Microemulsion Gels of Tapentadol Hydrochloride: Statistical Analysis of Pharmacokinetics and Skin Irritation Studies

Background: The present study aimed to overcome the drawbacks of tapentadol through the oral route and to assess the significance of microemulsion gels for transdermal delivery via pharmacokinetic approach. Methods: Microemulsions were prepared via a ternary phase diagram. The optimized microemulsion was converted into gels, and the microemulsion was evaluated for particle size, zeta potential and cumulative in vitro drug release, whereas the gel was characterized for viscosity, spreadability, in vitro, ex vivo, in vivo and skin irritation studies. The prepared ME-gel PKs were tested against MEs, oral solution and plain gel. Results: The PK study revealed that the half-life of the ME gel was 2.2-fold greater than that of the oral solution and 1.65-fold greater than that of the plain gel. The MRT of the ME gel was 6-fold greater than that of the oral solution and 3.3-fold greater than that of the plain gel. The overall mean value of the AUC (0-∞) was 3.16 times greater than that of the oral route. The skin irritation studies found that absence of irritation and damage after application of ME-gel. Conclusion: The PK study revealed that ME-gel was effective in pain management. The level A IVIVC between the in vitro fraction of drug released and the fraction of drug absorbed in vivo was 0.9731.