Thanks for the query.
As such there is no specific code to write a particular medicine
We only write R or Rx in the beginning of our prescription and this is followed by the name of drug and the way it has to given.For example if you have to give XANAX
then prescription would look like
Tab. XANAX 2 mg 1 tab. b.i.d for three days
It means one tablet twice a day for three days.
R simply means a prescription.
Please get back in case you have something more to ask.
Best of luck