Evaluation of transdermal drug-delivery system of capsaicin

Capsaicin has been employed topically to treat many diseases such as rheumatoid arthritis and nerve pain in diabetes. The short half-life of capsaicin by intravenous administration made topical application of capsaicin advantageous.

In this study, we have evaluated differences in the dissolution characteristics of capsaicin patch purchased from market, at different dissolution rotation speed.

The dissolution study was conducted using USP apparatus 5 (n = 6), ERWEKA DT800 dissolution tester and 500 mL of pH 7.4 phosphate buffer as dissolution media. All dissolution studies were carried out at 32 ± 0.5⁰C and different rotation speed (50 ± 5; 100 ± 5 and 150 ± 5 rpm). 5 ml aliquots of samples were withdrawn at various time intervals (1, 4, 8 and 12 hours). Withdrawn were appropriate diluted and analyzed by HPLC.

The HPLC method proposed by Al Othman et al. (2011) has been optimized and validated for the separation and quantitation of capsaicin in a transdermal patch [1].

HPLC analysis was performed using ProntoSIL 120 – 3-C18AQ 125 × 4,0 mm (3 µm) column maintained at 60⁰C. The mobile phase consisted of acetonitrile: water (50:50v/v), the flow rate of 0.9 mL/min, the injection volume 10µL and the detection wavelength 222nm.

The used HPLC method can be applied for fast (total run time was 4.0 minutes) and simultaneous analysis of capsaicin and dihydrocapsaicin in a transdermal patch.

We can conclude that the relative difference of dissolution rate of capsaicin after 12 hours was elevated by increase of dissolution rotation speed (100 rpm vs. 50 rpm: 87.1 ± 12.1% and 150 rpm vs. 100 rpm: 39.6 ± 8.7%).

USP Apparatus 5 could be considered as a discriminatory test that would be able to point out the differences in the dissolution rate of capsaicin at different rotation speed.

[1] Al Othman ZA et al. Molecules 2011; 16:8919 – 8929.