Determination of the Maximum Nonlethal Dose of Lidocaine and Epinephrine Based on Subcutaneous Injection in Rabbits

Abstract

Background: The objective of the present study was to determine the maximum nonlethal dose of epinephrine, lidocaine, and both substances diluted in saline subcutaneously injected in rabbits. Methods: The animals were divided into three groups. The first group received a maximum dose of subcutaneous epinephrine diluted in 30mL of saline with decreasing doses of epinephrine: 10.01mg/kg, 7.25mg/kg, 5.32mg/kg, 2.51mg/kg, 1.85mg/kg, 2.8mg/kg, and 1.21mg/kg. The second group received 30mL of saline with decreasing doses of lidocaine 250, 200, 150, 125, 100, 75, and 50mg/kg, respectively. The animals were observed from 48 hours to 7 days after receiving the injection. The third group also received 30mL of saline containing a fixed dose of 0.03mg of epinephrine and the same decreasing doses of lidocaine as the second group. After receiving the injection, the animals were observed for 48 hours for adverse reactions, death, and absence of vital signs. Results: In the first group, the dose of 1.21mg/kg of epinephrine has proved to be nonlethal. In the second group, a dose of 50mg/kg of lidocaine subcutaneously injected to rabbits caused neither visible reactions nor death. Finally, in the third group, lidocaine plus epinephrine at a dose of 75mg/kg plus 0.03mg in the saline did not cause visible reactions or death. Conclusion: Lidocaine injected into the subcutaneous tissue of rabbits at a dose of 50mg/kg did not cause visible reactions or death.