On behalf of a Stabilitarian- How would one conduct an “in use” study on drug product capsules in blister packs that would simulate patient use (other than what is normally conducted under routine stability conditions)? There doesn’t seem to be any literature on this scenario.
In-use usually focuses on the product remaining in a bottle, having been exposed to more oxygen and moisture due to opening (and product jostling). I haven’t heard of a blister pack in-use study as yet, but it’s not unfathomable that a regulatory inspector could raise the issue.
One response would be to explain that you do not conduct in-use for that package type with a strong justification that remaining product does not experience “exposure”.
A second response would be to design an in-use study that assumes removing the blister pack from secondary packaging represents a challenge to the product (heat/humidity/light exposure potentials?) Additionally, if there is any possibility that pulling back the lidding on one pack could inadvertently damage the seal on a connected blister, that could be a basis for observation and evaluation. Some readers may be able to share further scenarios to test.