Inhalation of tobramycin in cystic fibrosis - Part 1: The choice of a nebulizer

Forteen commercially available jet and ultrasonic nebulizers were investiga ted with the aim to select the most suitable type of apparatus for the inha lation of a 10% tobramycin solution. Two different techniques for measureme nt of particle size distribution were evaluated: laser diffraction and casc ade impactor analysis. The final selection of the nebulizers is based on pa rticle size distribution, output and stable performance during nebulization . All 14 nebulizers (eight jet and six ultrasonic) were filled with a solut ion of 10% m/v tobramycin (as sulphate) in water. The volume in the tested devices ranged from 4.5 to 10 ml (=450-1000 mg tobramycin) in accordance wi th the prescribed usage by the suppliers. The nebulizers were connected wit h a special designed adapter to a laser diffraction analyser in order to me asure particle size distribution of the aerosol. Inhalation was simulated w ith a static flow of 40 l/min. The particle size distribution (expressed as X-10, X-50, and X-90) was determined after 10 s, 1.5, 3, 4.5, 6, 9 and 12 min of nebulization. Furthermore, the tobramycin solutions were assayed for tobramycin content before and after nebulization. For all nebulizers, the mean particle size distribution, depicted as X-50, was within the range of 1-5 mm. There were no relevant differences between the nebulizers in concen tration or particle size distribution during nebulization. The output of th e nebulizers is a result of both nebulization and evaporation. The output, expressed as volume of tobramycin solution, ranged from 0.06 to 0.50 ml/min . The output of tobramycin ranged from 1.2 to 39.5 mg/min. For clinical pra ctice 300-600 mg have to be nebulized within 20-30 min. Lt was concluded th at only three jet nebulizers [Porta-Neb Sidestream (PNS), Porta-Neb Ventstr eam (PNV) and Pariboy Pari LC + (PLC)] have a reasonable output and an acce ptable particle size distribution for the administration of a 10% tobramyci n solution in the therapeutic dosage range. (C) 1999 Elsevier Science B.V. All rights reserved.