I am on truvada (emtricitabine and tenofovir) and aluvia for pep 28 days. i have a sore back on an unrelated issue, can i take celebrex while on this treatment for pep, thaks?

Yes: Celebrex (celecoxib) is metabolized by a different liver enzyme than ritonavir. You should be fine.

Medications together: Yes. You can take Celebrex or the other anti-inflammatories such as advil and aleve. Just be careful not to overdo it because truvada (emtricitabine and tenofovir) is also hard on the kidneys or can be. Glad to hear you got access to pep.