Diphenhydramine constipation with

With long-term use, the most problematic side effect is weight gain. However, many antihistamines including diphenhydramine also possess potent anticholinergic effects. This can cause dry mouth, blurred vision, constipation, confusion, and urinary retention. Because anticholinergic effects are especially problematic for the elderly, we advise against the routine use of antihistamines to treat elderly patients with insomnia. 

Answer B. Docusate is a stool-softening laxative that facilitates mixing of oil and water via its surfactant properties. Drugs that have muscarinic blocking effects, like scopolamine and the antihistamines diphenhydramine and promethazine, tend to cause constipation by decreasing GI motility. Loperamide is an opioid derivative, with no analgesic activity, used in the treatment of diarrheal states. 

Common adverse events sedation, respiratory depression, pruritus, nausea/vomiting, constipation, and urinary retention, which are treated with a naloxone 40-80 pg IV bolus followed by an infusion of 50-100 pg/h. However, these adverse events are relatively less commonly observed with epidural hydromorphone than with neuraxial morphine regimens. Pruritus is treated with a naloxone infusion of 50-100 pg/h, diphenhydramine 12.5-50 mg or propofol infusion of 10 mg/h. Nausea and vomiting is best treated with either ondansetron (4-8 mg IV), low-dose droperidol (0.625-1.25 mg IV), metoclopramide (10 mg IV every 4-6 h), or transdermal scopolamine patch during the first 10 hours following administration. 

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