PROSPECTIVE EVALUATION OF 2 DOSING EQUATIONS FOR THEOPHYLLINE IN PREMATURE-INFANTS

Objectives. To evaluate prospectively the ability of two equations tha t we previously derived to predict maintenance theophylline dosages th at provide a serum theophylline concentration (STC) of 8 mu g/ml, the midtherapeutic range for treating apnea of prematurity; and to determi ne the number of further dosage adjustments and STC determinations req uired to achieve the target concentration in infants in whom it was no t achieved initially. Design. Prospective study. Setting. A 37-bed neo natal intensive care unit. Patients. Fifty-four infants 27-34 weeks' g estational age requiring intravenous hydrous aminophylline. Interventi ons. Patients received a loading dose of 6 mg/kg intravenous aminophyl line, followed by a maintenance dosage calculated using one of the two derived equations. The basis for equation selection was the gestation al age of the patient. Measurements and Main Results. Patients were st ratified into two age groups: 27-30 weeks' gestational age (34 infants ) and 31-34 weeks' gestational age (20 infants). The overall success r ate for both equations in achieving the target concentration was 74%. When infants were stratified by gestational age, those dosed by Equati on 1 had a 76% success rate and those dosed by Equation 2 had a 65% su ccess rate. Overall, 14 of 54 infants received an average of 1.2 dosag e adjustments. This represents more than a 50% reduction in the number of adjustments made before introduction of these equations. Conclusio ns. The ability of our previously derived equations to produce an STC within the midtherapeutic range for treating apnea of prematurity was demonstrated in the majority of patients studied (74%). Further, the n umber of subsequent dosage adjustments required to attain the target S TC in infants who had failed to achieve this STC initially was signifi cantly less than using older, more traditional regimens.