I was taking vicodin 5-550 for a torn meniscus. Now I have 5-325 and it is not working. Why?

Add adjuvant agent. In some patients, the use of an opioid drug alone may cause intolerable side effects or provide inadequate pain relief. To avoid this problem, the use of adjuvant (co-analgesic) nonopioid agents along with an opioid is encouraged to reduce the amount of the single opioid needed. Examples are oral corticosteroids, tricyclic antidepressants, anticonvulsants, and skeletal muscle relaxants.
Not sure. Seems like little difference between the two doses, but it is possible that you might need to increase the dose a bit. The other possibility is that you have irritated your injury a little bit more therefore it requires a bit more med.