Increase in serum lithium conc. Deterioration of renal function, including possible acute renal failure w/ NSAIDs including selective COX-2 inhibitors in patients who are elderly, vol-depleted (including those on diuretic therapy), or w/ compromised renal function. Increased risk of hypotension, syncope, hyperkalemia, & changes in renal function (including acute renal failure) w/ ARBs, ACE inhibitors, or aliskiren. Concomitant use w/ antidiabetic drugs. Additive effect or potentiation w/ other antihypertensive drugs. Losartan: May result in hyperkalemia w/ agents increasing serum K. NSAIDs including COX-2 inhibitors may attenuate antihypertensive effect. Hydrochlorothiazide: Impaired absorption w/ cholestyramine & colestipol. Potentiation of orthostatic hypotension w/ alcohol, barbiturates, or narcotics. Possible increased responsiveness to skeletal muscle relaxants, nondepolarizing (eg, tubocurarine). May intensify electrolyte depletion, particularly hypokalemia w/ corticosteroids, ACTH, or glycyrrhizin. Decreased response to pressor amines eg, norepinephrine.