Losartan K: Potentiated antihypertensive effects w/ other drugs that lower BP. Additive hyperkalaemic effects w/ K supplements, K-sparing diuretics or other drugs that cause hyperkalaemia. Increased risk of renal impairment & attenuate hypotensive effect w/ NSAIDs. Hydrochlorothiazide: May potentiate orthostatic hypotension w/ alcohol, barbiturates, narcotics & antidepressants. Risk of lactic acidosis w/ metformin.