Introduction: Etofenamate (2-(2-hydroxyethoxy) ethyl 2-[[3-(trifluoromethyl)phenyl]amino]
benzoate) (ETO) is a yellowish viscous liquid which is a nonsteroidal anti-inflammatory drug (NSAID)
that has been applied topically for joint and muscular pain and soft tissue disorders. Solid lipid nanoparticles
(SLNs) are colloidal drug delivery systems prepared by non-irritant and nontoxic lipids that attract
great interest because of their unique features. Semisolid SLNs are novel approach for dermal application
Aims: The aim of this study was to show the development, validation, and application of a simple, selective
and reliable RP-LC method that was extensively validated for its specificity and stability-indicating
properties from its forced hydrolytic, oxidative, photolytic and thermal degradation products.
Materials and Methods: In addition, the proposed method presented to application of ETO from rat skin
extract in according to the United States Pharmacopeia and International Council on Harmonization
Guidelines. For this reason, XSelect HSS T3 XP (150 x 4.6 mm ID x 2.5µm) (Waters Corp. Milford, MA,
USA) analytical column was chosen for the best resolution. Mobile phase consisted of 0.1 % H3PO4 in
bidistilled water (pH adjusted to 7.0 with 5M NaOH) and acetonitrile in the ratio of (40:60, v/v) with the
flow rate of 1 mL.min-1. The volume of the sample solutions was injected at 10µL and the detector was
set up at 285 nm. The analysis was carried out at a temperature of 45oC.
Coclusion: The developed stability indicating method presented low limit of detection, low limit of quantitation
and good resolution between any of interferences from both commercial formulation and developed
SLN formulation from rat skin, with symmetric, pure and perfect peak homogeneity. High percentage
of recovery results shows that the proposed method is free from the interferences of the commonly
used excipients and additives in the formulations of the commercial product or semisolid SLN formulations
and also biological derivatives.