Thiazide diuretics like hydrochlorothiazide (Esidrix, HydroDIURIL, other brands) continue to be a very effective way to lower blood pressure for people with hypertension. They're inexpensive, and results from large studies have shown them to be at least as effective as other types of blood pressure drugs for most patients.
But if you're taking a diuretic, your potassium levels need to be watched. These drugs direct the kidneys to pump water and sodium into the urine. Unfortunately, potassium also slips through the open floodgates. A low potassium level can cause muscle weakness, cramping, or an abnormal heartbeat, which is especially dangerous for people with heart problems.
Potassium pills are one solution, but some tend to taste bad, so people may neglect to take them. Eating foods rich in potassium, like bananas, may help, but often that's not enough. Spironolactone (Aldactone) and triamterene (Dyrenium) are diuretics that "spare" potassium, leaving levels high, but they're pretty weak as diuretics. Dyazide (available as a generic) is an attempt to strike a balance: It's part thiazide, part potassium-sparing diuretic.
Taking a potassium-sparing diuretic may be especially important if you have heart failure. Diuretics are often used to fight or prevent swelling in people with heart failure, but taking a potassium-sparing diuretic helps people with heart failure feel better, stay out of the hospital, and live longer. Heart failure patients taking the potassium-sparing diuretic are less likely to die or be hospitalized than those taking only regular diuretics.