Dear Christopher Cat
Is it safe to freeze leftover medications?
Usually not. But before we get to that, let me address leftover medications in general.
Mom always makes me finish a course of drug therapy, even if I feel better before the medication is gone. If your veterinarian recommends the same for your pet, you should have no leftover medications.
However, if you do, freezing might diminish their potency.
Manufacturers test the stability of their products when stored as recommended, usually at room temperature. So even I, an unusually smart cat, don’t know for certain how freezing will affect each medication.
Freezing might prolong the stability of some drugs. However, ice crystals that form in household freezers are known to degrade drugs.
Liquid medications in suspension or emulsion cannot withstand freezing.
Moreover, repeated freezing and thawing damages medications, and capsules often stick together as they thaw.
If you have leftover medications, talk with your veterinarian or pharmacist about storage.