Evaluation of bases for topical preparations by microdialysis

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Microdialysis has been used to determine effects of bases for topicaland transdermal preparations of salicylic acid , indomethacin and effects of absorption enhancer for transdermal delivery of tranilast. The ointment bases examined were solbase, poloid, white petrolatum, hydrophilic poloid absorptive ointment, hydrophilic ointment. Also, gel and cream preparation of indomethacin on market were used. Results obtained in this study were as folows :(1) Recovery % of salicylic acid in the dialysate was 4.8%. (2) In case of solbase, transfer of salicylic acid to intact skin was remarkably less than the skin without stratum corneum. maximum concentration of salicylic acid in intact skin tissue was 68mu M and the value increased by5Ot imes by removal of stratum comeum. (3)In case of poloid, transfer of salicylic acid was fairly good and maximaum concentration in intact skin tissue was 622mu M.White petrolaum showed similar results. (4) Hydrophilic poloid and absorptive ointment showed similar results to poloid. (5)Theratio of area under the curve of concentration in skin tissue vs. time to area under the curve of concentration in plasma was greater in hydrophobic base and absorptive ointment. These results suggest that hydrophobic base and absorptive ointment are useful as a base for drugs of topical action. (6)Recovery % of indomethacin in the daillysate was 5.2%. Transfer of indomethacin to skin tissue from hydrophilic ointment and absorptive ointment was good and maximum concentration in skin tissue was 30-65mu M.Similar results was obtained in commercial preparations of indomethacin. (7)A mixture of oleic acid 20% and propyleneglycol 10% was most effectve as a absorption enhancer for tranilast. (8)Finally, it is recognized that microdialysis is a useful technique for evaluation of function of topical transdermal delivery preparations.