Which of the following is a common side effect of medication?

Dry mouth is a common side effect of a variety of medications, especially those that affect the central nervous system or the autonomic nervous system. It can occur with antihistamines, antidepressants, antipsychotics, and many others. This side effect happens because these medications can inhibit salivary gland function, leading to a reduction in saliva production.

While increased energy, weight gain, and improved vision may indeed be effects of certain medications, they do not have the same prevalence as dry mouth across a range of drug classes. For example, weight gain can be a side effect of some medications, but not all. Likewise, increased energy is more typical of stimulants, and improved vision is not commonly reported among the side effects of medications. Thus, dry mouth is noted as a more universally recognized side effect among patients taking different kinds of medication.