As I understand it, only select drugs, i.e. narcotics, require a prescription. Nearly everything else can be purchased without a prescription. Most of the "pharmacies" I saw in Cozumel had a very limited selection of meds available, ******, antihypertensives, hypoglycemics, etc. The prices were substantially lower than prescription prices in the US. Mexico doesn't have the strictest controls over drug manufacturing and importation so buyer beware!