A nurse is collecting data from a client who is taking dimenhydrinate to treat motion sickness. Which of the following findings is an adverse effect of this medication?

A. Drowsiness. Dimenhydrinate is an antihistamine that works by blocking histamine and acetylcholine receptors in the brain to prevent nausea and vomiting. A common adverse effect is drowsiness due to its sedative properties, which can impair alertness and coordination. Clients should be advised to avoid activities requiring mental alertness, such as driving, until they understand how the medication affects them. B. Hypertension. Dimenhydrinate does not typically cause hypertension. Instead, it may lead to mild hypotension due to its sedative and anticholinergic effects. Clients with pre-existing hypertension should still monitor their blood pressure, but significant increases are uncommon. C. Polyuria. Increased urination is not associated with dimenhydrinate use. Antihistamines, including dimenhydrinate, have anticholinergic properties, which can lead to urinary retention rather than increased urine output. Clients experiencing difficulty urinating should report this to their healthcare provider. D. Dependent edema. Dimenhydrinate does not cause fluid retention or edema. Medications that contribute to edema typically involve hormonal, cardiovascular, or kidney-related effects, which are not mechanisms of dimenhydrinate. If a client develops unexplained edema, other underlying conditions should be investigated.