I agree with Karolina. Also, only since this is how it was phrased in your question, if you wanted to say it in the "passive" voice, (what happened to him vs. what he did) then you could say: "They started him on antibiotics." "They put him on an antibiotic."

From a Health Policy or clinical perspective we often say: 1. He was given a regimen of antibiotics 2. She was started on a regimen of antibiotics 3. He was started on antibiotics 4. Antibiotics were administered as a therapy for _____ (the patient) 1. clinical 2. clinical 3. colloquial 4. academic

He began to use antibiotics/ He started using antibiotics. Commence, in general, is quite a fancy word. You would usually use it in a formal meeting by saying: "This meeting will commence immediately.'' :)

I did a check: we DO use "he/she was commenced on antibiotics", but you would only hear this from doctors talking to other doctors, or from medical researchers. It's quite an academic expression. I agree with the other members - it's more natural to say "he was started on antibiotics" or "he started using antibiotics", and so on.