Aminophylline, salbutamol and combined intravenous infusions in acute severe asthma

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 or 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 24 hours as follows: 1. Aminophylline 0.285 mg/kg/min for 15 min followed by 0.014 mg/kg/min (20 mg/min. followed by 1 mg/min for a 70 kg subject). 2. Salbutamol 0.285 microgram/kg/min for 15 min followed by 0.057 microgram/kg/min (20 microgram/min followed by 4 microgram/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 amd 35% oxygen given via a Ventimask. Peak expiratory flow rates showed a significant improvement after 15 minutes treatment 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.