A 22-year-old patient taking Benadryl for sleep complains of difficulty with waking up in the morning. What is the most likely cause of this complaint?

A. Comorbid sleep disorder: While a coexisting sleep disorder could contribute to morning grogginess, the patient’s use of diphenhydramine (Benadryl) and timing suggests the complaint is more directly related to the medication rather than an underlying sleep disorder. B. Loss of sleep maintenance: Diphenhydramine primarily promotes sleep onset rather than maintenance. Difficulty staying asleep is not typically the cause of morning drowsiness in this scenario. C. Next-day hangover effects: Diphenhydramine is an antihistamine with sedative properties. Its residual effects can persist into the next day, causing grogginess, sluggishness, and difficulty waking—commonly referred to as “next-day hangover” or residual sedation. D. Drug toxicity: Therapeutic doses of diphenhydramine rarely cause toxicity in otherwise healthy adults. Persistent morning sleepiness is more likely a normal pharmacologic effect than toxic accumulation.