CHARACTERIZATION OF TRANSDERMAL DELIVERY OF NEFOPAM HYDROCHLORIDE UNDER IONTOPHORESIS

In vitro iontophoretic delivery of nefopam hydrochloride was conducted to study the effects initial drug concentration, pH, ionic strength a nd viscosity of the donor solutions on the transdermal flux through a hairless mouse skin. Stability of nefopam hydrochloride under the expe rimental conditions was investigated. Type of electrode, current inten sity, electric voltage and electrode distance were evaluated. Appropri ate conditions were selected to minimize the potential degradation pro blems of nefopam hydrochloride during iontophoresis. Results show that the silver/silver chloride electrode provides better drug stability t han the platinum electrode. Higher current intensity resulted in faste r transdermal flux and therefore better drug permeability. The increas e in the drug permeability appears to be proportionally increased as t he current intensity increases in the range of 0.253 to 1.265 mA/cm(2) . The iontophoretic transdermal delivery of nefopam hydrochloride was observed to increase as the drug concentration in the donor site was i ncreased until it's close to the equilibrium concentration. The optimu m pH to achieve the best iontophoresis under constant current was dete rmined to be at pH 3.0. This may be due to the highest available charg e density of nefopam was achieved at this pH to provide the best condu ctance. A decrease in the iontophoretic transdermal flux was encounter ed as an increase in the solution ionic strength due to the increased competition of similar charged ions with the available current. The in crease in the donor solution viscosity decreased the conductivity of t he ions and hindered the transdermal flux of the drug under iontophore sis.