Eavaluating antinociceptic effect of nano-emulsion gel conataining rosemary and peppermint essential oils in a rat model of osteoarthritis

Background and Aim: Despite identification of the antinociceptive effects of rosemary and peppermint essential oils, use of these essential oils has been limited due to its low solubility in water and low bioavailability. Use of nanoparticles is one of the ways to overcome these limitations. The aim of this study was to evaluate the antinociceptive effect of nano-emulsions containing rosemary and peppermint essential oils in an animal model of osteoarthritis (OA). Materials and Methods: In this experimental study nano-emulsions containing rosemary and peppermint essential oils were prepared by spontaneous emulsification. In order to investigate the analgesic effect, 30 male rats were randomly assigned to 5 groups: sham (receiving saline injection into the knee), osteoarthritis(receiving intra-articular injection of 2 mg monosodiumiodoacetate), OA (receiving gels containing nano-emulsion, or rosemary and peppermint essential oil or diclofenac sodium). Treatments were administered topically at a dose of 1 ml daily. Mechanical and thermal allodynia and thermal hyperalgesia tests were performed on the 1st, 4th , 7th and 14th days after injection. Data were analyzed by repeated measures ANOVA. Results: OA group showed a significant increased behavioral response to the mechanical and thermal stimuli on all days of the experiment compared to the control group (P