Objective: The aim of the present investigation was to carry out a comparative evaluation of
skin permeation potential of microemulsion (ME) and niosome based topical gel formulations along
with marketed gel products containing diclofenac sodium (DS).
Methods: For ME formulation, solubility studies were done to select optimum oil, surfactant (S) and
co-surfactant (CoS). Pseudoternary phase diagrams were constructed using water titration method at
different S: CoS ratios to determine ME region. Niosomes were optimized for % drug entrapment using
sequential optimization approach for four different factors, surfactant type, solvent ratio,
S:Cholesterol ratio and drug amount (mg) at 3 levels. Optimized ME and niosomes were incorporated
into carbopol gel base to obtain 1% DS carbopol gel. Both the ME gel and Niosome gel were compared
with marketed diclofenac gels. Prepared ME, Noisome gels and marketed A, B and C gels
(coded) were evaluated for visual appearance, pH, viscosity, spreadability, mechanical stress studies,
% assay and ex vivo
skin permeation and retention studies using rabbit skin.
Result and Discussion: The pH, spreadability, results of mechanical stress studies and drug content
were within the acceptable limits. All gels exhibited pseudoplastic behavior, ME gel showed the highest
flowability. The percent drug permeations from different gels were found to be in the range of
19.35% to 57.86 % through rabbit skin over twelve hrs. Marketed gel B showed the highest permeation
followed by niosomal gel and ME. However, the release of DS from niosomal gel showed more uniform
drug release pattern. Also, the drug retention in the skin after 12 hrs for niosomal gel was significantly
higher (44.35%, p < 0.01) followed by ME gel (32.24%, p < 0.05) compared to marketed gels.
Conclusion: Our results suggest that the DS niosomal gel significantly enhances both skin permeation
and retention and provides more uniform drug permeation through the skin compared to prepared ME
and marketed gels.