Patients with delusional infestation (DI) frequently refuse to be treated with psychoactive drugs. In the past, pimozide was commonly used as a first-line agent but is now prescribed more rarely. Risperidone was first used to treat DI in 1995. A recent review identified 12 studies that evaluated the use of risperidone in 43 patients with DI.

To study the characteristics of and therapeutic results in patients with DI treated with risperidone at a university medical centre in São Paulo, Brazil.

We performed a retrospective study of patients with DI treated with risperidone at a dermatological university clinic since 2016. Records were reviewed for personal data and findings related to treatment.

Twenty-seven patients were studied (20 women and 7 men). The maintenance dose of risperidone varied from 1 mg three times weekly to 8 mg daily. Control of symptoms was achieved in the majority of patients. A reduction in dosage due to side-effects was seen in four patients; risperidone had to be switched to another antipsychotic in three cases, despite a good response. Only one patient did not respond to risperidone.

Risperidone is an effective, well-tolerated and safe treatment for delusional parasitosis. Adequate follow-up is mandatory in order to obtain long-term control of symptoms.