A client is newly prescribed a medication that will block the effects of histamine for the treatment of a mental health disorder. The client asks, “What side effects should I anticipate with this new medication?” Which response by the nurse is accurate?

Choice A reason: Histamine blockade, as in antipsychotics like olanzapine, promotes sedation, not weight loss. Weight gain is common due to histamine’s role in appetite regulation via hypothalamic signaling. Weight loss is not a typical side effect, making this response inaccurate for histamine-blocking medications. Choice B reason: Histamine receptor blockade, common in medications like quetiapine, reduces wakefulness by inhibiting histamine’s alerting effects in the cortex. This causes drowsiness, a frequent side effect in psychiatric treatments, aligning with the pharmacological mechanism and making this the correct response. Choice C reason: Insomnia is not typical with histamine blockade, which promotes sedation. Histamine enhances alertness; blocking it, as in antihistaminic antipsychotics, induces sleepiness, not wakefulness. This response contradicts the neuropharmacological effect, making it incorrect for expected side effects. Choice D reason: Blood pressure increase is unrelated to histamine blockade. Histamine affects wakefulness and appetite, not vascular tone directly. Antihistaminic drugs may cause orthostatic hypotension via other receptors, not hypertension, making this response inaccurate for histamine-blocking medication effects.