My doctor has put me on a second round of vancomycin oral capsules for sinus mrsa. he insists it will work. should i keep taking them? (on week 3)

No: Oral vancomycin is not absorbed and is only used to treat clostridium difficile colitis. Mrsa sinusitis should be treated with Minocycline or bactrim/septra which have good activity vs MRSA and get high levels in nasal secretions. I also use Bactroban Nasal ointment to help eliminate nasal colonization. Oral vancomycin is an inappropriate treatment for any sinusitis. Get a second opinion.