The American Heart Association explains several doctor-prescribed classes of medications can lower blood pressure fast, including combination alpha and beta-blockers, vasodilators, central agonists and ACE inhibitors. Combined alpha and beta-blockers may be prescribed as intravenous medications during a hypertensive crisis to lower blood pressure immediately if a patient is in danger of heart failure.
Vasodilators cause the muscles in blood vessel walls to dilate, or open up, to allow better blood flow. One such drug is minoxidil, a medication used in severe high blood pressure cases. Minoxidil may cause fluid retention and hair growth, according to the AHA.
ACE inhibitors prevent the body from producing the hormone angiotensin, which allows blood vessels to widen. Mayo Clinic indicates ACE inhibitors are used for stage 1 high blood pressure with more than 140/90 millimeters of mercury, and these types of drugs are for stage 2 high blood pressure with more than 160/100 millimeters of mercury. Patients with stage 2 high blood pressure usually take two different medications to try to lower blood pressure readings. People with resistant high blood pressure may be prescribed three or four medications to try to bring high blood pressure under control.
WebMD explains doctors may treat extreme cases of hypertensive emergencies with intravenous medications to prevent organ damage. Doctors prescribe a separate treatment regimen for organ damage after blood pressure is lowered.