EFFECT OF SALBUTAMOL ON HISTAMINE-INDUCED BRONCHOCONSTRICTION IN HEALTHY INFANTS

Background-The effect of inhaled beta2 adrenergic drugs on infants wit h wheezing disorders remains controversial. Salbutamol inhibits the br onchial responsiveness of infants to histamine and nebulised water but whether or not it acts as a bronchodilator in this age group is uncle ar. The aim of the present study was to determine whether salbutamol c an hasten the reversal of histamine induced bronchoconstriction in inf ants. Methods-Bronchial challenge with histamine was performed in 40 i nfants aged 12 months or less with no previous history of respiratory symptoms. Response to histamine was assessed by forced partial expirat ory flow/volume curves to measure maximal flow at functional residual capacity (VmaxFRC). After a fall of 40% or more from baseline VmaxFRC, each infant was randomly assigned to receive either salbutamol 0.5% o r saline 0.9% solution by nebuliser. The rate of recovery of VmaxFRC a nd the time to reach baseline VmaxFRC were derived by linear regressio n. Results-Infants who received salbutamol had a significantly faster rate of recovery (geometric mean 8.5 ml/s/min) than those who received saline (4.1 ml/s/min). Considerable interindividual variation was obs erved in the time from maximum bronchoconstriction to recovery of base line VmaxFRC in both groups of subjects. Conclusion-Salbutamol signifi cantly speeds the reversal of histamine induced bronchoconstriction in infants during the first 12 months of life. This observation provides further evidence to support the presence of functional beta adrenergi c receptors in the airways of infants.