As far as I know, there is not such a world-wide standard, however there is an EU regulation. From [www.europe.eu][1]:

> 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 may be accepted somewhere else too, but there is no guarantee.

  [1]: http://europa.eu/youreurope/citizens/health/help-from-the-pharmacy/prescription/index_en.htm