Additive bronchodilator effects of terbutaline and enprofylline in asthma

Enprofylline is a novel xanthine derivative with negligible adenosine antagonizing ability. It is eliminated almost exclusively by renal clearance with a half-life of about 2 h. Three i.v. infusions of enprofylline (1 mg/kg body weight over 10 min) were given at hourly intervals to 16 patients with stable, reversible airway obstruction. The patients were pretreated at random with i.v. terbutaline (4 micrograms/kg body weight) or placebo according to a double blind cross-over design. Lung function and drug concentrations in plasma were followed. Enprofylline produced significant and concentration-dependent bronchodilation between plasma levels of 1.24 and 3.22 mg/l. The improvement in ventilatory function was significantly enhanced by terbutaline pretreatment. At the highest plasma levels of enprofylline nausea and headache were found as subjective side effects. The results suggest that enprofylline and terbutaline might best be used in a low dose combination in the treatment of bronchial asthma.