Olmesartan: May result in deterioration of renal function including possible acute renal failure w/ NSAIDs including selective COX-2 inhibitors. Antihypertensive effect may be attenuated w/ NSAIDs including selective COX-2 inhibitors. Increased risks of hypotension, hyperkalemia & changes in renal function (including acute renal failure) w/ dual blockade of the renin-angiotensin system w/ ARBs, ACE inhibitors or aliskiren. Reduced systemic exposure & peak plasma conc w/ colesevelam HCl. Increased serum lithium conc & toxicity. Amlodipine: Increased systemic exposure of simvastatin. May increase systemic exposure of cyclosporine or tacrolimus. Increased systemic exposure w/ moderate & strong CYP3A inhibitors. Closely monitor BP in co-administration w/ CYP3A inducers. Hydrochlorothiazide: Adjust dose of concomitant antidiabetic drugs (oral agents & insulin). Reduced absorption w/ cholestyramine or colestipol resins. Intensified electrolyte depletion particularly hypokalemia w/ corticosteroids, ACTH. Reduced diuretic, natriuretic & antihypertensive effects w/ NSAIDs.