Comparative pharmacokinetics and bioavailability study of percutaneous absorption of diclofenac from two topical formulations containing drug as a solution gel or as an emulsion gel.

In a 3-way cross-over study on 12 healthy adult volunteers, the percutaneous absorption of diclofenac (CAS 15307-79-6) was studied for two topical formulations containing 1% diclofenac. The relative bioavailability from the test formulation (a solution gel) in terms of Cmax and AUC, calculated from the amount of drug reaching the systemic circulation, was found to be twice the amount after application of reference product (an emulsion gel). The maximum concentration of the drug, from both topical formulations reaching the blood after cutaneous absorption was less than 10% of that obtained after the parenteral administration, which indirectly is indicative that adverse effects normally related to high drug blood concentrations, such as reached after oral administration, are unlikely to be experienced.