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chlorthalidone, Hygroton

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GENERIC NAME: chlorthalidone

BRAND NAME: Hygroton

DRUG CLASS AND MECHANISM: Chlorthalidone is a diuretic (water pill). It works by reducing the kidneys' ability to hold on to water and increasing the kidneys' production of urine (diuresis). Chlorthalidone is closely related chemically to hydrochlorothiazide. (Both are "thiazide" diuretics.) It was approved by the FDA in 1960.

GENERIC AVAILABLE: yes

PRESCRIPTION: yes

PREPARATIONS: Tablets: 15mg, 25mg, 50mg, 100mg.

STORAGE: Tablets should be stored at room temperature, 15-30°C (59-86°F).

PRESCRIBED FOR: Chlorthalidone is used in the treatment of high blood pressure and congestive heart failure.

DOSING: The optimal dose of chlorthalidone varies greatly from patient to patient.

DRUG INTERACTIONS: Chlorthalidone can cause lowering of blood potassium and magnesium levels because both potassium and magnesium are lost in the urine. This is especially true in patients who are taking at the same time another class of diuretics, called loop diuretics such as furosemide (Lasix), bumetanide (Bumex), or torsemide (Demadex) Low potassium and magnesium levels can lead to abnormal heart rhythms, especially in patients taking digoxin (Lanoxin).

Chlorthalidone reduces the kidney's ability to eliminate lithium in the urine. As a result, patients taking chlorthalidone at the same time as drugs containing lithium may develop high levels of lithium and lithium toxicity.

Nonsteroidal antiinflammatory drugs (NSAIDs) such as ibuprofen (Motrin), naproxen (Naprosyn), and nabumetone (Relafen) can reduce the effectiveness of chlorthalidone though the reason for this is not clear.

PREGNANCY: Thiazide diuretics including chlorthalidone cross the placenta and can cause jaundice in the fetus or newborn. Therefore, chlorthalidone should not be used during pregnancy unless absolutely necessary.

NURSING MOTHERS: The American Academy of Pediatrics recommends that breast-feeding be avoided during the first month of lactation (nursing) in patients receiving thiazide diuretics, including chlorthalidone, because production of milk may be suppressed.

SIDE EFFECTS: Chlorthalidone generally is well tolerated. Low blood levels of potassium, sodium, and magnesium may occur during chlorthalidone therapy due to their losses in urine. High blood calcium levels also can occur, especially in persons who are taking calcium supplements. Thiazide diuretics such as chlorthalidone increase the levels of uric acid in the blood, but gout (which is caused by high levels of uric acid) rarely occurs. Chlorthalidone can cause high blood sugars in diabetic patients. Other reported side effects include dizziness, lightheadedness, headache, fatigue, nausea, vomiting, abdominal pain, and constipation.

Reference: FDA Prescribing Information

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