Adrenergic Drugs

Introduction & terminology

• Adrenergic (sympathomimetic) drugs — mimic the actions of adrenaline or of sympathetic stimulation; antiadrenergic / adrenergic antagonist drugs block the receptor actions of catecholamines at α, β or both adrenoceptor classes.
• Three endogenous catecholamines — noradrenaline (NA) — transmitter at most postganglionic sympathetic terminals; adrenaline (Adr) — the adrenal-medullary hormone acting via its circulating concentration; dopamine (DA) — central transmitter (basal ganglia, CTZ) with a limited renal-vascular peripheral role.
• Isoprenaline — synthetic pure β agonist with negligible α action — the pharmacological tool used to define β responses; NA and Adr underpin the "fight-or-flight" response.
• Scope — drugs either mimic catecholamines, block their synthesis / release / reuptake, or antagonise them at adrenoceptors — the framework for this whole topic.