Matrix type transdermal patches of captopril: Ex vivo permeation studies through excised rat skin

Background/objectives

Captopril, "an ACE inhibitor" has comparatively short elimination half life and its oxidation rate in dermal homogenate is significantly lower than that in intestinal homogenate. So as to enhance the bioavailability and to reduce the difficulties associated with captopril, it is decided to design a transdermal drug delivery system for this drug. So the objective of this present work is to formulate and evaluate the matrix type transdermal drug delivery systems of captopril, with different polymer combinations and penetration enhancers.

Methods

Eight formulations (F1–F8) were prepared by the solvent casting technique using varying proportions of polymers such as hydroxypropyl methylcellulose (HPMC), polyethylene glycol (PEG) 400, along with the permeation enhancers such as menthol and aloe vera at different concentrations.

Results

The FTIR results showed no abnormal peaks and thus concluded that no incompatibility between the drug and polymers. The skin irritation studies were performed on rabbits, the results showed no noticeable skin reactions, pointed out the compatibility of drug as well as polymer matrix with the skin. The uniformity of drug content was evidenced by low standard deviation (S.D) values. High folding endurance (>280) revealed that the prepared films have good flexibility. The weight of patches were uniform and thickness varied from 0.05 to 0.13 mm. Ex vivo permeation studies through excised rat skin were carried out using modified Franz diffusion cell, and the results showed that film (F6) containing HPMC and PEG 400 (1:1) with menthol as a permeation enhancer demonstrated the highest drug permeation (90.04%) at 24 h (p < 0.05) with the transdermal flux of 54.5 μg/cm²/h.

Conclusions

The formulation coded as F6 was found to be the ideal patch, shown the maximum drug permeation of 90.04% at the end of 24 h followed Higuchi diffusion kinetics.