Bugs on her skin—but nobody else sees them

The SGAs risperidone, olanzapine, aripiprazole, quetiapine, paliperidone, and ziprasidone have also been used in case reports.^6,8,10,11 Olanzapine and risperidone appear to have the most robust evidence supporting their use. Long-acting injectable antipsychotics, such as long-acting risperidone and paliperidone palmitate, have been used with success.^8,10 A systematic review did not find any evidence to support that any one antipsychotic was superior to another, nor was there a difference in response rate to FGAs or SGAs.⁶ In a case series, Boggild et al¹¹ found that combination therapy with an antidepressant and a low-dose high potency antipsychotic lead to improvements in symptom severity.

When selecting antipsychotic therapy for a patient diagnosed with delusional parasitosis, consider patient-specific factors, such as age, medication history, comorbidities, and the adverse-effect profile of the medication(s). These medications should be started at a low dose and titrated based on efficacy and safety. The optimal duration of therapy varies by patient. Patients should continually be assessed for possible treatment discontinuation, although if therapy is tapered off, patients need to be closely monitored for possible relapse or recurrence of symptoms.

Ms. L received perphenazine titrated up to 24 mg/d for the treatment of delusional parasitosis. The maximum dose used for Ms. L was higher than those used in previous reports, although she appeared to tolerate the medication well and respond rapidly. Her symptoms showed improvement within 1 week. Importantly, in published case reports, patients have been resistant to the use of psychotropic medications without other treatment modalities (eg, psychotherapy, various behavioral approaches). We conclude that Ms. L’s response was attributable to the use of the combination of psychotherapeutic techniques and the effectiveness of perphenazine and venlafaxine.

Bottom Line

Managing patients with primary delusional parasitosis can be challenging due to the fixed nature of the delusion. A combination of antipsychotics and psychotherapeutic techniques can benefit some patients. The optimal duration of treatment varies by patient.

Related Resource

• Trenton A, Pansare N, Tobia A, et al. Delusional parasitosis on the psychiatric consultation service-a longitudinal perspective: case study. BJPsych Open. 2017;3(3):154-158. 

Drug Brand Names

Aripiprazole • Abilify
Haloperidol • Haldol
Olanzapine • Zyprexa
Paliperidone • Invega
Paliperidone palmitate • Invega Sustenna
Perphenazine • Trilafon
Pimozide • Orap
Quetiapine • Seroquel
Risperidone • Risperdal
Venlafaxine • Effexor  
Ziprasidone • Geodon