Upvote:2
There are no guarantees: that being said, if the pills have no "recreational" value (potential for drug-abuse), then you have less to worry about. I would ensure that your all medication is in properly labeled, preferably by the pharmacy or other authority. The PRC has a very strict policy regarding importation of recreational drugs: I would ensure that any pain medication is properly labeled or just leave it home. Talk to your employer about your concerns and ask for advice from your work peers that have visited China. The Chinese, on the whole, are very reasonable and practical people: especially if they perceive you are cooperative and respectful (which seems to be the case here).
If your medications were only immunno-suppresants and were properly labelled, I would not expect any problems. Given the history with the Opium wars, I would be very aware that they do not take kindly to foreigners bring in additive pills without proper labeling and cause.
Why not type your doctor's note into Google translate and provide a Chinese version? In the unlikely event you a medical emergency, it would be in your interest to have a document with your pills that outlines the pills you require.