I am a Stage 4 M1b prostate cancer patient who has been under treatment at MD Anderson for the last 3 years. In March, I had a root canal and was prescribed 10 days of the antibiotic clendamycin. My PSA decreased over the next 3 months to one-half the value that it was before. Then it returned to what it had been. Anyone else experience something similar after taking either clendamycin (or another member of the erythromycin family) or doxycycline (or another member of the tetracycline family)? For anyone who did, what was the reaction of your oncologist to this?