A nurse is preparing to administer a newly prescribed medication to a client who has rosacea and a history of hypertension. Which of the following medications requires frequent blood pressure monitoring?

Brimonidine topical gel is an alpha-2 adrenergic agonist used to treat the facial redness associated with rosacea. Although it is applied topically, systemic absorption can occur, and because alpha-2 agonists reduce sympathetic outflow, they can lower blood pressure. In a client who already has a history of hypertension and may be taking antihypertensive medications, this systemic effect creates a clinically significant risk of additive hypotension. Frequent blood pressure monitoring is therefore necessary when this agent is used in such a patient. Oral isotretinoin is associated with hyperlipidemia and teratogenicity rather than blood pressure changes. Oral doxycycline is a tetracycline antibiotic used for inflammatory rosacea; its main concerns include photosensitivity and gastrointestinal upset, not blood pressure effects. Metronidazole topical gel is a first-line treatment for rosacea papules and pustules; its topical application results in negligible systemic absorption, and it carries no meaningful cardiovascular risk. Among the choices, only brimonidine directly involves adrenergic receptor activity that could affect systemic vascular tone and blood pressure, making it the agent requiring careful blood pressure monitoring in this hypertensive client.