Measurement and prediction of drug solvent losses by evaporation from a jet nebuliser

The evaporative losses of solvent (water) from a commercial jet nebuliser (Unineb, Unimed Ltd) were estimated and found to be approximately 14% of total nebuliser output. A simple analysis of the nebulisation process then enabled the amount of the drug colomycin released as potentially respirable aerosol to be predicted from measurements of the total nebulisation time. Good agreement was found between the predicted (P) and measured (M) values such that P = 1.07 M (r2 = 0.98). The analysis also indicates that the proportion of the drug released as aerosol will increase as nebulisation proceeds provided nebuliser output is continuous and that for a given initial mass of drug a larger amount of drug is released as an aerosol if the volume of administration used in the nebuliser is as large as possible.