Is there a difference between Methyl nicotinate and Menthyl nicotinate? Are they the same thing? Do they have the same properties?

They are completely different substances, with completely different molecular structures:

metil nicotinato

Methyl nicotinate

mentil nicotinato

Menthyl nicotinate

Methyl nicotinate is a very strong vasodilating agent and can be in some cases highly irritating to the skin even at very low concentrations (0.1% or less). Menthyl nicotinate (Nicomenthyl) effectively enhances skin microcirculation without causing bothersome hyperemia or irritations, on the contrary it generates a pleasant hot-cold sensation in the area of application.