Infraadditive diuretic efficacy of concurrent aminophylline and frusemide

Male albino rats weighing between 150-225 gm fasted over night but freed having water ad libitum were used to assess the diuretic efficacy of intramuscular aminophylline and frusemide separately and concurrently after intraperitoneal 10 ml of distilled water loading. The normal rate of diuretic weight loss was less augmented by aminophylline and more augmented by frusemide. The diuretic response was more by the concurrent intramuscular administration of aminophylline and frusemide in comparison with that due to either drug alone. However, the observed diuretic response of the two drugs administered concurrently was lesser (infraadditive) than the sum of the individual diuretic response (additive).