Letters to the Editor
Reconsidering Pimozide for New-Onset Delusions of Parasitosis
Dear Editor:
For the last few decades, pimozide has been the standard therapy for delusional parasitosis. However, the latest evidence suggests that the newer atypical antipsychotics should be first-line therapy, owing to their better side effect profile and greater efficacy (1–6).
We report the case of a patient with new-onset delusional parasitosis who was begun on olanzepine but whose symptoms resolved with pimozide.
Case Report
Mr W, a white man aged 41 years, presented to emergency after experiencing tactile and visual hallucinations for 3 weeks. He described a “chain-saw worm,” a “shark bug,” and beetles poking their eyes out of his fingernails and boring holes into the skin of his arms, legs, and penis. To help decrease further infestation, he showered for 2 hours and prepared his bed for 6 hours daily.
His medical history is complex but not progressive, including chronic ankylosing spondylitis, Crohn’s disease, and hepatitis C. He has a history of child abuse and treated chronic depression. He had an episode of postoperative delirium but no other prior psychotic symptoms. His 9 daily medications included prednisone, ranitidine, sertraline, and high dosages of morphine.
Because of its deliriogenic effects, Mr W’s morphine was decreased from 360 mg daily to 300 mg daily. He was begun on olanzepine 2.5 mg daily, which was increased to 10 mg daily within 3 days. He remained on the higher dosage of olanzepine for 1 week with no change in his symptoms or agitation. At this point, he met the “1-month” criteria for delusional disorder, somatic type. He was switched to pimozide 2 mg daily. Within 10 days, complete resolution of his symptoms occurred. He was discharged home on pimozide, which was tapered to 1 mg after 1 month. At 6 weeks, he had no recurrent symptoms. The pimozide will be discontinued at 2 months.
Discussion
Pimozide therapy was first reported to be beneficial for somatic delusions in 5 patients in 1975 (7). Several small, noncontrolled studies have reported its benefits, which include recovery from delusions of para- sitosis in up to 90% of patients (1).
Newer studies suggest that atypical antipsychotics are equally effective (2). The serotonergic activity of atypicals is suggested to have the additional benefit of reducing the obsessive–compulsive and self-mutilatory features of somatic delusions (2).
Case reports have found response to risper- idone in various somatic delusional disorders (4–6). In a 1997 study, treatment with risperidone eliminated symptoms in 3 patients with long histories of delusions of parasitosis who did not respond to halo- peridol or pimozide (3). Recently, treatment with low-dosage olanzapine led to complete resolution of symptoms in a case of delusions of infestation (8). Most patients in these studies presented with long-standing histories, having experienced delusions for months to years.
In our case, the older, typical neuroleptic pimozide was effective in treating the new- onset delusion of infestation. More rigorous study into the benefits of treatment with pimozide vs the newer neuroleptics would be useful, not only for treating somatic delusions but also for patients presenting with early symptoms.
References
1. Driscoll M, Rothe M, Grant-Kels J, Hale M. Delusional parasitosis: a dermatological and pharmacological approach. J Am Acad Dermatol 1993;29:1023–33.
2. Elmer K, George R, Peterson K. Therapeutic update: use of risperidone for the treatment of monosymptomatic hypochondriacal psychosis.
J Am Acad Dermatol 2000;43:683–6.
3. De Leon O, Furmaga K, Canterbury A, Bailey L. Risperidone in the treatment of delusions of infestation. Int J Psychiatry Med 1997;27:403–9.
4. Gallucci G, Beard G. Risperidone and the treatment of delusions of parasitosis in an elderly patient. Psychosomatics 1995;36:578–80.
5. Kitamura H. A case of somatic delusional disorder that responded to treatment with risperidone [letter]. Psychiatry Clinical Neurosci 1997;51:337.
6. Songer D, Roman B. Treatment of somatic delusional disorder with atypical antipsychotic agents. Am J Psychiatry 1996;153:578–9.
7. Riding B, Munro A. Pimozide in monosymptomatic psychosis. Lancet 1975;1:1385–6.
8. Weintraub E, Robinson C. A case of monosymptomatic hypochondriacal psychosis treated with olanzapine. Ann Clin Psychiatry 2000;12:247–9.
Melanie Makhija, BSc, MSc
Shree Bhalerao, BSc, BA, PGD, MD, FRCPC
Toronto, Ontario
|
