Anti-hypertensive drugs vasodilator ( Minoxidil and Hydralazine )
Drugs:
Minoxidil
Hydralazine
Mechanism of action:
Minoxidil and Hydralazine relax the vascular smooth muscle of both arteries and arterioles. However, these drugs do not dilate the veins, which leads to reduced cardiac afterload only.
When relaxing vascular smooth muscle, this reduces peripheral resistance and thus reduces blood pressure.
Hydralazine stimulates the formation of nitric oxide by the vascular endothelium, leading to cGMP- mediated vasodilation and hydralazine also, hydralazine causes hyperpolarization by opening potassium ion channels, potassium exit outside the cell and sodium entry into the cell (the number of potassium ions leaving the cell is much more than the number of sodium ions entering the cell).
Pharmacological action:
These drugs reflex stimulation of the heart, which results in an increase in myocardial contractility, an increase in oxygen demand, and an increase in heart rate, which eventually results in cardiac failure, myocardial infarction, and angina pectoris.
Also, these drugs increase renin concentration, which leads to increased water and sodium retention ( hypervolemia ) .
The uses:
1- Hydralazine: used in pregnancy induced hypertension ( last trimester only )
2- Minoxidil: used to treat male baldness ( topically only )
Side effect:
1- Hydralazine:
Headache
Sweating
Tachycardia
Arrhythmia
Angina
Nausea
Lupus syndrome
2- Minoxidil:
Hypertrichosis