Theophylline concentrations in asthmatic patients after administration of aminophylline

To test the efficacy of using a weight-derived formula to determine aminophylline dosages, 50 patients hospitalized for treatment of severe asthma were given intravenous aminophylline infusions at a rate of 0.9 mg/kg/hr to a maximum dosage of 1,500 mg/24 hr. Serum theophylline determinations done 12 to 96 hours after institution of this therapy showed levels greater than 20 mg/liter in 34% of these patients. Reliance on weight-derived formulas can be dangerous.