Q. How do blood pressure drugs work? And how will my doctor know which one is right for me?
A. There are many different drugs for blood pressure and they work in different ways. Finding which one will work best for you may involve a process of trial-and-error. But in the end, you'll be rewarded with a medication that offers the best blood pressure control with the fewest side effects.
If you have other health conditions -- diabetes and heart disease often accompany hypertension, for instance -- certain drugs can lower blood pressure while also helping to treat these conditions.
I'll briefly summarize the different classes of blood pressure drugs and how they work. I won't go into the potential side effects of these drugs here, but you should discuss them with your doctor. (On my website, AskDoctorK.com, I've put tables with examples of the different types of drugs.)
• Diuretics, or "water pills," help the kidneys eliminate sodium and water from the body. This decreases blood volume, so the heart has less to pump with each beat. Of all the blood pressure drugs used today, diuretics have been around the longest and their beneficial effects are solidly proven.
• ACE inhibitors decrease blood volume by preventing the kidneys from retaining sodium and water. They do this by deactivating angiotensin-converting enzyme (ACE). ACE is a natural chemical (an enzyme) that converts another natural chemical, angiotensin I, to the chemical called angiotensin II. Angiotensin I is inactive, but angiotensin II raises blood pressure. So reducing the amount of angiotensin II by reducing ACE, the enzyme that makes angiotensin II, helps lower blood pressure.
• Angiotensin-receptor blockers (ARBs) block the blood pressure-raising effects of angiotensin II. So, the ACE inhibitors reduce the amount of angiotensin II the body makes, and the ARBs reduce the blood pressure-raising effect of angiotensin II.
• Calcium-channel blockers slow the movement of calcium into the smooth-muscle cells that are in the heart and the walls of the blood vessels. This makes heart muscle pump less forcefully (but still forcefully enough), which reduces blood pressure. Calcium-channel blockers also relax the muscle in the blood vessel walls, which makes blood vessels open wider, lowering blood pressure.
• Anti-adrenergics limit the action of the hormones epinephrine and norepinephrine. This relaxes the blood vessels and reduces the speed and force of the heart's contractions.
• Direct-acting vasodilators relax the arteries. They act quickly and are often used in emergencies.
• Direct renin inhibitors inhibit the activity of renin, the enzyme largely responsible for angiotensin II levels. Aliskiren (Tekturna) is a renin inhibitor.
There really is no "best" blood pressure medication. The goal is to find the right medication for you. Often, more than one type of medicine used in combination proves the best. That means finding the medicine or medicine combo that effectively lowers your blood pressure while not causing side effects -- and not costing more than you can afford.
• Dr. Komaroff is a physician and professor at Harvard Medical School. Send questions to AskDoctorK.com.