Formulation and evaluation of etodolac lecithin organogel transdermal delivery systems

Objective: Etodolac (ETD) is a non-steroidal anti-inflammatory drug used for the acute and chronic treatment of rheumatoid arthritis. It exhibits poor water solubility so its bioavailability is limited. Long term use of ETD causes serious gastrointestinal disturbance. Lecithin organogels (Los) have generated considerable interest over the years as potential topical drug delivery vehicle. Therefore, the objective of this study was to formulate ETD in lecithin organogels as a transdermal delivery system. Methods: Based on the preliminary studies, pseudoternary phase diagrams were constructed using isopropyl myristate (IPM), water and lecithin as a surfactant with different cosurfactants (CoS) and organogel areas were identified and three systems each of 36 formulae were prepared. A number of organogels were selected and loaded with 1% ETD then evaluated for visual inspection, spreadability, pH, rheological and in vitro release studies to select the optimum formulae. The selected formulae were subjected to ex-vivo permeation through excised abdominal rabbit skin and their stability was studied for one year of storage under ambient conditions. The therapeutic efficacy of ETD including analgesic activity and anti-inflammatory effect was monitored. Results: The prepared ETD organogels showed suitable properties for topical application and the selected formulae (F3, F14 & F39) showed enhanced permeation. The In vivo study showed a significant difference in the therapeutic efficacy of formula F14, containing 10% IPM, 40% lecithin/PG in the ratio of (5:1) and 50% water, compared to a market product. Skin irritation test and histopathological studies proved the safety of this formula. Conclusion: So this organogel formula (F14) is considered to be a potential vehicle for a sustained release transdermal delivery system for ETD.