Nifedipine in semi-solid formulations for topical use in peripheral vascular disease: preparation, characterization, and permeation assay

Nifedipine (NFD) has been used for the treatment of cutaneous lesions caused by peripheral vascular disease and diabetic ulcers. NFD was formulated at 8% in three semi-solid formulations: Polaxamer 407 Lecithin Organogel (PLO), PLO plus Transcutol (R), and an oil-in-water (o/w) emulsion. In vitro release and permeation tests were carried out using a synthetic (cellulose acetate) or natural membrane (pig ear skin), respectively, mounted in a Franz-type diffusion cell at 37 degrees C in a constant water bath. As a receptor solution, isotonic phosphate buffer at pH 7.4 was used. All samples were analyzed by high-performance liquid chromatography by employing a previously validated method. The drug flow values were 6.126 +/- 0.288, 4.030 +/- 0.081, and 6.660 +/- 0.254 mu g/cm(2)/h for PLO, PLO plus Transcutol (R), and o/w emulsion, respectively. The three formulations did not show significant differences in drug flow, considering p > 0.05. Furthermore, their penetration profiles in both the epidermis and dermis were statistically different. Thus, the incorporation of NFD in PLO, PLO plus Transcutol (R), and o/w emulsion changed the drug thermodynamic activity, as expected. In addition, Transcutol (R) increased the solubility of NFD in the formulation and promoted its penetration in both the epidermis and dermis.