A review on formulation of transdermal patch for controlled release action

Pharmaceutics

The main aim of this study is to review the formulation of transdermal patches using different polymers and permeation enhancers in different ratios to see the release of drug in controlled action and also to check whether the bioavailability is enhanced by the use of permeation enhancers. These transdermal patches were prepared as Matrix diffusion-controlled system. Drug reservoir of homogenous dispersion of drug with hydrophilic or lipophilic polymer is prepared with one of the following methods. Homogenous dispersion of finely ground drug particles with liquid polymer or highly viscous base polymer followed by cross linking of polymer chains OR Homogenous mixing of drug solid with rubbery polymer at an elevated temperature. The main advantage of transdermal patches is that the first pass metabolism is avoided and this also leads to enhancement in the bioavailability. Many drugs are administrated orally, but due to the first pass metabolism in increases the dose and decreases the effects of drug. So, transdermal drug delivery system is design to improve the efficiency and bioavailability of the drug and decreases the number of doses. Transdermal drug delivery system is administrated by skin and drug is delivered directly into systemic circulation maintaining continuous efficacy. These systems provide drug systemically at a predictable rate and maintain the rate for extended period of time thus eliminating numerous problems associated with oral products such as reduced bioavailability, enhanced first pass hepatic metabolism, relatively short residence time, dose dumping and dosing inflexibility Physicochemical point of view, an ideal transdermal drug candidate has to meet a number of requirements such as drug is highly lipophilic in nature, melting point of the drug is above 150, molecular weight is above 500 Dalton, log p values 1-5, no local toxicity and irritation to skin.

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