ricinoleic-acid and Edema

Our previous study showed that the use of ricinoleic acid as an oil phase resulted in the formation of a stable pluronic lecithin organogel (PLO gel) with better thixotropic properties and higher permeation of ketoprofen than the isopropyl palmitate PLO gel. This study aims to evaluate and compare the in vitro and in vivo anti-inflammatory effects of the ricinoleic acid PLO gel system with isopropyl palmitate PLO gel. Ketoprofen was used as a model drug. In vitro anti-inflammatory activity and cell viability tests were performed in human rheumatoid arthritis synovial fibroblast cell line using a blank ricinoleic acid PLO gel and compared to that of the isopropyl palmitate PLO gel. In vivo anti-inflammatory activity of ricinoleic acid PLO gel containing 10% ketoprofen was evaluated and compared with the isopropyl palmitate PLO gel in a carrageenan-induced rat paw edema model. The results from the in vitro study showed that the blank ricinoleic acid PLO gel possessed significantly higher anti-inflammatory activity than isopropyl palmitate PLO gel at 1 mM concentration (p<0.05), while both the gel formulations had no significant cytotoxic activity. Further in vivo testing of the formulation showed that the ricinoleic acid PLO gel formulation was significantly more effective in reducing pain and edema when compared to the isopropyl palmitate PLO gel. In addition, the ricinoleic acid PLO gel formulation markedly inhibited the synthesis of prostaglandin E2. In conclusion, the efficacy of PLO gels used in pain management may be enhanced by using ricinoleic acid instead of isopropyl palmitate as an oil phase.

Topics: Administration, Cutaneous; Animals; Anti-Inflammatory Agents; Carrageenan; Cell Survival; Cells, Cultured; Edema; Fibroblasts; Gels; Humans; Male; Pain; Palmitates; Poloxamer; Rats, Sprague-Dawley; Ricinoleic Acids

Observational studies indicate that topical application of ricinoleic acid (RA), the main component of castor oil, exerts remarkable analgesic and anti-inflammatory effects. Pharmacological characterization has shown similarities between the effects of RA and those of capsaicin, suggesting a potential interaction of this drug on sensory neuropeptide-mediated neurogenic inflammation. The aim of this study was to assess RA anti-inflammatory activities in comparison with capsaicin in several models of acute and subchronic inflammation. The acute inflammation was induced by intradermal injection of carrageenan in the mouse or by histamine in the guinea-pig eyelid. In either experiment, the extent of the oedema thickness was measured. Subchronic oedema was induced by complete Freund's adjuvant injection in the ventral right paw of mice. Tissue substance P (SP) was measured in the carrageenan experiments by radioimmunoassay (RIA). It was found that the acute topical application of RA (0.9 mg/mouse) or capsaicin (0.09 mg/mouse) significantly increased the mouse paw oedema induced by carrageenan, while an 8-day repeated topical treatment with the same doses of both compounds resulted in a marked inhibition of carrageenan-induced paw oedema matched by a reduction in SP tissue levels. Similar effects were found against histamine-induced eyelid oedema in guinea-pigs after acute or repeated application of RA or capsaicin. RA and capsaicin given for 1-3 weeks reduced the established oedema induced by Freund's adjuvant, a subchronic model of inflammation, particularly if given by the intradermal route. Either in mouse paw or in guinea-pig eyelid, capsaicin but not RA by itself produced a slight hyperemia and activation of a behavioural response (e.g. scratching of the eyelids). On the basis of the present results, RA may be seen as a new capsaicin-like, non-pungent anti-inflammatory agent suitable for peripheral application.

Topics: Acute Disease; Administration, Topical; Animals; Anti-Inflammatory Agents; Anti-Inflammatory Agents, Non-Steroidal; Capsaicin; Carrageenan; Chronic Disease; Disease Models, Animal; Edema; Eyelid Diseases; Eyelids; Freund's Adjuvant; Guinea Pigs; Histamine; Injections, Intradermal; Male; Ricinoleic Acids