There are now luggage locks available that are TSA approved... we've used them going to Mexico and to China (just got back yesterday) without any problems. The locks are combination locks with a key slot on the bottom for the TSA to open if need be. We brought a laptop and kept it locked in one of our bags while touring during the day.

We also kept our vitamins (approx 50-60 pills) in a zip lock bag but we kept 2 packages of sudafed in its original packaging (no box) - our bags were never searched in and out of the US and China. For meds I think it's just safer to keep them in the original vials just in case of an emergency not for yourself but for your travelling companion or for whoever's tending to you. ditto for a list of meds with dosage and doctors' phone numbers.

Have a good trip...!