<p>Combination with other antihypertensive agents such as b blockers, Methyldopa, calcium antagonists and diuretics may increase the antihypertensive efficacy. Adrenergic blocking drugs should only be combined with Enalapril under careful supervision. Concomitant Propranolol may reduce the bioavailability of Enalapril, but this does not appear to be of any clinical significance. Concomitant therapy with Lithium may increase the serum Lithium concentration.</p>