These potent drugs are used to treat resistant and difficult cases of high blood pressure which do not respond well to other drugs. They work on muscles (directly) in the wall of the arteries preventing the muscles from constricting the arterial wall. The important direct vasodilators are:
- Hydralazine (Nepresol)
- Minoxidil (Mintop)
Side Effects and Cautions
Common side effects of direct vasodilators include a fast heart beat and water retention, neither of which is desirable if we have high blood pressure. This is the reason the physicians prescribe direct vasodilator with a beta blocker and a diuretic which can reduce these symptoms. Other side effects of direct vasodilators are:
- Excessive hair growth on the body
- Nasal congestion
- Gastro intestinal problems
- Swelling of gums. Hydralazine taken in large doses can increase the risk for ‘Lupus’ -a connective tissue disease.
If the blood pressure of a person reaches a dangerously high level it may be necessary to reduce it rapidly to avoid serious damage to organs and even death. Examples of these situations are:
- Heart attack
- Heart failure
- Sudden blindness
- Rupture in the wall of aorta
During blood pressure emergencies, doctors inject high blood pressure medications into the veins of the patient. The goal is to lower the blood pressure by 25 percent within several minutes to two hours. Reducing the blood pressure too fast can cause other serious, even fatal condition. Once the blood pressure is reduced 25 percent then the goal is to lower the blood pressure to near 160/100 mm Hg within 6 hours.
The types of injectable medications used in hypertensive emergencies include:
- Vasodilators such as fenoldopam, nicardipine hydrochloride, nitroglycerin and sodium nitroprusside
- Alpha and beta blockers such as esmolol hydrochloride, labetalol hydrochloride, phentolamine.