Lithium, K-containing salt substitutes, K-sparing diuretics, ACE inhibitors, angiotensin II receptor antagonists, heparin, ciclosporin, tacrolimus, trimethoprim. Diuretics. Reduced efficacy w/ NSAIDs or corticosteroids. Higher frequency of adverse events w/ combined use of ACE inhibitors, angiotensin II receptor blockers, or aliskiren.