Drug-Induced Tactile Hallucinations Beyond Recreational Drugs

In monosymptomatic hypochondriacal psychosis (MHP), such as delusional infestation (DI), the patient has a fixed, false, encapsulated belief associated with tactile hallucinations (TH), most commonly formication, which is defined as cutaneous sensations of crawling, stinging, biting, etc., without evidence of infestation. Drug-induced TH should be considered in patients with suspected MHP. Although recreational drugs such as cocaine, amphetamines, and narcotics are well known to induce TH, many busy practicing dermatologists may not be familiar with other types of medications that can induce TH. A literature search for peer-reviewed articles was conducted in the PubMed, PsychInfo, Cochrane, and Embase databases. For each article, the medication(s) that induced TH was identified in a systematic way. The most commonly reported group of medications to induce TH was anti-Parkisonian agents, followed by antidepressants, prescription stimulants, antihypertensives (propranolol), and antiepileptics. In many cases, other types of hallucinations, such as visual and auditory, were present. Patients also commonly presented with psychiatric comorbidities. Although the conclusions that can be derived from this literature review are limited, it appears that certain medications that alter neurotransmitters, especially dopamine and, less convincingly, norepinephrine and serotonin, can be associated with TH. Drug-induced TH should also be considered in patients presenting with multiple types of hallucinations and patients with existing psychiatric comorbidity. Drug-induced TH, especially with an underlying psychiatric diagnosis that is separate from MHP, may be a more manageable disease entity compared with bona fide MHP.