Release Kinetics of Tretinoin from Dermatological Formulations

Tretinoin, or retinoic acid, can be used in the treatment of a variety of skin diseases, depending on its concentration. Formulations containing tretinoin 1 % have been used in the therapy of malignant cutaneous diseases, namely, Kaposi 's syndrome. In lower concentrations, it has been used in antiacne formulations and in the treatment of anti-aging effects on photodamaged skin. The aim of the present study was to determine the variation profile of in vitro release of tretinoin, in order to establish the drug's partition coefficient between its carrier and the stratum corneum. The samples studied were formulations of tretinoin 0, 05% in carbopol 940 (a synthetic polymer), sodium carboxymethylcellulose (a semisynthetic polymer), and carob gum (a natural polymer) gels. The release profiles obtained from these formulations were compared to release profiles of retinoid creams. The formulations studied exhibited both good chemical and physical stabilities when submitted to rheological determinations, pH measurements, and drug dosage, throughout a 6-month period. The obtained results show that identical polymer viscosities result in identical release profiles; however, the release kinetics of tretinoin varies strongly in the way in which the drug is incorporated in the formulation (whether it is a solution or a suspension).