6.12: Adrenergic Antagonists: Pharmacological Actions of ɑ-Receptor Blockers
α-Adrenergic antagonists, known as α-blockers, exert their effects by inhibiting α-adrenoceptors, leading to specific physiological actions. α1-blockers and α2-blockers have distinct pharmacological actions and therapeutic applications.
α1-blockers: These drugs inhibit α1-adrenoceptors on smooth muscle cells, resulting in vasodilation. This vasodilation lowers blood pressure, making α1-blockers valuable in treating hypertension. Additionally, α1-blockers effectively address urinary obstruction caused by benign prostatic hyperplasia (BPH). These drugs reduce urine flow resistance and alleviate BPH-related symptoms by relaxing smooth muscles in the prostate and bladder neck.
α2-blockers: These antagonists act on presynaptic α2-adrenoceptors, increasing sympathetic neurotransmitters' release. This promotes adrenoceptor activation in target organs. However, non-selective α-blockers interacting with both α1 and α2 receptors are generally not used for hypertension management due to their severe side effects.
Overall, adrenergic antagonists, particularly α1-blockers, play a crucial role in modulating the sympathetic nervous system and offer therapeutic benefits for conditions such as hypertension and urinary obstruction associated with BPH.
