Optimizing dermatological formulations of retinoic acid

Development of tretinoin gels for enhanced transdermal delivery

To develop the new gel formulations that show sustained release for a period of time, the bioadhesive carbopol gels containing tretinoin were prepared. The release characteristics of drug from the carbopol gel were studied according to temperature, receptor medium and drug concentration. For the enhancement of its percutaneous absorption, some kinds of penetration enhancer were used. As the concentration of drug increased, the release of drug from the gel increased, showing concentration dependency. The increase of temperature showed the increased drug release, depending on the activation energy of permeation. Among the enhancers used such as the glycols and the non-ionic surfactants, polyoxyethylene 2-oleyl ether showed the best enhancing effect. The carbopol gels of tretinoin containing an enhancer could be developed for the enhanced transdermal delivery of drug.

Novel concept for a mucosal adhesive ointment

Conventional adhesive ointments cause irritation to the mucous membranes. Therefore, a novel mucosal adhesive ointment based partly on neutralized polymethacrylic acid methyl ester was formulated. The flow curves of the ointment vehicle showed pseudoplastic properties. The rheological behavior as well as the adhesion on the mucosal membrane could be varied by the type and concentration of the polymer used and the base used for neutralization. During clinical studies, the ointment vehicle as well as a tretinoin (vitamin A acid) preparation for the treatment of lichen planus did not cause any local irritation or systemic side effects. Both vehicle and preparation were found to be pleasant for the patients to use. The new system of the mucosal adhesive ointment is not limited to the incorporation of tretinoin as the active agent; combined with other drugs the system could be applied to all types of mucosal membranes.