BEHAVIOR OF NEBULIZING SOLUTIONS AND SUSPENSIONS

A compressed air source is needed to run a jet nebulizer, its operatin g pressure affects the aerosol flow through the nebulizer, the quantit y of drug and/or solution leaving the nebulizer, and the droplet size. With increasing pressure, the output (gravimetric change during nebul ization) will increase and the droplet size decrease. The temperature of the nebulizing solution will decrease by as much as 10-degrees-C du e to energy loss from evaporation of droplets. Other important conside rations in nebulizer therapy are taste, pH and viscosity of the soluti on. For those drugs which cannot be dissolved, the nebulizing behavior is different. In nebulizing suspensions, the drug particles must be m icronized to a mass median diameter of 1-2mum to give optimal output c onditions from jet nebulizers with a droplet size of 3mum mass median diameter. The solid drug particles leave the nebulizer through the med ium of the droplets, and when a solid drug particle is larger than the droplet it will become trapped in the nebulizer. This has been illust rated in a separate experiment in which 0.5mg/ml budesonide was nebuli zed from eight different nebulizers. The droplet size as well as the o utput - calculated from the quantity of drug remaining in the nebulize r after 10 min nebulization - varied with type of nebulizer. A prefera ble way of determining drug delivery to a patient is to collect the ae rosol on a filter during normal breathing and then analyse the drug co ntent on the filter. Output characteristics can only be used for funct ional testing of nebulizers and in comparisons of different brands of nebulizers.