In vitro comparative studies of two marketed transdermal nicotine delivery systems: Nicopatch and Nicorette

The aim of this work was to compare in vitro the performances at delivering nicotine of two transdermal delivery system (TDS): Nicorette (8.3 mg/10 cm(2) nicotine content) and Nicopatch (17.5 mg/10 cm(2)). Release profiles were obtained using the FDA paddle method, and skin permeation profiles using Franz-type diffusion cells. Using the first method, nicotine release followed the polymer matrix diffusion-controlled process, as suggested by the linear Q versus t(1/2) relationship. Cumulative amounts released from Nicopatch were twice the amounts released from Nicorette, but the released fractions were almost equal for both TDS ( approximately 50%). Using diffusion cells, skin permeation rates were constant over the time: they were not significantly different between both TDS and close to in vivo claimed releases: Nicorette should be considered as more efficient at delivering nicotine through skin than Nicopatch. However, cumulative permeated amounts were overestimated, indicating that the actual diffusion surface area exceeded the effective diffusion surface area of the cells. Reducing the trimmed TDS surface area led not only to a reduction of the cumulative permeated amounts, but also to a reduction of the permeation rates. Therefore, the usefulness of the method to evaluate skin permeation parameters of TDS is questioned.