Development of an aerosol dosage form containing insulin

An aerosol dosage form containing insulin was developed by suspending insulin zinc crystals in fluorocarbon propellant and using oleyl alcohol to improve the insulin suspension and to prevent valve clogging. A metered valve was used to control the amount of insulin delivered per actuation. The dose dispensed, sedimentation rate, and particle-size distribution of the aerosol formulation were evaluated. The potency of the insulin delivered from the aerosol containers stored at various temperatures and time intervals was determined using a radioimmunoassay. Based upon preliminary stability data, which were treated kinetically, it was noted that insulin aerosols stored in a refrigerator at 7 degrees would have a predicted shelflife of approximately 19 years, whereas samples stored at 25 and 37 degrees would have shelflives of 11 and 2 months, respectively. Long-term stability studies are indicated to establish this conclusion. On the basis of this study, it was concluded that an insulin-containing aerosol dosage form can be formulated and that a suitable dose of insulin can be dispensed using commercially available metered dose valves. The actual dose of insulin dispensed would have to be related to the degree of absorption of insulin one would normally expect when insulin is administered by the inhalation route.