LECITHINISED MICROEMULSIONS FOR TOPICAL DELIVERY OFTRETINOIN

Tretinoin is indicated for the management of acne, photoaged skin, psoriasis and other skin disorders and also for severe conditions like acute promyelocytic anaemia and squamous cell carcinoma of the skin. The potential of tretinoin in these conditions is limited due to want of a proper delivery vehicle. In order to develop alternate formulations for the topical administration of tretinoin, lecithinsed microemulsions were prepared and evaluated as delivery vehicles. These systems were prepared using phosphate buffer pH 5.5, isopropyl myristate, tween 80 and ethanol. The microemulsions were characterized using TEM. The ability of the system to deliver tretinoin into and through the skin was evaluated in vitro using the skin of laca mice. The in vitro permeation data showed that the novel microemulsions increased tretinoin penetration through the skin; higher flux (33.92 µg / cm2 / hr) was obtained with microemulsion formulation and microemulsified gel (31.54 µg / cm2 / hr) in comparison to the plain drug solution (22.33 µg / cm2 / hr), plain drug in gel (28.67 µg / cm2 / hr) and the marketed preparation (24.28 µg / cm2 / hr). These results were supported by skin retention study and it was noted that the maximum amount retained was with microemulsified gel (96.28 µg / cm2) and non-gel (82.13 µg / cm2) respectively. The other systems; drug in solution, drug in gel (conventional) and marketed preparation were able to retain the drug at the level of 32.4 µg/ cm2, 21.54 µg / cm2 and 29.32 µg / cm2 respectively. These results suggest that the studied microemulsions may be appropriate vehicles for topical delivery of tretinoin.