Attempts to wean ventilator-dependent infants with BPD have been made by trying to reduce bronchospasm using β agonist drugs or caffeine. However, all drugs tested to date were not β2 selective and their use has been associated with unaccepted tachycardia. We studied the pharmacokinetics and respiratory dynamics of salbutamol after an IV infusion of 1 μg/kg/mn over 30 min. Our patients were 6 ventilatory dependent infants with BPD (24-28 wks gest. age; 50-90 days postnatal age). Serum concentrations were measured by a new HPLC method. Elimination T1/2 of salbutamol was 133 ± 27 min (mean ± SEM). Calculated distribution volume was 129 ± 397 ml/kg and clearance rate of 7.5 ± 2.6 ml/kg/min. The shorter T1/2 in these patients when compared to healthy adults or patients with CF may be explained by smaller Vd in the presence of comparable clearance. Passive expiratory, total respiratory system compliance (CRS) improved in all infants (mean 23%) though in only 5/6 was this an immediate effect. Airflow resistance decreased in 5/6 patients, (mean 23.3%). No consistent changes lasting for more than 1 hour were seen with Tc O2, Tc CO2, arterial or capillary CO2 or O2. All 6 infants developed tachycardia (from158±2/min to202 ± 6/min), which peaked at the end of the infusion. There was a significant positive correlation between Vd and % change in heart rate. Traditionally, it was thought that during the postnatal period β agonists do not exert bronchodilatatory effects due to the lack of β2 receptors. The present study indicates that the emergence of these receptors starts to take place in the postnatal period.
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Koren, G., Kimalani, H., Schmidt, B. et al. PHARMACOKINETICS AND RESPIRATORY PHARMACODYNAMICS OF IV SALBUTAMOL IN NEONATES WITH BRONCHOPULMONARY DYSPLASIA. Pediatr Res 21, 236 (1987). https://doi.org/10.1203/00006450-198704010-00415