Stability of dry powder formulations used in drug delivery to the lungs studied one particle at a time

There is great utility in the use of pharmaceutical drugs delivered via the pulmonary route, due to the possibility of localised administration to the lungs for treatment of respiratory disease, or as an alternative delivery route to reach the systemic circulation rapidly. Localised drug delivery to the lungs typically allows lower dosages to be used when compared to, for example, oral dosage forms (tablets, capsules). This can help maintain drug efficacy but reduce unwanted side effects. In this project the method of administration to the lungs is via the use of a dry powder inhaler (DPI). The advantages of DPIs over other inhaler types include their lack of propellants or other external energy source, ease of use, and their small and portable nature.

Although the use of aerosolised drug delivery is well precedented, DPIs are considered a complex dosage form due to the particulate interactions that can occur within the powder blend and between the powder and inhaler.

The focus of this project is to study the stability trends of pharmaceutical blends for dry powder formulations, particularly the long-term physical stability regarding water absorption. Measurements in response to changes in water vapour concentration (relative humidity) will be made on individual particles using an electrodynamic balance. The project will also look at the physical stability of drug formulations when stored in different conditions for the duration of the proposed product shelf life.