BLOOD PRESSURE—TREATMENT: SIDE EFFECTS OF DIURETICS

Thursday, April 2, 2009 | 5:31 am

For more than 30 years, the Thiazide type of diuretics (water pills) have been the most widely used drugs for high blood pressure, but their safety is now in question. According to Geriatrics (39#1:40), there is a side effect of diuretics that can happen so gradually that it can quite easily be overlooked. By excessively reducing the body’s salt and water content, these medicines may also be reducing the blood volume so much that the blood pressure sinks dangerously low. Persons with extreme salt and water loss are likely to experience weakness, giddiness, and confusion, and may even faint and fall down, injuring themselves, when they suddenly try to stand. This effect, however, can be reversed by reducing the dose or giving some extra salt.

More recently, it has been discovered that some people taking a thiazide develop heartbeat irregularities, some of which are serious or even fatal. This risk, too, according to Drug Therapy (18#8:49), can be eliminated if the doctor gives some extra potassium and magnesium by mouth to prevent drug-induced depletion of these minerals from the body.

Most recently, thiazides have been found to increase cholesterol levels. Even worse, perhaps, is their effect on the “bad” LDL type of cholesterol, which increases by an average of 10 percent. Since no way of reversing this undesirable effect has been discovered, many doctors now use other diuretics instead.

Anyone whose cholesterol level is usually in the 150-180 mg range probably need not worry. But, for those with levels above normal, thiazide medication probably should be replaced.

However, a high blood pressure that rises out of control because of discontinued medication is more immediately dangerous than a high cholesterol level. One should therefore never discontinue or alter the dosage of a thiazide without the prescribing physician’s consent.

Actually, anyone who is taking a diuretic ought to monitor his blood pressure at home, taking his own readings or getting someone to do it for him. The doctor should be asked ahead of time about the lowest level that is safe, and, if the pressure falls below that, he should be told about it right away.

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