Which of the following medications must be kept in the refrigerator?

Gabapentin solution must be kept in the refrigerator to ensure its stability and potency over time. The refrigeration helps to slow down the degradation of the medication, which can be more sensitive to temperature changes than solid forms of the drug. Storing gabapentin solution at a controlled cooler temperature protects the integrity of the medication, making it safer and more effective for use in veterinary applications.

In contrast, while medications like methimazole can have specific storage requirements, they typically do not need to be refrigerated. Similarly, ibuprofen and prednisone are also stable at room temperature and do not require refrigeration for proper storage. This knowledge is critical for veterinary medication clerks to maintain appropriate drug efficacy and safety for animal patients.