Flying medicine

you can find many big pharmacies on Hai Ba Trung street, dist 1. just near Tan Dinh market.

I think you can buy it from the leading medical stores.
Try on Hai Ba Trung street or Tran Hung Dao

medical market can be found in Nguyễn Vãn Thanh street, (d10 i think ).

There is a medical clinic on the corner of Pasteur,( down the street from Gammer Beer) and Alexandre Rhodes. Columbia Asia Saigon. They have a 'certified' pharmacy and sell many Western medicines. You might need to see a doc first, though. Everyone speaks English there. Have two Vietnamese doctors on staff and one American. Cost to see Vietnamese doc is $40, American $60. If you need a particular medicine, you can probably get it there. Good luck!