Which adverse effect can diphenhydramine hydrochloride have on the patient? gastrointestinal system? Nausea Diarthea Anorexia Constipation

Diphenhydramine hydrochloride, a first-generation antihistamine, exhibits several anticholinergic (antimuscarinic) effects. These effects can impact various body systems, including the gastrointestinal (GI) system. **Common GI Adverse Effects of Diphenhydramine:** 1. **Constipation:** This is one of the most commonly reported GI side effects due to the antimuscarinic action, which decreases intestinal motility. 2. **Dry Mouth:** While not directly a GI effect, reduced saliva production can contribute to discomfort in the mouth and throat. 3. **Nausea:** Some patients may experience mild nausea, although it's less common compared to constipation. **Less Common or Unrelated Effects:** - **Diarrhea:** Generally, diphenhydramine is more likely to cause constipation rather than diarrhea due to its anticholinergic properties. - **Anorexia:** While a decreased appetite can occur, it's not as consistently associated with diphenhydramine as constipation is. **Conclusion:** Among the listed options—nausea, diarrhea, anorexia, and constipation—**constipation** is the most directly associated gastrointestinal adverse effect of diphenhydramine hydrochloride. **Answer:** Constipation is a gastrointestinal adverse effect that diphenhydramine hydrochloride can cause.