In any medicines (regardless of the country of their manufacture), the name of the active substance is always indicated in Latin . Therefore, even assuming that border guards at the airport of the Dominican Republic suspect that these medicines may be drugs, it will be necessary to invite a local medical specialist directly from the airport (since border guards are not pharmacists) - and ask this medical specialist read the inscription in the Latin for the border guards . Although, I think that in fact - everything is much simpler: the border guards, most likely, and so there is a list with the names of the active substances of medicines containing narcotic substances, so the medic , most likely, you do not have to call .

As far as I know, diabetes and drugs containing narcotic components are two things that are not related to each other.

No help, sooner everything will not be needed, although their presence would not disturb anyone lo. In any case, the certificate should be written not in Russian (ideally - in Spanish, but also English, and at worst, Latin will also go - this is the "universal" language of all doctors in the world).