Triamterene/hydrochlorothiazide is an oral diuretic (water pill) that is used for treating high blood pressure (hypertension) and edema (water accumulation). It is a combination of two different diuretics. The FDA approved triamterene/hydrochlorothiazide in December 1965.

The kidneys control the amount of sodium and water within the body. Normally, blood circulates through the kidneys where much of the water, sodium and other small molecules are filtered out of the blood and into the tubules of the kidney. Once in the tubules, much of the water and sodium are reabsorbed back into the blood. The water and sodium that is not reabsorbed passes on through the tubules and becomes urine that is eliminated from the body. Diuretics affect the reabsorption of sodium and water from the tubules and thus, the amount of sodium and water retained or eliminated by the body. In addition to controlling sodium, the kidney also controls the amount of potassium that is retained or eliminated from the body.

Diuretics eliminate salt (sodium) and water from the body. Hydrochlorothiazide is a diuretic that can be used alone for treating high blood pressure and edema. It works by blocking sodium and water reabsorption in the kidneys, thereby reducing sodium and water in the body. (Whereas it is clear how hydrochlorothiazide eliminates water from the body, its mechanism of action in lowering high blood pressure is not well understood.) To compensate for the increased amount of sodium and water in the tubules that will be lost as urine, the kidney tries to reabsorb more sodium and water. It does this by removing potassium from the blood and putting it into the tubules in exchange for sodium (and water) in the tubules. As a result, blood potassium levels fall. Triamterene is a diuretic that prevents reabsorption of sodium in exchange for potassium. Thus, it reduces sodium and water in the body but also prevents the depletion of potassium. For this reason, triamterene is called a potassium sparing diuretic. By combining hydrochlorothiazide with triamterene, sodium and water are eliminated from the body without the loss of potassium. However, this drug may allow potassium levels to increase so potassium levels should be closely monitored.

Maxzide, Dyazide

GENERIC AVAILABLE: Yes

Yes

Side effects of triamterene/hydrochlorothiazide include abdominal pain, nausea, vomiting, rash, headache, dizziness, constipation, low blood pressure, electrolyte disturbance (for example, high potassium levels), muscle cramps, hypersensitivity, pancreatitis, and jaundice. Triamterene/hydrochlorothiazide may increase blood sugar (glucose) levels and precipitate or worsen diabetes. Patients allergic to sulfa drugs may also be allergic to hydrochlorothiazide because of the similarity in the chemical structure of the two drugs.

The recommended dose is 1-2 tablets or capsules daily. The maximum dose is 75/50 mg daily. Like other diuretics, it should be taken in the morning in order to avoid excessive trips to the bathroom at night.

Triamterene increases potassium levels in the body. Therefore, combining triamterene/hydrochlorothiazide with ACE inhibitors [for example, enalapril (Vasotec)], angiotensin receptor blockers [for example, losartan (Cozaar)], aliskiren (Tekturna), eplerenone (Inspra), potassium supplements or other drugs that also increase potassium may lead to dangerous potassium levels in the body.

Salt substitutes (for example, Mrs. Dash) contain potassium and may lead to excessive potassium levels in the body if combined with triamterene/hydrochlorothiazide.

Hydrochlorothiazide increases blood levels of dofetilide (Tikosyn), increasing the adverse effects of dofetilide.

Hydrochlorothiazide reduces the elimination of lithium (Lithobid) by the kidneys, increasing blood levels of lithium and lithium toxicity. Nonsteroidal antiinflammatory drugs, for example, ibuprofen, may reduce the blood pressure-reducing effects of triamterene/hydrochlorothiazide.

Combining hydrochlorothiazide with corticosteroids may increase the risk for low levels of blood potassium and other electrolytes. Low blood potassium can increase the toxicity of digoxin (Lanoxin).

Cholestyramine (Questran, Questran Light) and colestipol (Colestid) bind to hydrochlorothiazide and reduce its absorption from the gastrointestinal tract by 43%-85%.

Blood sugar levels can be elevated by hydrochlorothiazide necessitating adjustment in the doses of medications that are used for treating diabetes.

Triamterene/hydrochlorothiazide has not been adequately studied in pregnant women.

 Triamterene/hydrochlorothiazide has not been evaluated in nursing mothers. Hydrochlorothiazide is excreted in breast milk. Intense diuresis using hydrochlorothiazide may reduce the production of breast milk. Otherwise, hydrochlorothiazide is considered safe to use during nursing if required by the mother.

What preparations of triamterene and hydrochlorothiazide are available?

Tablets: 37.5/25, 75/50 mg. Capsules: 37.5/25, 50/25 mg.

How should I keep triamterene and hydrochlorothiazide stored?

Triamterene/hydrochlorothiazide should be store at room temperature, 15 C - 30 C (59 F - 86 F).