Irbesartan: CYP2C9 substrates/inhibitors eg, sulfaphenazole, tolbutamide & nifedipine. Hydrochlorothiazide: Digitalis glycosides; drugs that prolong QT interval eg, astemizole, terfenadine, halofantrine, pimozide & sotalol; neuromuscular blockers eg, atracurium; corticosteroids, corticotropin, β
2-agonists eg, salbutamol, carbenoxolone, amphotericin B or reboxetine; NSAIDs, pressor amines eg, noradrenaline, lithium, allopurinol, tetracyclines.