Management of Antipsychotic-Induced Weight Gain

Introduction to Metformin Therapy

The American Psychiatric Association recommends adding metformin 500 mg once daily, gradually titrating to 1000 mg twice daily, as the first-line pharmacological intervention to attenuate antipsychotic-associated weight gain 1
Metformin is specifically recommended to be offered concomitantly with antipsychotics that have poor cardiometabolic profiles to attenuate potential weight gain 1

Aripiprazole generally demonstrates a lower risk for weight gain compared to other antipsychotics, but individual patients can still experience significant weight gain, making metformin an appropriate intervention 2, 3
Metformin achieves approximately 3% weight loss, with 25-50% of participants achieving at least 5% weight loss 1
Doses greater than 1500 mg are associated with the greatest weight loss 1
If metformin is ineffective after 3-6 months, consider switching from aripiprazole to lurasidone or ziprasidone, which are the most weight-neutral antipsychotics in the class 1, 2, 3

Before initiating metformin, assess renal function, as metformin should be avoided in patients with renal failure 1
Obtain baseline BMI, waist circumference, blood pressure, HbA1c, glucose, and lipids before starting metformin 1
Annual liver function tests, HbA1c, renal function, and vitamin B12 levels are recommended during metformin therapy 1
Implement lifestyle modifications concurrently with metformin, including dietary counseling and physical activity promotion 1

GLP-1 receptor agonists may be considered for weight management, but current global shortages exist and insurance coverage is often restricted to FDA-approved diabetes indications 1
Orlistat could be considered as an alternative if metformin fails, particularly if the patient has constipation, as it blocks absorption of approximately 30% of ingested fat 6, 7, 8
Liraglutide (Saxenda) is effective for weight management, but cost and insurance coverage issues make this a second- or third-line option 1, 6