What is a potential side effect of cimetidine that the nurse should monitor for?

Cimetidine is a histamine H2 receptor antagonist primarily used to reduce gastric acid secretion, and one of its notable side effects is gynecomastia, which is the development of breast tissue in males. This effect is associated with cimetidine's potential to inhibit androgen and increase prolactin levels, leading to hormonal imbalances that can cause breast tissue growth. Monitoring for gynecomastia is important because it can indicate how the medication is affecting hormonal levels in patients, particularly in long-term use.

Other side effects of cimetidine and aspects like insomnia, hyperactivity, and constipation can occur but are less commonly associated with this medication compared to gynecomastia. The unique effect on breast tissue growth makes gynecomastia a key side effect that nurses should be vigilant about when administering cimetidine.