Iontophoretic Transport of Model Compounds from a Gel Matrix Across a Cellophane Membrane

Improved Skin Penetration Using In Situ Nanoparticulate Diclofenac Diethylamine in Hydrogel Systems: In Vitro and In Vivo Studies

Delivering diclofenac diethylamine transdermally by means of a hydrogel is an approach to reduce or avoid systemic toxicity of the drug while providing local action for a prolonged period. In the present investigation, a process was developed to produce nanosize particles (about 10 nm) of diclofenac diethylamine in situ during the development of hydrogel, using simple mixing technique. Hydrogel was developed with polyvinyl alcohol (PVA) (5.8% w/w) and carbopol 71G (1.5% w/w). The formulations were evaluated on the basis of field emission scanning electron microscopy, texture analysis, and the assessment of various physiochemical properties. Viscosity (163-165 cps for hydrogel containing microsize drug particles and 171-173 cps for hydrogel containing nanosize drug particles, respectively) and swelling index (varied between 0.62 and 0.68) data favor the hydrogels for satisfactory topical applications. The measured hardness of the different hydrogels was uniform indicating a uniform spreadability. Data of in vitro skin (cadaver) permeation for 10 h showed that the enhancement ratios of the flux of the formulation containing nanosize drug (without the permeation enhancer) were 9.72 and 1.30 compared to the formulation containing microsized drug and the marketed formulations, respectively. In vivo plasma level of the drug increased predominantly for the hydrogel containing nanosize drug-clusters. The study depicts a simple technique for preparing hydrogel containing nanosize diclofenac diethylamine particles in situ, which can be commercially viable. The study also shows the advantage of the experimental transdermal hydrogel with nanosize drug particles over the hydrogel with microsize drug particles.

Iontophoretic and chemical enhancement of drug delivery. Part I: across artificial membranes

This paper reports on measurements of the release characteristics of the model drug salbutamol base from a liquid crystalline vehicle across a non-rate limiting synthetic membrane. The measured passive release rates were compared with analogous behaviour: (i) when a penetration enhancer such as oleic acid was incorporated into the vehicle; (ii) when the release was iontophoretically assisted; and (iii) when the penetration enhancer and iontophoretic assistance were used simultaneously. The effects of using isotonic phosphate buffer solution as the aqueous domain of the vehicle and in the receptor were also separately assessed. The passive release from the standard system was consistent with matrix diffusion control. The addition of oleic acid indicated association of the drug with the fatty acid so that its release into an aqueous medium was significantly retarded. With buffer ions present in the vehicle the release rate increased consistent with reduced association, and when phosphate buffer was used as a receptor medium the release rate exceeded that of the standard vehicle due to an ion exchange process. The delivery of salbutamol from the fatty acid containing systems was substantially enhanced by iontophoresis and the rates were shown to be approximately proportional to the assisting currents. The data clearly indicate the iontophoretic process to be significantly less efficient in the presence of buffer ions but with the iontophoretic delivery rates being enhanced by the presence of a fatty acid.

Properties of transdermal histamine iontophoresis: differential effects of season, gender, and body region

Histamine iontophoresis is demonstrated to be a reliable model for the study of inflammatory skin responses. It has the advantage of a non-invasive and uniform mode of application and is free of unwanted side effects. The wheal and flare responses to histamine are linearly related to dose over a wide range of stimulus strengths (r = 0.88). In summer, wheal responses were smaller, probably due to increased thickness of the epidermis. Female subjects generally expressed larger wheal responses than males, presumably due to differences in epidermal thickness and structure. There were significant regional differences in wheal, flare, and laser Doppler recorded flux responses. Ratings of itch sensations also showed clear, but less pronounced, differences of body regions. Significant regional differences of wheal and flare responses existed. Sensory discrimination of different stimulus levels was demonstrated with visual analogue scale ratings.

In vitro iontophoretic studies using a synthetic membrane

In vitro iontophoretic administration of drugs through a microporous polyolefin membrane with hydrophilic urethane polymerfilled pores was done for the ionized drugs dexamethasone sodium phosphate, hydrocortisone sodium phosphate, and prednisolone sodium succinate, and for a nonionizable drug cortisone acetate. Currents between 0.2 and 0.8 mA were demonstrated to be effective in increasing the transmembrane transport rate compared with passive diffusion for all the ionizable drugs studied. However, these currents failed to show any significant effect on the transmembrane transport rate of the nonionizable drug, cortisone acetate. There was a good linear relationship between the applied current (I, mA) and the transmembrane transport rate (J, micrograms/mL) in the receptor cell for all the ionized drugs (J = 1.97I + 0.70 for dexamethasone sodium phosphate; J = 2.05I + 1.49 for hydrocortisone sodium succinate; J = 2.25I + 1.93 for prednisolone sodium succinate). This in vitro iontophoretic study demonstrated that electric fields interact more efficiently with charged than with uncharged molecules.