Enhancement of theophylline clearance by oral albuterol

The possible effect of albuterol on theophylline clearance was studied in ten adult volunteers. Subjects received intravenous aminophylline loading dose (5.6 mg/kg), with oral albuterol (4 mg every 6 h), or inhaled albuterol (200 μg every 6 h), or alone (control). Theophylline levels were determined for 12-h periods. Theophylline clearance and elimination t 1/2 were calculated. Theophylline clearance was significantly higher when given with oral albuterol, in comparison with control (0.83 ± 0.05 vs 0.73 ± 0.06 ml/kg/min, p<0.02). Theophylline elimination t 1/2 was shorter with the coadministration of oral albuterol, compared with control (7.1 ± 0.3 vs. 8.1 ± 0.6 h, p<0.02). These alterations in theophylline clearance and elimination were greater in subjects who had lower control theophylline clearance. Theophylline clearance and elimination t 1/2 recorded with inhaled albuterol were not significantly different from control values. Coadministration of oral albuterol and theophylline resulted in enhancement of theophylline clearance, particularly in subjects with initially slow theophylline elimination. Such patients may require theophylline dosage adjustment as a result of this interaction.