Effect of Chemical Enhancers on in Vitro Release of Salbutamol Sulphate from Transdermal Patches

The effect of combination of PG with DMSO, BC, IPM, Tween 80 and SLS on drug release rate was studied in vitro. The mechanism of drug release was also studied by using power law. Significant difference (One way ANOVA; p<0.05) in release rate among the 16 formulations was seen in the study. The release profiles of various formulations also showed that the added enhancers in individual batches affect the release rate of the drug. The concentration of DMSO and Tween 80 showed directly proportional where as concentration of BC and SLS showed inversely proportional relationship with drug release rate. The increase followed by decrease in drug release rate was seen with increase in IPM concentration. In most of the formulations, drug release occurred by diffusion partially through a swollen matrix and water-filled pores. INTRODUCTION A transdermal drug delivery is a formulation or device that maintains the blood concentration of the drug within the therapeutic window ensuring that drug levels neither fall below the minimum effective concentration nor exceed the minimum toxic dose [1]. Transdermal delivery of drugs promises many advantages over oral or intravenous administration, such as a better control of blood levels, a reduced incidence of systemic toxicity, an absence of hepatic first-pass metabolism, etc [2]. However, drugs should possess several physico-chemical prerequisites such as shorter half-life, small molecular size, low dose etc to be a suitable candidate for transdermal drug delivery system (TDDS) due to formidable barrier action of keratinized cells present in stratum corneum (SC) of skin. In order to permeate and absorb sufficient amount of drug to show the therapeutic effect, permeation should be enhanced. Many approaches such as use of chemical, physical, chemical-chemical, chemical-physical and physical-physical enhancers have been applied for permeation enhancement of drugs [3]. Chemical enhancers partition into and interact with the SC constituents to induce a temporary, reversible increase in skin permeability where as physical enhancers induce the skin permeability by using physical forces such as magnetic field, electric current, vibration etc. Combination of chemicalchemical, chemicalphysical and physical-physical enhancers had been shown the synergistic effect in the permeation enhancement. However, it had been suggested that it would be better to choose the combination that works in a natural way (combination having different mechanisms of permeation enhancement) in order to obtain greater enhancement and to prevent the permanent and irreversible disruption in the skin [3]. Besides the natural combination, S. Mitragotri suggested controlling the amount of