No knowledge about the specific drugs you mention but most medications are available (no prescription needed) at the pharmacy on Rama 4 --CHULA BESAJ -- a short walk from Dusit Thani Hotel on Rama 4.
Prices always cheaper than normal pharmacies.
Make sure you get the right shop as there are several pharmacies in that strip of Rama 4.
Their phone no. is 02 235 3133-4 mobile 085 522 5959
LINEID: chulabhesaj
Open mon-sat 8:30 am -8:00 pm
Tip for any pharmacist write the names of your medicines on paper or photograph on your mobile.