• alpha vs. beta
• alpha: 1A, B, D, 2A, B, C
• beta: 1, 2, 3
• endogenous agonists: epi, norepi
• epi likes beta, norepi likes alpha

• nonselective alpha receptor blocker
• reversible
• causes vasodilation, drops BP
• control of hypertensive emergencies, esp due to pharochromocytoma (tumor of adrenals that releases catecholamines, avoid beta blockers, which will increase bp)
• useful in treatment of cocaine-induced [cocaine causes vasoconstriction] hyptertension, where you need to avoid beta blockers and CaCB don't work

• alpha blockers used for bph, treat hypertension
• alpha 1 receptor induces contriction of smooth muscle (release Ca), beta 2 induces dilation
• alpha blockers can increase HR
• alpha 1A blockers are uroselective
• doxazosin, terazosin, alfuzosin, tamsulosin
• titration required for doxazosin, terazosin
• = increase dose slowly to increase in plasma, prevent hypotensive episode
• tamsulosin: titration is dose dependent

non-uroselective alpha1 blocker

quinazoline derivative

functionally uroselective

quinazoline derivative

selective alpha1A blocker (uroselective)

1:40::1B:1A

urinary excretion, others mainly hepatic

instant release t1/2: 4 h

ER: 15 h

alpha a1 blocker with high uroselectivity

no orthostatic hypotension (low dose)

inhibits ejaculation but not orgasm

causes retrograde ejaculation

• agonists
• central alpha 2 receptor = brain, coexpressed with imidazoline-1 receptor
• alpha-methyl-dopa (clean alpha 2)
• dexmedetomidine (clean alpha 2)
• -m/nidine
• clonidine, rilmenidine, moxonidine all have I-1 agonism
• different clinical uses

alpha 2: analgesia and sedation (ADR parotid pain and dry mouth)

imidazol: lower bp (ADR bradycardia, constipation, water retention)

sedative anxiolytic w/o respiratory depression

not used for sedation since lowers bp too much

sedation

dry mouth

bradycardia

orthostatic hypotension

impotence

constipation, nausea

fluid retention

clinical use: hypotension, mydriatic, nasal decongestant

oxymetazoline: nasal decongestant, immediate effect, tolerance :(

phenylephrine: nasal decongestant, IV prep to increase bp