Model for the Analysis of Membrane-Type Dissolution Tests for Inhaled Drugs

Impactor-type
dose deposition is a common prerequisite for dissolution
testing of inhaled medicines, and drug release typically takes place
through a membrane. The purpose of this work is to develop a mechanistic
model for such combined dissolution and release processes, focusing
on a drug that initially is present in solid form. Our starting points
are the Noyes–Whitney (or Nernst–Brunner) equation and
Fick’s law. A detailed mechanistic analysis of the drug release
process is provided, and approximate closed-form expressions for the
amount of the drug that remains in solid form and the amount of the
drug that has been released are derived. Comparisons with numerical
data demonstrated the accuracy of the approximate expressions. Comparisons
with experimental release data from literature demonstrated that the
model can be used to establish rate-controlling release mechanisms.
In conclusion, the model constitutes a valuable tool for the analysis
of in vitro dissolution data for inhaled drugs.