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What are the two orally available arterial vasodilators?

Minoxidil and Hydralazine


What are orally available arterial vasodilators used for?

Long term treatment of HTN.


Explain the MOA of hydralazine.

Vasodilation through generation of nitric oxide which activates guanylate cyclase and produces and increase in cGMP which manifests as a direct relaxant effect on vascular smooth muscle.


What is the dose of hydralazine?

2.5 to 10mg IV


What is the peak and duration of hydralazine?

Peak is 10-20minutes and can last up to 6 hours.


Pharmacokinetically what is important to remember about hydralazine?

It has an extensive hepatic first pass effect.
Onset is 15 minutes
Elimination half time is 3 hours.
After IV less than 15% appears unchanged in the urine.


Name some effects of hydralazine

Reflexive tachycardia (baroreceptor)
DBP is reduced more than SBP
Decreased SVR
Increase CO, SV, CO
People can develop a tolerance and tachyphylaxis
Sodium and H20 retention
Angina with EKG changes?


Clinically when is hydralazine used?

In combination with a BB and diuretic (which limits the increased SNS activity)


What is the effect of minoxidil?

Directly relaxes the arteriolar smooth muscle with little effect on venous capacitance. Orally active.


Clinically when is minoxidil used?

To treat the most severe forms of HTN due to renovascular disease, renal failure, transplant rejection. and used in combination with BB and diuretic (to combat RAAS stimulation and reflexive tachycardia).


What is the specific MOA of minoxidil?

Increases the influx of potassium into vascular smooth muscle resulting in hyperpolarization and vasodilation.


90% of the oral dose of minoxidil is absorbed where?

GI tract.


When do we find peak levels of minoxidil?

1 hour


What is the E1/2T of minoxidil?

2 hours.


How much of the drug do we find unchanged in the urine?



SE of minoxidil?

Marked increase in HR and CO (use a BB to combat this). Increased plasma concentration of NE and renin (use a diuretic). causing Compensatory retention of NA and H20, weight gain, edema, hypertrichosis, pulmonary HTN, pericardial effusion or tamponade.


With minoxidil we can have an abnormal EKG. What is different?

Flat or inverted T wave, increased voltage of the QRS complex.