Effects of adhesive formulations on adherence and release properties of reservoir-type transdermal systems

Elena Zour, University of Rhode Island

Abstract

This study examined in-vitro the effect that adhesive formulations have on the adhesion properties and release characteristics of a reservoir type transdermal system. A series of laminates (CMLs) consisting of the protective liner, the rate-controlling membranes (9% EVA, 12% EVA, or Celgard$\sp{\circler}$) and pressure-sensitive adhesives (based on silicone and polyisobutylene polymers) were prepared. Transdermal systems using these laminates and two types of nitroglycerin reservoirs, were fabricated by a heat sealing method. The adhesion properties of the systems were evaluated using a tensile testing machine (Instron), while their release characteristics were determined using a "paddle-over-disk" dissolution method.^ Systems containing silicone-based adhesives had a higher adhesion strength and higher release profiles of nitroglycerin when compared to the polyisobutylene (PIB) adhesives. Replacement of the 9% EVA membrane with the 12% EVA resulted in no significant change in the adhesion strength of the systems, but a significant increase in the release profiles for all adhesives used. Estimation of the apparent diffusion coefficient of the drug using a NONLIN program, indicated that the permeability coefficient of the systems with 9% EVA was not altered by the adhesive layer; however, there was a significant decrease in the permeability of the 12% EVA membrane, resulting in the adhesive controlling the rate of drug delivery. The addition of more plasticizer (mineral oil) to the PIB adhesive resulted in higher release rates of nitroglycerin from all systems tested, due to the higher "free volume" available and the increased partition coefficient of the drug in the oil. The use of Celgard$\sp{\circler}$ as the rate-controlling membrane, produced a dramatic decrease in the adhesion strength and a significant increase in the release profiles of systems with the silicone adhesives. In contrast, much lower but constant release rates were obtained from systems with Celgard$\sp{\circler}$ and polyisobutylene adhesives, probably because the pores of the membrane were blocked and the mechanism of diffusion altered. Transdermal systems that contained isopropyl alcohol in their reservoir, had very low adhesion strengths due to the similar solubility parameters of the solvent and the adhesives. Systems with isopropyl alcohol showed a higher initial nitroglycerin flux, but the total amount of drug released in 24 hours was approximately the same for both reservoir formulations. ^

Subject Area

Health Sciences, Pharmacy

Recommended Citation

Elena Zour, "Effects of adhesive formulations on adherence and release properties of reservoir-type transdermal systems" (1987). Dissertations and Master's Theses (Campus Access). Paper AAI8811574.
http://digitalcommons.uri.edu/dissertations/AAI8811574

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