Final answer:
The drug contraindicated in a patient with primary open-angle glaucoma and asthma is β blockers due to their potential to increase intraocular pressure and induce bronchoconstriction. Alternative treatments include leukotriene receptor antagonists for asthma and acetazolamide for glaucoma.
Step-by-step explanation:
The drug contraindicated in a patient with primary open-angle glaucoma (POAG) and asthma is β blockers. These are known to potentially worsen both conditions.
β blockers can decrease aqueous humor production in the eye, potentially increasing intraocular pressure, which is harmful for glaucoma patients. In asthma, β blockers can lead to bronchoconstriction by blocking the β-receptors in the bronchioles which are responsible for maintaining airway patency. This can worsen asthma symptoms or precipitate an asthma attack. Alternative treatments should be considered for patients with this combination of conditions, such as leukotriene receptor antagonists for asthma, which do not carry the same risks for glaucoma patients.
For primary open-angle glaucoma, acetazolamide is a treatment option. It competitively inhibits carbonic anhydrase, which helps reduce intraocular pressure by reducing aqueous humor formation. In contrast, for asthma management, medications like sympathomimetic drugs can be useful as they dilate the airways and help clear mucus from the respiratory tract.