Increased risk of hyperkalemia w/ salt substitutes containing K, K-sparing diuretics, ACE inhibitors, AIIA, NSAIDs (including selective COX-2 inhibitors), heparin, immunosuppressives (cyclosporin or tacrolimus), & trimethoprim. Increased serum K w/ K-sparing diuretics (eg, spironolactone, eplerenone, triamterene, or amiloride), K supplements, or K-containing salt substitutes. Reversible increases in serum lithium conc & toxicity. May reduce antihypertensive effect w/ NSAIDs (ie, ASA at anti-inflammatory dosage regimens, COX-2 inhibitors & non-selective NSAIDs). Vol depletion & risk of hypotension w/ high dose diuretics eg, furosemide (loop diuretic) & hydrochlorothiazide (thiazide diuretic). Increased BP lowering effect w/ other antihypertensive agents. May potentiate hypotensive effects w/ baclofen & amifostine. May aggravate orthostatic hypotension w/ alcohol, barbiturates, narcotics, or antidepressants. Reduced antihypertensive effect w/ corticosteroids (systemic route).