treatments. However, this class of drugs has also been associated with metabolic adverse effects including dyslipidaemia, poor glycaemic control, and weight gain.

Due to commonplace switching from one atypical antipsychotic to another in the management of schizophrenia, more information is required on the effects of switching on these metabolic adverse effects.

L Douglas Ried, PhD, and colleagues at the University of Florida and the Malcom Randall Veterans Affairs Medical Centre, Gainesville, Florida, United States, therefore analysed the effect of switching atypical antipsychotic regimens on patient weight.

The retrospective study included 86 patients (75 men and 11 women, average age 53) who were initially treated with either risperidone or olanzapine (duration >60 days) and then switched to the other medication (>60 days). Weight and/or BMI measurements were analysed before and after the regimen change.

The study found that patients switched to olanzapine showed a significant increase in average weight and BMI. Specifically, these patients gained on average 2.3 kg or 2.8% of their baseline weight (p=.01) and saw an average 0.8 kg/m² or 3.0% (p=.02) increase in BMI. Furthermore, 1 in 4 of these patients gained weight in excess of 7% of their baseline body weight.

In contrast, patients switched to risperidone did not show significant changes in weight or BMI. Moreover, these patients showed a trend toward decreased weight and BMI. Despite this generalised effect, 1 in 8 of these patients gained over 7% of their baseline body weight.

Further analysis also indicated that all patients showed some weight gain in the first 6 months, though less weight gain was seen in the switch to risperidone. Patient weight after 6 months was significantly lower than that measured in the first 6 months (p=.04).

Dr. Ried concludes that "even after patients' baseline weights were controlled, those switching from risperidone to olanzapine were more likely to gain weight." He therefore recommends that "further investigations should examine whether additional weight gain caused by atypical antipsychotic treatment further jeopardizes this already at risk population for severe comorbid conditions such as hypertension, coronary artery disease, and type 2 diabetes."

Dr. Ried adds that "practitioners may want to actively consider strategies for maintaining or losing weight such as support groups, dietary changes, and reminders from primary care providers."

The Annals of Pharmacotherapy 2003;37:10:1381-1386. "Weight change after an atypical antipsychotic switch"

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