losartan and hydrochlorothiazide, Hyzaar
Omudhome Ogbru, PharmD
Omudhome Ogbru, PharmD
Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.
Medical and Pharmacy Editor:
GENERIC NAME: losartan and hydrochlorothiazide
BRAND NAME: Hyzaar
DRUG CLASS AND MECHANISM: Hyzaar is a combination of losartan (Cozaar) and hydrochlorothiazide and is used for treating high blood pressure. Losartan is an oral medication that belongs to a class of drugs called angiotensin receptor blockers (ARBs). Other ARBs include irbesartan (Avapro), valsartan (Diovan), and candesartan (Atacand). Angiotensin, formed in the blood by the action of angiotensin converting enzyme (ACE), is a powerful chemical that attaches to angiotensin receptors found in many tissues but primarily on smooth muscle cells surrounding blood vessels. Angiotensin's attachment to the receptors causes the muscles to contract and the blood vessels to narrow (vasoconstrict) which leads to an increase in blood pressure (hypertension). Losartan (more specifically, the chemical formed when the liver converts the inactive losartan into an active chemical) blocks the angiotensin receptor. By blocking the action of angiotensin, losartan relaxes the muscles, dilates blood vessels and thereby reduces blood pressure.
Hydrochlorothiazide (HCTZ) is a diuretic (water pill) used for treating high blood pressure (hypertension) and accumulation of fluid. It works by blocking salt and fluid reabsorption in the kidneys, causing an increased amount of urine containing salt (diuresis). The mechanism of its action in lowering high blood pressure is not well understood. The combination of losartan and HCTZ reduces blood pressure better than either drug alone. Losartan increases potassium levels while HCTZ reduces potassium levels; the combination of both drugs has less effect on potassium levels. The FDA approved Hyzaar in April 1995.
GENERIC AVAILABLE: Yes
PREPARATIONS: Tablets (HCTZ/losartan): 12.5/50 mg, 12.5/100 mg, and 25/100 mg
STORAGE: Tablets should be stored at room temperature, between 15-30 C (59-86 F) and protected from excessive light and humidity. They should be kept in a tightly-closed, light-resistant container.
PRESCRIBED FOR: Hyzaar is used to treat patients with high blood pressure and for reducing the risk of stroke in patients with high blood pressure and left ventricular hypertrophy.
DOSING: The usual starting dose is 12.5/50 mg of Hyzaar once daily for patients not controlled on losartan or HCTZ treatment alone. The dose may be increased after 3 weeks to 2 tablets of 12.5/50 mg or one tablet of 25/100 mg daily. Patients who have not been controlled on losartan 100 mg alone should be switched to Hyzaar 12.5/100 mg.
DRUG INTERACTIONS: Losartan may increase levels of blood potassium which can lead to serious heart problems (arrhythmias). Therefore, concomitant use of other substances that increase blood potassium-such as potassium-sparing diuretics (for example, spironolactone (Aldactone), triamterene, and amiloride), potassium supplements, or salt substitutes containing potassium may lead to dangerous increases in serum potassium.
Combining losartan or other ARBs with nonsteroidal anti-Inflammatory drugs (NSAIDs) in patients who are elderly, volume-depleted (including those on diuretic therapy), or with poor kidney function may result in reduced kidney function, including kidney failure. These effects usually are reversible. The antihypertensive effect of losartan may be reduced by aspirin and other NSAIDs such as ibuprofen (Advil, Children's Advil/Motrin, Medipren, Motrin, Nuprin, PediaCare Fever, etc.), indomethacin (Indocin, Indocin-SR), and naproxen (Anaprox, Naprelan, Naprosyn, Aleve). HCTZ reduces the elimination of lithium (Lithobid, Eskalith) by the kidneys and can lead to lithium toxicity. NSAIDs, for example, ibuprofen, may reduce the blood pressure effects of hydrochlorothiazide.
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