Authors' reply

Narayan et al suggest that the pharmacokinetics (half-life of 60–80 h) and side-effect profile of aripiprazole may make it particularly interesting for the treatment of primary delusional parasitosis where adherence to and engagement with treatment are the most significant challenges. They mention a case report of an 85-year-old woman with primary delusional parasitosis, who fully responded to aripiprazole. ¹ It is interesting that our own systematic review showed that the best response rates were achieved with first-generation depot antipsychotics. ²

However, other first-generation antipsychotics with relatively long half-lives did not differ from those with shorter half-lives. Experience with second-generation antipsychotics with long half-lives is limited to one case with partial remission to sertindole ³ and one recent case treated with paliperidone. ⁴ The level of efficacy of second-generation antipsychotics in delusional parasitosis is less than certain. Our own review showed that only 25% of patients treated with a second-generation antipsychotic achieved full remission in primary delusional parasitosis. The side-effect profile of aripiprazole may be advantageous with regard to the development of metabolic syndrome, but this is often less important in delusional parasitosis because of the often short period of time that patients agree to take medication. Furthermore, the common side-effect of insomnia is a real problem with aripiprazole in a patient group that already suffers from agitation and insomnia because of persistent itching.

We therefore do not agree that the current evidence available for aripiprazole makes it the substance of choice among second-generation antipsychotics for primary delusional parasitosis despite its favourable pharmacokinetic profile and low risk of metabolic and cardiac complications. There are substantially more successful reports on risperidone (more than 30) and olanzapine (more than 15) as well as our own positive experience with amisulpride than case reports on aripiprazole in both primary and secondary delusional parasitosis. However, clinical studies, not case reports, will be needed to further establish second-generation antipsychotics in delusional parasitosis and show their individual effects in this syndrome.