In vitro study of transdermal nicotine delivery: influence of rate-controlling membranes and adhesives

Development of transdermal system containing nicotine by using sustained release dosage design

This study was carried out to develop a membrane-controlled transdermal formulation (TF) of nicotine by using sustained release dosage design (SRDD). TFs were prepared with polyethylene membrane as a rate-controlling barrier; a carbomer was used as the gel reservoir with or without propylene glycol (PG). The in vitro target flux (0.0535 mg cm(-2) h(-1)) was calculated according to SRDD calculations. Nicotine permeation through the membrane with or without transfer adhesive was also studied using diffusion cells. Nicotine permeated through membrane (without adhesive) with a flux of 0.0555 mg cm(-2) h(-1) and this value was similar to that of the in vitro target flux. The release from the TFs and from a commercial product (Nicotinell, 52.5 mg 30 cm(-2)) was studied using the FDA paddle method. The nicotine amount was increased from 22.7 to 56.5 mg in gel reservoir, and a plateau was reached beyond 45.4 mg of drug; the system attained the maximum thermodynamic activity with 56.5 mg of nicotine. The release rate from TFs (without adhesive layer) containing PG in the reservoir was very similar to the target release rate (1.07 mg h(-1)). The fluxes of nicotine from Nicotinell and TF containing 45.4 mg of nicotine were close to the in vitro target release rate.

Broadband light profile microscopy: a rapid and direct method for thin film depth imaging

Light profile microscopy (LPM) is a recently developed technique of optical inspection that is used to record micrometer scale images of thin film cross-sections on a direct basis. This technique uses a novel right-angle imaging geometry that shows outstanding contrast for subtle interface structures and morphologies that are invisible to conventional methods of inspection. When laser sources are used for sample illumination, image contrast is provided by luminescence and elastic and/or inelastic scatter. When a white-light excitation source is used for LPM, primary contrast is obtained from elastic scatter, while secondary contrast results from refraction, secondary transmission, and secondary reflection from material phases. We term this mode of inspection broadband light profile microscopy (BB-LPM). It is implemented with a compact, easily aligned apparatus and minimal sample preparation, and it shows outstanding interface contrast similar to laser LPM. In this work we demonstrate BB-LPM as a method for direct imaging of the layers structures of a variety of thin film samples of industrial and manufacturing interest.

Shed king cobra and cobra skins as model membranes for in-vitro nicotine permeation studies

Shed king cobra skin (SKCS) and shed cobra skin (SCS) were investigated for use as barrier membranes, including some pre-hydration factors, for in-vitro nicotine permeation. Inter-specimen variations in nicotine fluxes using shed snake skin were compared with those using human epidermis. Nicotine in the form of 1% w/v aqueous buffer solution at pH 5 and transdermal patches (dose 14 mg day(-1)) were used. The nicotine fluxes across the shed snake skin were not significantly affected (P > 0.05) by temperature and duration of hydration pre-treatment. Scanning electron micrographs of SKCS and SCS revealed a remarkable difference in surface morphology, but the nicotine fluxes using both shed skins were not significantly different (P > 0.05). When compared with the results obtained using human epidermis, there were similarities in fluxes and permeation profiles of nicotine. Using nicotine solution, the nicotine permeation profiles of all membranes followed zero order kinetics. The amount of nicotine permeated provided good linearity with the square root of time over 24 h (R(2) > 0.98) when using nicotine patches. The nicotine fluxes using SKCS and SCS had less inter-specimen variation than those using human epidermis. The results suggest a potential use for SKCS or SCS as barrier membranes for in-vitro nicotine permeation studies.

In vitro release study of verapamil hydrochloride through sodium alginate interpenetrating monolithic membranes

Polymeric sodium alginate interpenetrating network membranes containing verapamil hydrochloride were fabricated for transdermal application. The membranes were evaluated for their physical properties, weight and thickness uniformity, water vapor transmission, as well as drug content uniformity. All the thin patches were transparent, smooth, and flexible. The drug-loaded membranes were analyzed by X-ray diffraction to understand the drug polymorphism inside the membrane. The transdermal patches were permeable to water vapor, indicating the permeability characteristics of the polymers. The in vitro drug release was performed in distilled water using a Keshary-Chien diffusion cell. The release data were analyzed to understand the mechanism of drug release.