Losartan potassium has no clinically significant drug interactions with hydrochlorothiazide, digoxin, warfarin, cimetidine, ketoconazole, erythromycin and phenobarbital.
Concomitant use of Losartan potassium and potassium-sparing diuretics (e.g. spironolactone triamterene, amiloride), potassium supplements, or salt substitutes containing potassium may lead to increase in serum potassium.
As like other antihypertensive agents, the antihypertensive effect of Losartan potassium may be decreased by indomethacin, the non-steroidal anti-inflammatory drug.
Concomitant use of rifampin and fluconazole may reduce levels of active metabolites.
Serum lithium levels should be monitored carefully, if co-administered with Losartan potassium.
In some patients with renal impairment who are being treated with non-steroidal anti-inflammatory drugs (NSAIDs), including selective cyclooxygenase-2 inhibitors (COX-II inhibitors), the concomitant use of Losartan potassium may result in further deterioration of renal function. These effects are usually reversible.