Objective: Delusional parasitosis is a psychiatric disorder characterized by the belief of being infested with parasites, insects or bugs against medical evidence that an actual infestation is present. Patients may even report tactile hallucinations known as formication, which is a physical sensation resembling a pin-pricking or tingling feeling that is most often described as insects crawling on or burrowing under the skin. Delusional parasitosis may be primary or secondary in nature. Secondary organic delusional parasitosis occurs when a medical illness or substance use causes the symptoms. Any illness or medication for which formication is a symptom or side effect can become a trigger or underlying cause of delusional parasitosis. Drug use can sometimes cause formication, and thus delusional parasitosis. Specifically, we believe there may be a pharmacological correlation between certain drugs and delusional parasitosis. Patients taking the anti-Parkinson’s drug, pramipexole, or using amphetamines seemed to have higher rates of delusional parasitosis as seen in a clinic setting. We sought to compare this patient group with the normal population to see if there was any increase in causation.
Methods: 341 patient files were examined using the UCLA Epic database system and were compared to a control group of 100 patients. Patients were examined on the basis of neurodermatitis-related skin diagnoses, which included one more or the following: formication, skin sensation disturbance, allodynia, dysesthesia, paresthesia, hyperesthesia, skin pain, burning, sensation, numbness or tingling, atopic neurodermatisis, or sensitive skin. Patients were cross-examined to look for pramipexole or amphetamine use concurrent with their neurodermatitis condition. Patients with positive history of amphetamine, pramipexole, and phentermine use were analyzed by demographics, including age and gender. Patients with positive history of medication use were analyzed to assess correlation between medication type and history of delusions of parasitosis and neurodermatologic disorders. Control data was then used to compare medication history.
Results: Out of 341 patients presenting with neuroderamatitis, 5 had also taken pramipexole anywhere from 1 month duration to 4 years duration. 17 of the 341, or 5%, were on at least one type of amphetamine. There were 10 females with positive medication history in comparison to 7 males, though they were roughly evenly split between pramipexole use with 3 female and 2 male patients having positive pramipexole history. In regards to comparison by age, the majority of patients with positive medication history were between 45 and 65 years of age (15 patients), with the majority having a positive amphetamine history. Patients were compared to a control dataset of 100 patients.
Conclusion: Delusions of parasitosis are a group of conditions that have been linked to specific medications, including methamphetamines and other associated medications. There is an association between neurodermatologic conditions such as delusions of parasitosis and history of pramipexole and amphetamines. A thorough clinical history, including medication history, is thus warranted in order to rule out suspected medication-associated delusional parasitosis in patients presenting for dermatologic evaluation.