More glove compartment research

The other glove compartment project we are working on involves a pill box like the one shown below, except that each compartment contains not only ibuprofen pills but also a couple of aspirin pills. This idea came from my mother-in-law, Leslie, who was telling me about someone she knows who keeps all of their medications in one container. I am sure this is pretty common for people who carry around multiple types of medicine.

The chemical name for aspirin is acetylsalicylic acid. When it degrades, the major product is a similar molecule called salicylic acid. (It also relieves pain, but not as effectively. Hippocrates wrote in the 5 B.C. about chewing willow bark for its therapeutic properties - that is a source of salicylic acid). When aspirin breaks down into salicylic acid, it also releases acetic acid. Acetic acid is what makes vinegar smell like vinegar. So, if you have ever opened a bottle of aspirin and smelled vinegar, that is why. Here's the reaction:



So, why are we putting aspirin and ibuprofen together in the glove compartment? We are wondering if the acetic acid released from the aspirin will cause some accelerated degradation of our ibuprofen. That is, if ibuprofen degrades in the glove compartment due to high temperature, will it degrade even more if there it is exposed to acetic acid at the same time?

If you have any other ideas on medicines that people might carry around in the same container, let us know! Aspirin is a good one because we know that the acetic acid is formed and emitted by the tablets.

If you have any old vinegary aspirin in your medicine cabinet, feel free to send it to us! It's a great example of drug degradation for the students, because you can actually smell it - you don't need a complicated chemical analysis to detect the presence of acetic acid.