Medications and Drugs
Medical and Pharmacy Editor: Jay W. Marks, MD
GENERIC NAME: losartan
BRAND NAME: Cozaar
DRUG CLASS AND MECHANISM: 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 of blood vessels. Angiotensin's attachment
to the receptors causes 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 dilates blood vessels and thereby reduces blood pressure.
Losartan was approved by the FDA in April, 1995.
PRESCRIPTION: Yes
GENERIC AVAILABLE: No
PREPARATIONS: Tablets: 25, 50 and 100 mg
STORAGE: Tablets should be stored at room temperature in a tightly closed,
light resistant container.
PRESCRIBED FOR: Losartan is used for treating hypertension, left ventricular
hypertrophy (increase in muscle) and diabetic nephropathy (kidney disease). It
may be used alone or in combination with other drugs.
DOSING: The usual starting dose of losartan for adults is 50 mg daily. The
maximum dose is 100 mg daily. The total daily dose may be divided and
administered twice daily. Losartan may be given with or without food.
The starting dose of losartan for pediatric patients 6 years of age or older
is 0.7 mg/kg up to 50 mg once daily. Doses more than 1.4 mg/kg or 100 mg daily
have not been evaluated in pediatric patients.
DRUG INTERACTIONS: Inhibitors of cytochrome P450 enzymes such as fluconazole
(Diflucan) reduced the formation of the active drug metabolite in laboratory
studies. Therefore, caution should be used when adding losartan in a patient
taking Nizoral, as reduced activity of losartan may occur.
Losartan may increase levels of blood potassium which can lead to serious
heart problems (arrhythmias). Therefore, concomitant use of other substances
that increase blood-such as potassium-sparing diuretics (e.g., spironolactone,
triamterene, and amiloride), potassium supplements, or salt substitutes
containing potassium--may lead to dangerous increases in serum potassium.
The antihypertensive effect of losartan may be reduced by nonsteroidal
antiinflammatory drugs (e.g., indomethacin, ibuprofen, aspirin , and naproxen).
PREGNANCY: When used in the
second or third trimester of pregnancy , drugs
that act by the same mechanism as losartan (ARBs) can cause injury and even
death to the fetus. Losartan should not be used during pregnancy. When pregnancy
is first detected, losartan should be stopped as soon as possible.
NURSING MOTHERS: It is not
known whether losartan is excreted in breast milk ,
but losartan and its active metabolite are excreted in rat milk. Due to the
possibility of harm to the nursing infant, if possible, losartan should be
discontinued by nursing mothers.
SIDE EFFECTS: In clinical studies the overall incidence of side effects was
similar to placebo. Side effects reported included diarrhea, muscle cramps,
dizziness, insomnia, and nasal congestion. Losartan also may cause a persistent
cough, increase serum potassium, and angioedema. Losartan may reduce kidney
function in some patients and should not be used by patients who have bilateral
renal artery stenosis (narrowing of both arteries going to the kidneys). Rare
cases of rhabdomyolysis (muscle breakdown) have been reported.
Reference: FDA Prescribing Information
Last Editorial Review: 10/9/2006
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