Aim: Therapeutic aerosols are routinely used in the management of infant obstructive airways disease. Infants often become distressed during administration. The aim of this study was to determine the influence of distress and disease severity on the absorption of aerosolised drug in this age group.
Methods: Fifteen infants, eight with resolving chronic lung disease of prematurity (mean age, 13 months), and seven infants with normal birth histories (mean age, 11 months) were studied. Flow through small airways was assessed by measurement of partial forced expiratory flow volume curves. Each infant was then given a dose of 20 mg nebulised sodium cromoglicate via a Sidestream nebuliser and distress was graded as: 1, not distressed; 2, distressed. Infants were excluded if contact with the mask was lost for more than 10 seconds. Urine was collected for eight hours and analysed for excreted drug by radioimmunoassay.
Results: Sodium cromoglicate is absorbed by the respiratory epithelium, and undergoes renal (43%) and hepatic (57%) excretion. A mean of 0.43% of the total nebulised drug dose was excreted in the urine of the non-distressed infants compared with 0.11% of total dose in the distressed infants. Flow through the small airways was significantly reduced in infants with chronic lung disease of prematurity. Maximum flow at functional residual capacity did not correlate with the amount of drug in the urine, but the degree of distress did.
Conclusion: To maximise absorption, nebulised drugs should be given to settled infants. The degree of airways disease does not influence drug absorption in this age group.