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.