Alfablokaate

Alfablokaate refers to pharmacological blockade of alpha-adrenergic receptors, principally the alpha-1 and alpha-2 subtypes, which reduces sympathetic vasoconstrictor tone. Blocking these receptors leads to vasodilation of arterial and venous vessels and, consequently, can lower blood pressure. The effects depend on the selectivity and reversibility of the agent used.

There are two broad classes of alfablokaate drugs. Nonselective agents block both alpha-1 and alpha-2 receptors and may produce more widespread effects; examples include phenoxybenzamine (an irreversible agent) and phentolamine (reversible). Selective alpha-1 blockers, such as prazosin, doxazosin, terazosin, and tamsulosin, primarily reduce vascular resistance with varying degrees of impact on blood pressure and are used for different clinical indications. Alpha-1A–selective agents like tamsulosin are particularly used to treat lower urinary tract symptoms due to benign prostatic hyperplasia with comparatively fewer effects on blood pressure.

Medical uses of alfablokaate include preoperative management of pheochromocytoma to prevent hypertensive crises, treatment of certain hypertensive conditions, and, with specific drugs, relief of lower urinary tract symptoms due to benign prostatic hyperplasia. Some agents have been used off-label for conditions such as Raynaud phenomenon or anxiety-related sympathetic overactivity, though this varies by drug and clinical setting.

Administration and pharmacokinetics vary by compound. Phenoxybenzamine is long-acting and acts irreversibly, while phentolamine is shorter acting and reversible. Alpha-1 blockers are usually given orally, with dosing titrated to blood pressure and symptom relief; side effects commonly include orthostatic hypotension, dizziness, nasal congestion, and, in some cases, edema or reflex tachycardia. Careful monitoring is advised during initiation and dose adjustments.