Anticholinergic drugs are frequently used in psychiatry for the prophylaxis and treatment of extrapiramidal symptoms caused by neuroleptics. Abuse of anticholinergic agents has been reported in patients with psychotic disorders, on treatment with neuroleptics, and polysubstance use disorders. We are reporting the case of a patient who presented with hypoactive delirium as a consequence of biperiden dependence. The clinician must pay special attention to detect anticholinergic misuse in patients presenting with delirium of unknown cause. 1. Introduction Anticholinergic drugs such as biperiden, benztropine, procyclidine, and trihexyphenidyl are regularly used in clinical practice for the prophylaxis and treatment of extrapiramidal side effects associated with neuroleptics as well as for tremors in Parkinson’s disease [1]. Although thought to be rare, anticholinergic misuse has been reported in several clinical settings. Its abuse potential could be related to its inhibiting action on neuroleptic-induced anhedonia [2–4]. Also, several cases of polysubstance abuse including biperiden have been reported [5, 6]. The neurotransmitter acetylcholine is thought to play a major role in the pathogenesis of delirium. This was first proposed when electroencephalographic changes compatible with delirium were found after the administration of anticholinergic substances and reversal with cholinergic agents. Anticholinergic delirium may present with altered mental status, waxing and waning level of consciousness, urinary retention, attention and concentration deficits, dry mouth, cardiac arrhythmia, blurred vision, hypothermia, fever, hot skin, and decreased convulsive threshold [1, 7, 8]. We are reporting a case of a patient who came to the addiction unit for treatment of biperiden dependence. He initially presented hypoactive delirium associated to his anticholinergic use. 2. Case Report This is a 47-year-old-man that was referred to the addiction unit of Hospital de Virgen de La Arrixaca in Murcia, Spain for the treatment of anticholinergic drug abuse. Patient reported self-medicating with biperiden and developing tolerance to this drug. He described this effect as feeling relaxed and sociable. Given his multiple unsuccessful attempts to quit biperiden, the patient thought that he was addicted to this drug and wanted to be treated for it. Past psychiatric history was significant for a 31-year history of alcohol and marijuana abuse and a 22-year history of cocaine abuse. At the time of presentation, he had been abstinent from alcohol or other drugs for two years.
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