An Experimental Comparison of the Analgesic and Anti-Inflammatory Effects of Safflower Oil, Benzydamine HCl, and Naproxen Sodium

The study aims to establish how feasible a natural therapy option (safflower oil) is in the treatment of postoperative pain. Naproxen sodium has already been experimentally proven to be effective for this purpose. Accordingly, the analgesic and anti-inflammatory effects of safflower oil were compared with those obtained with benzydamine HCl and naproxen sodium. Forty-two, healthy, adult female rats of Wistar albino species were divided at random into six groups of seven rats. The intervention allocation was as follows: Group No. 1—physiological saline 0.9%; Group No. 2—safflower oil 100 mg/kg; Group No. 3—safflower oil 300 mg/kg; Group No. 4—benzydamine HCl 30 mg/kg; Group No. 5—benzydamine HCl 100 mg/kg; and Group No. 6—naproxen sodium 10 mg/kg. Following allocation of treatment, pain was induced experimentally and tested in various ways (hot plate test, tail-pinching test, and writhing test) and the efficacy of each treatment in providing peripheral and central analgesia was evaluated. The second stage consisted of providing different treatments to four groups (groups 7–10) of seven rats each, chosen at random. The allocations were as follows: Group No. 7—physiological saline 0.9%; Group No. 8—safflower oil 300 mg/kg; Group No. 9—benzydamine HCl 100 mg/kg; and Group No. 10—naproxen sodium 10 mg/kg. To create experimental inflammation, 2% formaldehyde was injected into the experimental animal's paw and the resulting edema was measured and recorded for a 10-day period. Edema inhibition was calculated as a percentage. The rats were sacrificed and the paw and stomach dissected for histopathological examination. The data were used for statistical analysis, using the Shapiro–Wilk, Kruskal–Wallis H test, and two-way analysis of variance. In the tail-pinching test, it was determined that a 300 mg/kg dose of safflower oil shows central spinal analgesic efficacy and this effect is close in magnitude to 10 mg/kg of the reference material, naproxen sodium. In the squirming test, it was observed that the 100 and 300 mg/kg doses of safflower oil had a peripheral analgesic effect when compared with the serum physiological (placebo) group. The peripheral efficacy of 300 mg/kg safflower oil was found to approximate that of 10 mg/kg naproxen sodium. In rats treated with benzydamine HCl 100 mg/kg, similar peripheral analgesic efficacy to naproxen sodium 10 mg/kg was noted. In the hot plate test, no difference in the analgesic efficacy between the various agents was found. The change in inhibition of edema between the 1st and 10th days was most marked in rats receiving naproxen sodium 10 mg/kg. A significant difference was determined in the safflower oil 300 mg/kg and benzydamine HCl 100 mg/kg groups (P < .001). Regarding histopathology findings in the rat paw, significant differences were seen in venous congestion between placebo and safflower oil 300 mg/kg and in inflammation between the control and benzydamine HCl 100 mg/kg groups. Regarding the histopathology findings in the rat stomach, significant differences were observed in venous congestion between placebo and safflower oil 300 mg/kg; in damage to the epithelium between placebo and safflower oil 300 mg/kg and between naproxen sodium 10 mg/kg and safflower oil; and in cell infiltration and development of edema between placebo and safflower oil 300 mg/kg. It is predicted that further research into safflower oil and benzydamine HCl will create opportunities to develop analgesic–anti-inflammatory therapeutics of a novel kind for the treatment of postoperative pain and inflammation.