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Central
alpha2-agonist: Clonidine
(Catapres), methyldopa (Aldomet), Guanabenz actate, and Guanfacine
hydrochloride. These drugs
stimulate the central alpha2 receptors in the brain and block part of the sympathetic
stimulus to the brain which results in a decreased blood pressure and heart
rate. -Clonidine
is indicated for the treatment of hypertensive urgencies and hypertension that
is poorly controlled with other
agents. It can produce bradycardia
and is associated with a rebound hypertension when it is abruptly discontinued.
Clonidine can be given in a patch form to treat hypertensive patients who
are not to eat or drink orally and/or for patients who may have dementia and
refused to take oral medications. -Methyldopa
is recommended for females with hypertension that is first diagnosed in
pregnancy. It can produce
autoimmune and/or liver disorders. Centrally
acting antihypertensive: Reserpine -Reserpine
acts by decreasing central and peripheral catecholamines which decreases
sympathetic nerve activity. The
decreased sympathetic nerve
activity produces sedation, vasodilation, and a decreased heart rate.
Reserpine is an older drug and is not commonly used to treat
hypertension. Alpha-blockers: Prazosin (Minipress), Terazosin (Hytrin), and doxazosin (Cardura).
Studies have suggested that alpha-blockers may increase HDL and mildly decrease
cholesterol. These agents are used
in the treatment of BPH (benign prostatic hypertrophy) and are associated with
postural hypotension and syncope especially after the first dose.
It is recommended that initial dose of these agents be given right before
bedtime to decrease the risk of syncope. In
addition, alpha-blockers should be
initiated using the lowest recommended starting dose and the dose should be
slowly increased if needed. These
antihypertensive medications should be restarted at the lowest recommended
starting dose if it is discontinued for more than a few days.
Direct
vasodilators:
Minoxidil (Loniten); hydralazine (Apresoline).
-Minoxidil
is given orally for the treatment of severe hypertension and topically for the
treatment of male pattern baldness. It
is usually given with a beta-blocker (to treat tachycardia secondary to the
drug) and a diuretic for treatment of edema induced by minoxidil.
It is associated with pericardial effusions, hypertrichosis, and may
exacerbate angina. Minoxidil is
contraindicated in patients with pheochromocytoma.
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