Aliskiren. Losartan: Reduced levels of active metabolite w/ rifampin & fluconazole. May increase serum K level w/ K-sparing diuretics (eg, spironolactone, triamterene, amiloride), K supplements salt substitutes containing K, or other drugs that may increase serum K (eg, trimethoprim-containing products). May reduce lithium excretion. Antihypertensive effects may be attenuated by NSAIDs including COX-2 inhibitors. Further deterioration of renal function w/ ACE inhibitors. Dual blockade of RAAS w/ angiotensin receptor blockers, ACE inhibitors or aliskiren is associated w/ increased risk of hypotension, syncope, hyperkalemia & changes in renal function. Hydrochlorothiazide: Potentiation of orthostatic hypotension w/ alcohol, barbiturates or narcotics. Antidiabetics (oral agents & insulin). Additive effects w/ other antihypertensives. Impaired absorption w/ cholestyramine & colestipol resins. Intensified electrolyte depletion particularly hypokalemia w/ corticosteroids, ACTH, or glycyrrhizin. Possible decreased response to pressor amines eg, adrenaline. Possible increased responsiveness to nondepolarizing skeletal muscle relaxants eg, tubocurarine. Reduced renal clearance of lithium & high risk of lithium toxicity. Reduced diuretic, natriuretic & antihypertensive effects by NSAIDs including COX-2 inhibitors.