[Drug-interactions and adverse effects of losartan potassium, an angiotensin II receptor antagonist].

Losartan potassium is mainly metabolized by P450 chiefly in the liver. A P450 inducer, phenobarbital, has no significant effects on the pharmacokinetics of losartan. Cimetidine, known to inhibit P450 activity, has no remarkable effects on the metabolism of losartan. Side effects of losartan has been very few in the clinical trials of this drug on several thousands of patients so far. The rate was as low as that of placebo. Losartan may cause hyperkalemia when used with potassium-sparing diuretics, such as spironolactone or triamterene. Angioedema and acute hepatitis had been reported in 3 patients among thousands of millions of hypertensives under losartan treatment. The etiology was unclear, simple coincidence may not be ruled out. Losartan should not be administered to pregnant women and breast-feeding mothers, because it may disturb the fetal growth or may be harmful to the newborn. It should be cautiously used in patients with renal failure or liver disfunction.