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Clinical pharmacy 2024/2025 Level 3 Pharm D Pharmacology 1 (PO 502)

10- Direct Vasodilators (direct-acting smooth muscle relaxants)

hydralazine and Minoxidil
➢ producing relaxation of vascular smooth muscle ➔ ↓resistance
➔↓blood pressure.
MOA ➢ Activation of the potassium channels ➔ ↑ potassium efflux ➔

hyperpolarization of the smooth muscle membrane. ➔calcium influx
is inhibited ➔ arteriolar smooth muscle relaxes.

not been used as primary drugs to treat hypertension (last choice) ➔
Last choice
due to reflex heart stimulation

1. reflex stimulation of the heart ➔ resulting in the competing reflexes

of increased myocardial contractility, heart rate, and oxygen
consumption.
S/E 2. prompt angina pectoris, myocardial infarction, or cardiac failure in

predispose individuals.
3. ↑ plasma renin concentration ➔ sodium and water retention
 all blocked by concomitant use of a diuretic and a β-blocker.

Hydralazine Minoxidil

causes dilation of resistance
Action direct vasodilation, acting primarily on arteries vessels (arterioles) but not of
and arterioles (decrease after load). capacitance vessels (venules).

1) used to treat moderately severe hypertension
 in combination with a β-blocker, (to balance ➢ orally for treatment of sever
the reflex tachycardia) and a diuretic (to to malignant hypertension
decrease sodium retention). that is refractory to other

 Together, the three drugs ➔ ↓ cardiac drugs.

Use output, plasma volume, and peripheral ➢ causes hypertrichosis (the
vascular resistance growth of the body hair) ➔
2) Hydralazine Monotherapy➔ used topically (sprays) to
controlling blood pressure in pregnancy- treat male pattern

induced hypertension (after methyl dopa), baldness.
but recent it's C.I as it affects circulation of

Infant as well as mother
➢ headache, tachycardia, nausea, sweating, ➢ serious sodium and water
arrhythmia, and precipitating of angina. retention ➔ volume
S/E ➢ A lupus-like syndrome can occur with high overload, [edema, and

dosage, but it is reversible on congestive heart failure]
discontinuation of the drug. ➢ hypertrichosis

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