Aminophylline loading in asthmatic patients: a protocol trial

We tested an aminophylline loading-dose protocol in which asthmatic patients presenting to an emergency department were given a half (3 mg/kg) IV loading dose based on total body weight (TBW) if they had taken a short-acting or sustained-release theophylline preparation within 12 or 24 hours, respectively, prior to arrival: otherwise, a full (6 mg/kg) loading dose was administered. Of the 28 patients given a full loading dose, 20 (71.4%) achieved a postload therapeutic level (10 to 20 micrograms/mL), and none developed a toxic level (greater than 20 micrograms/mL). Although 34 (60.7%) of 56 patients given a half loading dose attained a postload therapeutic level, 13 patients (23.2%) entered the toxic range. We were able to predict that loading doses of 7.6 mg/kg and 3.8 mg/kg based on ideal body weight (IBW) would have yielded very similar results. The mean change in theophylline level per mg/kg TBW of administered aminophylline was 2.01 micrograms/mL. When calculated on the basis of IBW, the mean change in theophylline level was 1.58 micrograms/mL. Evaluation of the change in theophylline level resulting from aminophylline loading doses based on either TBW or IBW revealed that each dosing method produced changes in blood level with similar variability that were not independent of obesity, indicating that neither dosing method is superior to the other. Thus, patients who report not having taken a theophylline preparation within the above time limits can be given a full aminophylline loading dose of either 6 mg/kg based on TBW or 7.6 mg/kg based on IBW. Other patients, however, require a preload blood level determination to optimize therapy and avoid toxic levels.(ABSTRACT TRUNCATED AT 250 WORDS)