DIPHENDHYDRAMINE ABUSE AND WITHDRAWAL IN A PATIENT WITH A HISTORY OF A 2.5 GRAM/DAY DEPENDENCY

Background: While excessive use of anticholingeric agents has been widely documented among individuals taking neuroleptic agents, cases of diphenhydramine (DPH) abuse and withdrawal are seldom reported. Case Report: A 38year-old female with a history of depression presents to the ED with confusion and refusal to take her medications--olanzapine, gabapentin, mirtazapine, clonazepam. In addition, the patient has a history of escalating DPH use over the past 18 months, secondary to its 'relaxing' effect, reaching a maximum of 100 25 mg tabs qd (2.5 gm) for a 10 month period of time and gradually tapering to 1.25 gm qd over the past 4 wks. She had not taken any of her medications including DPH over the 2 days prior to presentation. During the past 18 months she had not complained of dry mouth, urinary retention, constipation, confusion, sedation, or blurry vision. ED vital signs were T 36.1, P 109, BP 121/75, and R 16. She was calm with a normal exam except for disorientation and confusion. Her CBC and serum chemistries were normal. She was admitted to the hospital for observation of worsening withdrawal symptoms. By day 2 her mental status was clear but she complained of anorexia, nausea, and increased anxiety followed on day 3 by diarrhea, abdominal cramping and episodes of flushing. She was treated only with clonazepam, maintaining normal vitals. All somatic complaints gradually resolved, but she continued to complain of anxiety prior to discharge to outpatient drug rehabilitation on day 6. A DPH level drawn upon initial presentation (48 h after last DPH dose) was 550 ng/mL (ref. avg peak serum DPH level 2h after a single 50 mg oral dose is 66 ng/mL.) Conclusion: This is a case of presumed DPH withdrawal presenting with mild confusion, anxiety and somatic symptoms of mild cholinergic excess without alteration in vital signs and demonstrating a self-limiting course. A remarkable tolerance to DPH characterized this case.
Shiuh T, Wax P. Department of Emergency Medicine, University of Rochester Medical Center, Rochester, [...]