Effects of vehicle on diclofenac sodium permeation from new topical formulations: in vitro and in vivo studies

In this study the effect of vehicle on in vitro diffusion of diclofenac sodium (DS) from new different formulations such as Carbopol gel (A), Sodium lauryl sulphate cream (B) and Carbopol cream (C) was evaluated with Franz diffusion cells using hydrophilic and hydrophobic synthetic membranes. The commercial formulation Voltaren® Emulgel was used as reference. Furthermore, the in vivo efficacy of topical formulations was studied in the carrageenan-induced edema and hyperalgesia, whereas the antinociceptive effect was evaluated on thermal pain threshold in rat paw. The flux of DS across hydrophilic membranes showed this rank order: Control C > A B. On the other hand, the diffusion rate of DS across hydrophobic membranes resulted in the following order: Control > B > A C; this suggested a lower interaction between the vehicles and these membranes. The in vivo results indicated that the prepared formulations failed in the inflammatory tests to reduce the development of edema. Nevertheless, treatment with B formulation inhibited the development of acute hyperalgesia induced by carrageenan, and elicited a significant increase in paw withdrawal latencies whereas other formulations were ineffective. The results obtained in this study suggest that Sodium lauryl sulphate cream might be useful in local pain conditions and may be an effective alternative to the presently used systemic routes.