Medications and Drugs
Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD
GENERIC NAME: triamterene and hydrochlorothiazide (HCTZ)
BRAND NAMES: Maxzide, Dyazide
DRUG CLASS AND MECHANISM: 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 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.
PRESCRIPTION: Yes
GENERIC AVAILABLE: Yes
PREPARATIONS: Tablets: 37.5/25, 75/50 mg. Capsules: 37.5/25, 50/25 mg.
STORAGE: Triamterene/hydrochlorothiazide should be store at room
temperature, 15-30 C (59-86 F).
PRESCRIBED FOR: Triamterene/hydrochlorothiazide is used for treating
high blood pressure and edema.
DOSING: 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.
DRUG INTERACTIONS: 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.
Blood sugar levels can be elevated by hydrochlorothiazide necessitating
adjustment in the doses of medications that are used for treating diabetes.
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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