AFAIK there is no such an world wide standard, however there is an EU regulation. From www.europe.eu:
A prescription delivered by a doctor in your country is valid in all EU countries. However, medicine prescribed in one country might not be available in another, or it may bear another name.
As of 25 October 2013 you are able to ask for a cross-border prescription which is intended for use in another EU country: these are designed to help the pharmacist understand the prescription easily, the ingredients of the medicine and their dosage.
It's possible a cross-border prescription to be accepted somewhere else too, but there is no guarantee.