Development and Evaluation of a Transdermal Patch Containing Thespesia populnea Bark Extract .

Abstract

Background: Transdermal drug delivery is a sustain drug delivery method to treat inflammatory conditions. Thespesia populnea plant has been used in Ayurveda to treat inflammatory conditions. Thus, a transdermal patch was formulated as a convenient method to treat inflammation with this plant. Objective: To develop a transdermal patch containing ethanolic bark extract of T. Populnea Method: The crude ethanolic bark extract was obtained from the Soxhlet extraction. The maximum effective, non-toxic concentration (MEC) was evaluated using Human Red Blood Cell (HRBC) membrane stabilization and brine shrimp toxicity assays. Eleven patch bases (PA1-PA11) were developed by varying ratios of hydroxypropyl methyl cellulose (HPMC) and sodium alginate. Folding endurance, surface pH, thickness and moisture content were evaluated to select the best patch base. The MEC was incorporated to the most stable bases and transdermal patches (TPA) were formulated using solvent casting method. Compatibility between the polymers and the crude extract was investigated using Fourier Transform Infrared (FTIR) spectroscopy. In vitro drug release was evaluated for 8 hours. HRBC assay and the brine shrimp assay were conducted for the released samples collected at define time duration. Skin irritation and different physico chemical properties were evaluated on the TPAs. Results: The MEC was 5 mg/mL. PA1 and PA3 were selected as the best bases according to the physicochemical properties. TPA1 and TPA3 had a thickness of 0.32±0.01 and 0.39±0.01 mm, pH 6.9±0.5 and 7.1±0.5, and weight uniformity of 0.19 and 0.21 g, with a folding endurance >243 and >260, moisture content of 6.31 and 5.71%, respectively. Both patches were reddish-brown, translucent, flexible and slightly smooth with a faint camphoraceous odor. However, TPA1 showed a steady release kinetics over the release period and revealed a maximum inhibition of 58.48 ± 0.42% after 5 hours, whereas TPA3 did not show drug release over the time. TPA1 did not exhibit any in vitro toxicity and no oedema or allergic reactions 24 hours post-application. No phase separation or defects were observed in TPA1 during stability period at room temperature and 45°C. Conclusion: TPA1 was the most stable transdermal patch that can be optimized in future as a commercial product.