What should be monitored for patients taking diphenhydramine?

Monitoring for urinary retention in patients taking diphenhydramine is essential, as this medication is an anticholinergic agent. Anticholinergic drugs can interfere with the normal function of the bladder, leading to difficulty in urination or urinary retention. This side effect is particularly significant in elderly patients or those with pre-existing urinary conditions, as they may be more susceptible to such complications.

In contrast, while it is important to monitor for weight changes and skin rashes in some medication contexts, these are not primary concerns with diphenhydramine. Blood pressure fluctuations may also be relevant in certain populations, but they are not typically associated with diphenhydramine use. Therefore, urinary retention stands out as a key monitoring consideration due to the medication's pharmacological effects.