Radiolabelling of Beclomethasone Dipropionate

Little is known about delivery of aerosolised steroids to neonatal patients undergoing assisted positive pressure ventilation and after extubation. A rabbit model has been established to investigate factors influencing drug delivery. Beclomethasone dipropionate, in a metered dose inhaler, was radiolabelied with technetium 99m. The mass median aerodynamic diameter of the aerosol was 3-3 (2.0) pm and the impactor measurements confirmed that the technetium distribution corresponded with that of the drug particles. The metered dose inhaler was actuated into a coliapsible spacer that was used to ventilate and deliver aerosol to anaesthetised rabbits by a tracheostomy. From each actuation of the drug 2.9 (0-4)% of the aerosol deposited in the trachea and main bronchi and 1-2 (0-4)% in the lung. When the drug was delivered by a spacer device, with facemask attachment, to rabbits breathing freely through a tracheostomy, aerosol deposition increased to 4-4 (2-1)% in the trachea and main bronchi and 1-9 (0.9)% in the lung lobes. The maximum change in systolic blood pressure after administration of aerosol by the coliapsible spacer was a decrease of 13%. The methods described may prove useful for the delivery of inhaled steroids to neonatal patients likely to develop bronchopulmonary dysplasia. University Hospital, Nottingham, Department of Child Health Christopher O'Callaghan Julie Stammers Terence J Stephenson David Hull Department of Medical Physics John Hardy Correspondence to: Dr Christopher O'Callaghan, Department of Child Health, Leicester Royal Infirmary, Infirmary Square, Leicester LEl 5WW. Accepted 26 July 1991 Oral steroids in the form of dexamethasone have been used with some success in the treatment of bronchopulmonary dysplasia.' 2 However, dexamethasone given over long periods may be associated with significant side effects such as prolonged suppression of the hypothalamicpituitary-adrenal axis.3 Since their introduction, inhaled steroid aerosols have become the mainstay of treatment of asthmatic patients with moderate to severe symptoms, reducing the need for large systemic doses. The considerably smaller dose used for inhalation treatment is associated with few side effects. It is postulated that low doses of inhaled steroid started early in the management of very low birthweight infants requiring ventilation may reduce the severity of bronchopulmonary dysplasia by reducing inflammation and subsequent tissue damage. One ofthe conclusions from a recent workshop on aerosol treatment in the newborn was that technical problems of delivering suspended particles by aerosol need urgent solution in view of clinical demand for topical steroid treatment by aerosol in newborns.4 The aim of this study was to use a rabbit model to assess methods of delivery of aerosolised steroids to the airways. The results of these experiments may lead to improvements in aerosol delivery to neonatal patients.