Local anesthetic effect and safety of ropivacaine oily solution

Purpose: To investigate the effectiveness and safety of ropivacaine oily solution (ROPOS). Methods: After effecting nerve block in postoperative rats by injection of ROPOS near the sciatic nerve, the expression levels of sodium-potassium-chloride co-transporter 1 (NKCC1) and potassium-chloride co-transporter 2 (KCC 2) in the spinal dorsal horn, were assayed. The safety of ROPOS in beagle dogs was evaluated through subcutaneous injection. Results: The duration of anesthetic effect of ROPOS was 5 times longer than that of ropivacaine hydrochloride injection. The analgesic effect occurred via downregulation of the expression of NKCC1. Dogs administered ROPOS had acute inflammatory reactions at the injection sites within 3 days, but they recovered after 14 days. No other toxic reactions were observed. The Tmax values for dogs subcutaneously injected with ROPOS at doses of 15, 30 and 60 mg/kg were 2.15 ± 3.09, 6.25 ± 9.62 and 14.85 ± 11.82 h; with the Cmax values of 0.78 ± 0.51, 1.35 ± 0.38 and 2.09 ± 0.53 µg/mL, while the AUC(0-48h) values were 15.88 ± 5.41, 31.46 ± 11.45 and 66.10 ± 17.81 h·µg/mL, respectively. The values of Tmax, Cmax and AUC(0-48h) were positively correlated with ROPOS dose. Conclusion: Ropivacaine oily solution has a longer duration of local anesthetic effect than ropivacaine hydrochloride injection and it also possesses a good safety profile. The acute inflammatory reactions are noteworthy and will be further investigated in subsequent studies.