Dear Dr. Roach: With all the different medications available for high blood pressure, what factors determine the medicine a doctor will prescribe?
The first consideration is whether the person has any other medical conditions that would make a particular medication more advantageous. Someone with diabetes and protein in the urine would benefit greatly from an ACE inhibitor; a person with blockages in the arteries to the heart should be on a beta blocker; someone with migraines might benefit from a calcium channel blocker or beta blocker. When a practitioner can treat two conditions with one medication, it is usually the first choice. Similarly, if there is a condition that would make a particular antihypertensive inappropriate, the clinician avoids prescribing it. Examples include thiazide diuretics in people with gout, and beta blockers in a person with depression.
If there is no particular reason to pick a class of drug based on other medical conditions, the most commonly used classes of blood pressure drugs are diuretics, calcium channel blockers and ACE inhibitors (or their close cousins, angiotensin receptor blockers). A person’s degree of high blood pressure and age are other factors. What is equally important as choosing a blood pressure medicine is to evaluate whether it is effective and to monitor for adverse effects. There is tremendous individual variation in the effectiveness of certain medicines — even race and ethnicity have a small role to play. Further, the initial choice might be based on sound reasons, but if a person can’t tolerate it, it needs to be changed.
Dear Dr. Roach: I am grateful for your recent explanation of statins and beta blockers. Could you also explain what calcium channel blockers do and how they work? I once read they have nothing to do with the mineral calcium. Is that right? Do they interact with statins?
Calcium channel blockers have everything to do with the mineral calcium. Calcium is used as a messenger in the body to turn on and off important cellular functions. Although there are many kinds of calcium receptors, the two kinds that are important for the calcium blockers we use clinically are those in the heart and those in the blood vessels.
In the heart, blocking calcium channels slows the heart rate and decreases the strength of the heart’s contractions. The calcium channel blockers verapamil and diltiazem work predominantly this way. These drugs are useful for people with high blood pressure and some kinds of too-fast heart rhythms.
Blocking calcium channels in the blood vessels opens them up. Amlodipine, nifedipine and many other calcium blockers ending in “-pine” work this way and are useful for blood pressure control and in people with spasm of blood vessels. An example is Raynaud’s phenomenon, where blood vessels constrict excessively in response to cold.
What you may have heard is that dietary calcium has very little or no effect on the action of calcium channel blockers, which is true. People on calcium channel blockers have the same dietary calcium needs as anyone else. Some calcium channel blockers, such as amlodipine (Norvasc and others), inhibit an enzyme (CYP3A4) that metabolizes some statin drugs, such as atorvastatin (Lipitor). This has the effect of raising the statin levels in the blood, so clinicians should be cautious in prescribing high doses of some statins in people taking calcium channel blockers.
Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu
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