Investigations on the viscoelastic performance of pressure sensitive adhesives in drug-in-adhesive type transdermal films

Purpose We aimed to investigate the effect of solubility parameter and drug concentration on the rheological behaviour of drug-in-adhesive films intended for transdermal application. Methods Films were prepared over a range of drug concentrations (5%, 10% and 20% w/w) using ibuprofen, benzoic acid, nicotinic acid and lidocaine as model drugs in acrylic (Duro-Tak 87-4287 and Duro-Tak 87900A) or silicone (Bio-PSA 7-4301 and Bio-PSA 7-4302) pressure sensitive adhesives (PSAs). Saturation status of films was determined using light microscopy. Viscoelastic parameters were measured in rheology tests at 32°C. Results Subsaturated films had lower viscoelastic moduli whereas saturated films had higher moduli than the placebo films and/or a concentration-dependent increase in their modulus. Saturation concentration of each drug in the films was reflected by decreasing/increasing viscoelastic patterns. The viscoelastic windows (VWs) of the adhesive and drug-in-adhesive films clearly depicted the effect of solubility parameter differences, molar concentration of drug in the adhesive film and differences in PSA chemistry. Conclusions Drug solubility parameters and molar drug concentrations have an impact on rheological patterns and thus on the adhesive performance of tested pressure sensitive adhesives intended for use in transdermal drug delivery systems. Use of the Flory equation in its limiting form was appropriate to predict drug solubility in the tested formulations

Surface distribution and depths profiling of particulate organic UV absorbers by Raman imaging and tape stripping

Tape stripping in conjunction with scanning Raman microscopy was used for assessing the lateral and vertical distribution of an organic particulate UV filter, methylene bis-benzotriazolyl tetramethylbutylphenol (MBBT), in a sunscreen formulation. On the volar forearms of three volunteers, 1 mg cm(-2) formulation containing 10% MBBT was applied, and the average amount of MBBT was measured by Raman scanning microscopy in 15 consecutive tape strippings. The recovery of MBBT was 91.1% with 30.2% localizing on the skin surface (first strip), 42.5% in the upper stratum corneum (strips 2-5) and from 3.6 down to 0.8% in each of the 10 consecutive layers. The concentration of surface deposits of MBBT differed by a factor of 300 between folds, furrows and pores on the one hand and the interjacent ridges on the other hand. Seventy-five per cent of the applied particles occupied a fifth of the evaluated area - where concentrating in folds and furrows - as was confirmed by 3-D reconstruction. On interjacent ridges, 8.6% of MBBT distributed as very thin films preferentially. MBBT localized at sites not connected with the surface, such as in truncated pores or as potentially penetrated material amounted to 0.06% or to a twentieth of the 1.4% found in the lowest skin strippings. Scanning Raman microscopy in combination with tape stripping documented the lateral and vertical distribution quantitatively and at cellular (12.5 ?m) lateral resolution. Our results confirmed an earlier report on the vertical distribution of organic particles applied to skin and was in line with similar reports on TiO(2) distribution

Surface tension and wettability in transdermal delivery: A study on the in-vitro permeation of haloperidol with cyclodextrin across human epidermis

10.1211/jpp.62.06.0014Journal of Pharmacy and Pharmacology626770-778JPPM