Losartan potassium, hydrochlorothiazide.
50 mg/12.5 mg FC tab: Each film-coated tablet contains: Losartan Potassium 50 mg and Hydrochlorothiazide 12.5 mg.
100 mg/25 mg FC tab: Each film-coated tablet contains: Losartan Potassium 100 mg and Hydrochlorothiazide 25 mg.
Pharmacology: Losartan Potassium: Angiotensin II is a potent vasoconstrictor, the primary vasoactive hormone of the renin-angiotensin system and an important component in the pathophysiology of hypertension. It also stimulates aldosterone secretion by the adrenal cortex. Losartan and its principal active metabolite block the vasoconstrictor and aldosterone-secreting effects of angiotensin II by selectively blocking the binding of angiotensin II to the AT1 receptor found in many tissues. There is also an AT2 receptor found in many tissues but is not known to be associated with cardiovascular homeostasis. In vitro binding studies indicate that losartan is a reversible, competitive inhibitor of the AT1 receptor. The active metabolite is 10-40 times more potent by weight than losartan and appears to be a reversible, non-competitive inhibitor of the AT1 receptor.
Neither losartan nor its active metabolite inhibits ACE, nor do they bind to or block other hormone receptors or ion channels known to be important in cardiovascular regulation.
Hydrochlorothiazide (HCTZ): Hydrochlorothiazide is a thiazide diuretic. Thiazides increase the excretion of water by inhibiting the reabsorption of sodium and chloride ions at the distal renal tubule. The natriuretic effects are accompanied by a secondary loss of potassium and bicarbonate which can cause a mild hypokalemic, hypochloremic, metabolic alkalosis. Thiazides also decrease the elimination of calcium and uric acid. Thiazide diuretics usually do not affect normal blood pressure. When chronically administered, thiazide diuretics decrease peripheral vascular resistance. The exact mechanism responsible for lowered peripheral resistance is not known, however, excretion of urinary sodium by the kidneys is required to achieve blood pressure reduction. Initially, diuretics lower blood pressure by decreasing cardiac output, plasma volume and extracellular fluid volume. Cardiac output eventually returns to normal, plasma and extracellular fluid values return slightly less than normal, but peripheral vascular resistance is reduced, resulting in lower blood pressure.
Pharmacokinetics: Losartan is readily absorbed from the gastrointestinal tract after oral doses, but undergoes substantial first-pass metabolism resulting in a systemic bioavailability of about 33%. It is metabolized to an active carboxylic acid metabolite E-3174 (EXP-3174), which has greater pharmacological activity than losartan; some inactive metabolites are also formed. Metabolism is primarily by cytochrome P450 isoenzymes CYP2C9 and CYP3A4. Peak plasma concentrations of losartan and E-3174 occur about 1 hour and 3 to 4 hours, respectively, after an oral dose. Both losartan and E-3174 are more than 98% bound to plasma proteins. Losartan is excreted in the urine, and in the faeces via bile, as unchanged drug and metabolites. About 4% of an oral dose is excreted unchanged in urine and about 6% is excreted in urine as the active metabolite. The terminal elimination half-lives of losartan and E-3174 are about 1.5 to 2.5 hours and 3 to 9 hours, respectively.
Hydrochlorothiazide is fairly rapidly absorbed from the gastrointestinal tract. It is reported to have a bioavailability of about 65 to 70%. It has been estimated to have a plasma half-life of between about 5 and 15 hours and appears to be preferentially bound to red blood cells. It is excreted mainly unchanged in the urine. Hydrochlorothiazide crosses the placental barrier and is distributed into breast milk.
For the treatment of essential hypertension in patients whose blood pressure is not adequately controlled on losartan or hydrochlorothiazide alone.
Usual adult dose of 1 to 2 tablet daily. Maybe taken with or without food or as prescribed by the physician.
Hypersensitivity to any component of Losartan Potassium, Hydrochlorothiazide and to sulfonamide-derived drugs; anuria. Pregnancy.
This product contains FD & C yellow # 5 (tartrazine) which may cause allergic type reactions (including bronchial asthma) in certain susceptible persons.
Severe renal or hepatic impairment; patients with bilateral renal artery stenosis. Lactation.
Use in pregnancy: When used in pregnancy during the 2nd and 3rd trimesters, drugs that act on the renin-angiotensin system (eg, losartan) can cause injury and even death to the developing fetus. When pregnancy is detected, discontinue losartan as soon as possible.
Abdominal pain, edema, asthenia, headache; palpitation; diarrhea, nausea; back pain; dizziness; dry cough, sinusitis, bronchitis, pharyngitis, upper respiratory infection. Rash.
Losartan: Cimetidine, phenobarbital, rifampicin, fluconazole; K-sparing diuretics, K supplements.
Hydrochlorothiazide: Alcohol, barbiturates or narcotics; antidiabetic agents; cholestyramine, colestipol resins; corticosteroids, tubocurarine, lithium & NSAIDs.
Store at temperatures not exceeding 30°C.
C09DA01 - losartan and diuretics ; Belongs to the class of angiotensin II receptor blockers (ARBs) in combination with diuretics. Used in the treatment of cardiovascular disease.
50 mg/12.5 mg FC tab 30's. 100 mg/25 mg FC tab 30's.