Aripiprazole treatment in a case of amphetamine-induced delusional infestation

Delusional infestation is a relatively rare psychiatric condition characterized by the hypochondriacal delusion that the patient is infested with insects despite objective evidence to the contrary. It can be categorized into a primary form without any underlying cause, and a secondary form considered to be related to mental illnesses, general medical conditions, organic brain diseases and drug use (Freudenmann and Lepping, 2009). We present a young man with delusional infestation caused by amphetamine use who was successfully treated with aripiprazole.

A 26-year-old male with a six-year history of amphetamine abuse presented to our dermatology department for generalized pruritus caused by ‘bugs’ which he believed had been burrowing into his skin for several months. His most recent use of amphetamines was almost one month before this presentation. He believed the crawling sensation was caused by a ‘hexapod’ beneath his skin, and tried to dig them out with his fingernails and fingernail tools. New and resolving scattered excoriations on his elbows, face, waist, and legs were noted (Figure 1). A skin biopsy revealed chronic excoriated dermatitis with secondary fungal infection, but no evidence of an insect (Figure 2). Delusional infestation secondary to amphetamine use was suspected. We prescribed aripiprazole 2.5 mg/day and provided counseling for his amphetamine abuse. One week later, he reported that the itching sensation had decreased by almost 60% along with the frequency of his delusional behavior. His skin lesions also ameliorated under antifungal treatment with terbinafine 250 mg/day. Because of the great improvement of the symptoms, we maintained the treatment dosage of aripiprazole. Three weeks later, his delusion had dissipated and no adverse effects were noted.

Figure 1.

Multiple excoriated skin lesions on the right elbow.

Figure 2.

The spores were highlighted with Gomori’s methenamine silver stain.

Although there are several case reports on amphetamine-related delusional parasitosis (Buscarino et al., 2012), our case is the first of amphetamine-induced delusional infestation treated with aripiprazole. Delusional infestations have also been reported in cases with cocaine, methylphenidate, and pemoline use. The inhibition of dopamine transporters by psychostimulants in the striatum with a corresponding increased dopamine level may be the cause of this condition. Therefore, cessation of the psychostimulants is crucial in the management of substance-related delusional infestations.

Pimozide was broadly used in treating delusional infestation, however, the concerns of QTc interval prolongation limited its use. Atypical antipsychotics such as olanzapine and risperidone have been shown to have a relatively high benefit/risk ratio as first-line agents for delusional infestation (Freudenmann and Lepping, 2009).

Aripiprazole, a dopamine D₂ partial agonist, is approved to treat schizophrenia and bipolar disorder, and can be well-tolerated in long-term use for less adverse effects such as metabolic syndrome or extrapyramidal symptoms. Aripiprazole has been reported to have fair efficacy in treating delusional parasitosis, with dosages ranging from 5 to 30 mg/day and improvements in two to eight weeks (Antoni Bennàssar et al., 2009; Tzeng and Chiang, 2010).

In the current patient with amphetamine abuse and delusional infestation, his psychotic symptoms responded well to a relatively low dose of aripiprazole (2.5 mg/day). However, the exact pharmacological mechanism involved in delusional infestation secondary to drug abuse needs further studies to confirm the optimal dose and treatment duration.