Br. J. Dis. Chest (1980) 74, 385 AMINOPHYLLINE, SALBUTAMOL AND COMBINED INTRAVENOUS INFUSIONS IN ACUTE SEVERE ASTHMA W. V. EVANS, ° R. D. H. MONIE, J. CRIMMINSAND A. SEATON Welsh National School of Medicine; Llandough and Sully Hospitals, Penarth, South Glamorgan; Institute of Occupational Medicine, Edinburgh Summary Twenty-one patients admitted to hospital with acute severe asthma were allocated in a random, single-blind manner to receive intravenous infusions for 24 hours of either aminophylline or salbutamol or a combination of the two drugs. Infusions were administered by a slow infusion pump with an initial loading dose given over 15 minutes, followed by a continuous lower dose of the drug for 24 hours as follows: 1. Aminophylline 0.285 mg/kg/min for 15 rain followed by 0.014 mg/kg/min (20 mg/ min. followed by 1 mg/min for a 70 kg subject). 2. Salbutamol 0.285/~g/kg/min for 15 min followed by 0.057/~g/kg/min (20/zg/min followed by 4 ~gm/min for a 70 kg subject). 3. Combined regimen of the above infusions. In addition each patient received intravenous hydrocortisone (4 g) and potassium chloride (4 g) in 2 litres of 5% dextrose infused over 24 hours and 35% oxygen given via a Ventimask. Peak expiratory flow rates showed a significant improvement after 15 minutes treat- ment with aminophylline and the combined infusion, but this was not seen until 60 minutes with the salbutamol infusion. No synergistic bronchodilator effect was seen with the combined infusion. The results show that intravenous aminophylline is superior to intravenous salbutamol in the doses given in the initial treatment of acute asthma and that the combination when given intravenously is not better than aminophylline alone. INTRODUCTION Bronchodilators and corticosteroids are used routinely in the treatment of acute asthma. Two effective bronchodilators are aminophylline, a phosphodiesterase inhibitor, and salbutamol, a selective fi2 adrenoceptor agonist. Because these drugs act at different sites in the metabolic pathway of cyclic AMP, when used together they might be expected to act additively or even synergistically. Such interaction has in fact been demonstrated in the laboratory (Kaliner et al. 1971) and in stable asthmatics (Campbell et al. 1977). This study was designed to show whether such a beneficial interaction occurred between intravenous aminophylline and intravenous salbutamol in acute severe asthma. * Present address: Senior Medical Registrar, Whiston Hospital, Prescot L35 5DR. 37