Final answer:
Propranolol is a beta-blocker that manages hypertension by decreasing heart rate and cardiac output, which ultimately lowers blood pressure. It blocks beta-adrenergic receptors, reducing the effects of adrenaline and causing vasodilation. Overuse can lead to serious side effects, so it must be prescribed carefully.
Step-by-step explanation:
Propranolol (Inderal), a beta-blocker, controls hypertension by blocking adrenergic receptors, primarily beta-1 receptors, which are responsible for the effects of adrenaline on the heart. This action leads to a decrease in heart rate and cardiac output, resulting in lower blood pressure. Beta-blockers like propranolol also inhibit the release of renin, which is part of the renin-angiotensin system that regulates blood pressure and fluid balance. As a result, patients experience both a reduction in heart rate and vascular resistance, contributing to the overall antihypertensive effect.
Adrenaline typically has a stimulatory effect on the heart, increasing both rate and force of contractions, which raises blood pressure. By blocking the receptors that adrenaline would normally activate, propranolol decreases the heart's workload and oxygen demand. This mechanism also helps in the treatment of conditions like angina and following a myocardial infarction. However, caution is advised since overprescription of beta-blockers can lead to side effects such as bradycardia and in extreme cases, cardiac arrest.
There are also non-cardiac effects of propranolol, including causing blood vessels to dilate due to its blockade of beta receptors associated with vasoconstriction. Sympatholytic drugs, which include alpha-blockers as well, function by a similar mechanism and affect the sympathetic nervous system to lower blood pressure.