Adrenergic Pharmacology

Adrenergic Receptors

Receptor	Binding Affinity	Effects	Mechanism	Agonists	Antagonists
α1	NE > Epi >> Iso	Smooth muscle contraction, ↑SVR, ↑MAP Mydriasis, urethral sphincter contraction	Gq → PLC → IP3/DAG → [Ca2+]i	NE Phenylephrine (pure α1) Midodrine	α1 selective: Prazosin Tamsulosin
α2	Epi = NE >> Iso	↑SVR, ↑MAP Decreased insulin release, inhibits lipolysis, decreases aqueous humor production	presynaptic Gi → ↓AC → ↓cAMP → inhibition of NT release, sympatholytic effects	Dexmedetomidine Clonidine	Non-selective: Phenoxybenzamine Phentolamine Trazodone
β1	Iso > NE > Epi	↑Chronotropy (myocytes), ↑Inotropy (SA node) →↑CO ↑Renin release/↑volume (JGA) Amylase secretion	Gs → ↑AC → ↑cAMP	Dobutamine Isoprenaline Norepi	Cardiac Selective: Metoprolol Atenolol Esmolol
β2	Iso > Epi > NE	Smooth muscle relaxation	Gs, cAMP up	Albuterol Formoterol Isoprenaline Salmeterol Terbutaline Ritodrine	Non-Selective: Propranolol Nadolol Pindolol Timolol Carvedilol (anti-α1) Labetalol (anti-α1)
β3	Iso > Epi = NE	Lipolysis, bladder detrusor relaxation	Gs, cAMP up	Mirabegron	SR 59230A