Noninvasive assessments of the percutaneous absorption of methyl nicotinate in humans

Percutaneous penetration of the vasodilator methyl nicotinate (methyl 3‐pyridinecarboxylate) has been monitored in vivo in humans with the noninvasive techniques of laser Doppler velocimetry and photopulse plethysmography. These optical methods use different technologies to generate a voltage output which is related to perfusion of the cutaneous microcirculation. The procedures are therefore sensitive to the pharmacologic stimulus and duration of local vasodilation. Following topical application of methyl nicotinate, excellent correlation was found between the response of both methods and the visual observation of erythema. Lower drug concentrations delayed the onset and magnitude of the response and shortened the time period for which elevated microperfusion was observed. These techniques appear to provide a useful noninvasive assessment of the time course of drug behavior in the region of skin to which topical application is made.