Dosing must be individualised. The usual starting dose of Losartan is 50 mg once daily, with 25 mg recommended for patients with intravascular volume depletion (e.g., patients treated with diuretics) and patients with a history of hepatic impairment. Losartan can be administered once or twice daily at total daily doses of 25 to 100 mg. If the antihypertensive effect measured trough using once a day dosing is inadequate, a twice a day regimen at the same total daily dose or an increase in dose may give a more satisfactory response.
Hydrochlorothiazide is effective in doses of 12.5 to 50 mg once daily and can be given at doses of 12.5 to 25 mg. To minimise dose independent side effects, it is usually appropriate to begin combination therapy only after a patient has failed to achieve the desired effect with monotherapy
Losartan is an angiotensin II receptor antagonist. It selectively and competitively blocks the vasoconstricting and aldosterone-secreting effects of angiotensin II by selectively antagonising its binding to AT1 receptors.
Hydrochlorothiazide inhibits the reabsorption of Na in the distal tubules causing increased excretion of Na and water including K and hydrogen ions.