11.6: Antianginal Drugs: Nitrates and β-Blockers
In cardiovascular health, antianginal drugs combat angina pectoris — a condition marked by chest pain owing to diminished blood flow to the heart.
Organic nitrates, such as nitroglycerin, play a pivotal role. Once metabolized, they liberate nitric oxide, a molecular marvel. Nitric oxide triggers guanylyl cyclase and augments cGMP production. This biochemical cascade orchestrates the relaxation of vascular smooth muscles, ushering in vasodilation and enhancing coronary blood flow. Administered sublingually for swift action, nitroglycerin's potency comes with side effects such as headaches, postural hypotension, and facial flushing, a testament to its biochemical prowess.
In the grand symphony of cardiovascular regulation, β-blockers, represented by stalwarts like atenolol and metoprolol, take center stage. With precision, they intercept adrenaline and noradrenaline at β1-adrenergic receptors in vascular and cardiac muscle cells. Their mastery lies in reducing myocardial oxygen demand. They achieve this by tempering the heart rate, myocardial contraction force, and systemic blood pressure. Orally administered, these agents initiate their effects within an hour, albeit not without trade-offs; side effects include fatigue, cold extremities, hypotension, and bradycardia.
Within the complex physiological networks of the human body, antianginal medications function according to sophisticated biochemical pathways. Agents such as nitric oxide and β-blockers act as critical regulators, directing vasodilation and modulating the impacts of adrenaline. Despite the manifestation of side effects, the relief these medications provide to hearts afflicted by angina underscores their indispensable role in cardiovascular therapeutics.
