Effect of Mild Hyperthermia on Transdermal Absorption of Nicotine from Patches.

Application of heat (hyperthermic conditions) on skin is known to enhance drug transfer and facilitate skin penetration of molecules. The aim of this work was to study the effect of hyperthermia on the drug release and skin permeation from nicotine transdermal patches. The drug release and skin permeation were characterized by in vitro release test and in vitro permeation test. The temperature was maintained at 32 °C as control (simulating normal physiological skin temperature) and 42 °C as hyperthermia condition. The in vitro release test was carried out using USP apparatus 5-Paddle over disk method for a transdermal patch. Skin permeation study was carried out across porcine skin using the flow through cells (PermeGear, Inc.) with an active diffusion area of 0.94 cm². Mechanistic studies (parameters such as partition coefficient, TEWL and electrical resistivity) were also performed to understand the mechanisms involved in determining the influence of hyperthermia on drug delivery from transdermal patches of nicotine. The rate and extent of drug release from nicotine patch was not significantly different at two temperatures (Cumulative release after 12 h was 43.99 ± 3.29% at 32 °C and 53.70 ± 5.14% at 42 °C). Whereas, in case of in vitro permeation studies, the nicotine transdermal permeation flux for patch was threefold higher at 42 °C (100.1 ± 14.83 μg/cm²/h) than at 32 °C (33.3 ± 14.83 μg/cm²/h). The mechanistic studies revealed that the predominant mechanism of enhancement of drug permeation by hyperthermia condition is by the way of increasing the skin permeability. There is a potential concern of dumping of higher dose of nicotine via transdermal route.