Losartan belongs to a class of drug known as angiotension II receptor antagonists, which directly blocks the angiotensin II (a potent vasoconstrictor). This drug prevents the constriction (narrowing) of blood vessels (veins and arteries).
Indications: Management of hypertension (high blood pressure). Reduction in the risk of cerebrovascular accidents (CVA) or stroke and cardiovascular morbidity and mortality in hypertensive patients with left ventricular hypertrophy (LVH). Renal protection in patients with type 2 diabetes mellitus with proteinuria .
Special precautions: severe renal or hepatic impairment; bilateral renal artery stenosis; patients on a salt-restricted diet; hyperkalemia (increase potassium levels in the blood) or those taking potassium-sparing diuretics (water pill) or potassium supplements. Pregnancy, lactation and children. Pregnancy especially during the second and third trimesters because it can cause injury or even death to the developing fetus (US FDA category D). Alcohol intake may further lower blood pressure and increase drowsiness and dizziness, so use alcohol cautiously. Use with caution when driving, operating machinery or other hazardous activities that requires you to be fully awake and in alert state.
Losartan can be taken with or without food and with full glass of water. It is important to regularly take this medicine to ensure adequate control of blood pressure. Have your blood pressure & blood chemistry checked with a followup evaluation by your doctor to properly monitor progress and response while treatment with losartan. Symptoms of a losartan overdose are not well known but might include dizziness, weakness, fainting and fatigue due to hypotension (decrease blood pressure). Seek emergency consult once you experience the above suspected symptoms of overdose.
Serious adverse reactions: anuria (little or no urine output); an allergic reaction (difficulty of breathing, closing of throat, swelling of the lips, tongue, face or hives), hyperkalemia. Less serious side effects: diarrhea or abdominal pain , nausea, headache, palpitations, dry cough, myalgia (muscle pain or cramps), dizziness or dose-related orthostatic effects (due to hypotension), rash, fatigue/asthenia, vertigo. In general, the adverse reactions are mostly gastrointestinal, cardiovascular, hematologic, musculoskeletal, nervous, psychiatric, respiratory and dermatologic in origin.
Drug interactions: increase in serum potassium level with potassium-sparing diuretics such as amiloride (Midamor); spironolactone (Aldactone), or triamterene (Dyrenium, Dyazide, Maxzide) or salt substitutes containing potassium. Potassium supplements such as K-Dur, Klor-Con and others. Antihypertensive effect may be attenuated by indomethacin. Rifampicin & fluconazole reduce levels of active metabolite. You may not be able to take losartan, or you may require a dosage adjustment or special monitoring if you are taking any of the medicines listed above. Tell your doctor about any other medicines you take to treat high blood pressure or other heart conditions.
Losartan potassium is a white to off-white free-flowing crystalline powder with a molecular weight of 461.01. It is freely soluble in water, soluble in alcohols, and slightly soluble in common organic solvents, such as acetonitrile and methyl ethyl ketone. Oxidation of the 5-hydroxymethyl group on the imidazole ring results in the active metabolite of losartan. Losartan is available as tablets for oral administration containing either 25 mg, 50 mg or 100 mg of losartan potassium and the following inactive ingredients: microcrystalline cellulose, lactose hydrous, pregelatinized starch, magnesium stearate, hydroxypropyl cellulose, hypromellose, titanium dioxide, D&C yellow No. 10 aluminum lake and FD&C blue No. 2 aluminum lake.
Losartan has the following structural formula: