Can a U.S. doctor send a prescription to another country?

Could you elaborate on the feasibility of a U.S. doctor transmitting a prescription to a patient residing in a different country? Are there any legal constraints or regulations that might impede this process? Additionally, what are the potential challenges and considerations that both the doctor and the patient should be aware of when pursuing such an arrangement? How does the process differ from sending a prescription domestically, and what steps might be necessary to ensure the validity and accuracy of the prescription when it crosses international borders?