Before taking penicillin V, tell your doctor if you are using any of the following drugs:
methotrexate (Rheumatrex, Trexall); or
probenecid (Benemid).
This list is not complete and there may be other drugs that can interact with penicillin V. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.
 Penicillin v potassium drug interactions (more detail)
