Delusional Parasitosis Successfully Controlled with Risperidone – Two Case Reports

Background: Delusional parasitosis is a psychiatric disorder in which the patient holds the fixed delusional believe to be infested with parasites. Pimozide is the most commonly used treatment modality for the therapy of delusional parasitosis. However, because of the wide spectrum of side effects of pimozide, some authors tested the benefits of newgeneration antipsychotics to patients suffering from delusional parasitosis. Case Reports: We present two patients (one male and one female) who were suffering from delusional parasitosis and were successfully treated with risperidone. The first patient presented with tactile hallucinations, paresthesia and pruritus located mainly on the parietal aspect of the scalp attributed to parasites. He had previously been treated with haloperidol. Although some improvement was observed, treatment was interrupted because of extrapyramidal side effects. Next, olanzapine was tried, but without any significant improvement. Finally, the patient was put on risperidone which resulted in a remarkable reduction of psychotic symptoms. The second patient presented with pruritus and tactile hallucinations on the scalp and in the ears due to the misbelief to be infected with parasites. Delusional parasitosis was diagnosed and after psychiatric consultation risperidone was given at a dose of 1-3 mg/d. After 2.5 months the symptoms completely disappeared. Today, 1 year after beginning of risperidone treatment, the patient is still on 1 mg/d of the drug and completely free of symptoms. Conclusion: Based on the presented patients we believe that risperidone is an effective and well-tolerated agent for the therapy of delusional parasitosis. Therefore, risperidone should be considered as one of the possible treatment modalities for delusional parasitosis.