Single-Dose Toxicity Study of Intramuscular Neuralgia-Pharmacopuncture Injection in Rats

Neuralgia-pharmacopuncture (NP) was recently developed as a water-soluble type of pharmacopuncture inspired by CS (care special pain)-pharmacopuncture. I aimed to evaluate the toxic response and approximate lethal dose of when NP when administered intramuscularly to Sprague Dawley rats.

The experimental group was divided into the NP test substance group and the saline control group and administered at a dose of 1.0 mL/animal to the posterior thigh muscles on both sides using a 1 mL syringe; each group consisted of five males and five females. Each rat was monitored for clinical signs and changes in body weight for 14 days after a single intramuscular injection. After completing observation, necropsy findings and localized tolerance at the injection site were assessed via gross necropsy and histopathological examination.

No deaths occurred in the NP or control group, regardless of sex. During the observation period, no changes (such as general symptoms, weight change, or visual observation results at the time of autopsy) were judged to be due to the test substance. Histopathological examination showed no changes at the administration site judged to be caused by the test substance in either the male or female test substance administration groups. In addition, mononuclear cell infiltration of the outer membrane of the femoris muscle at the administration site was observed at the same frequency and extent in the control and NP groups, and was judged to be caused by physical stimulation by the injection needle; therefore, it had no toxicological significance.

Based on the above results, the approximate lethal dose for a single intramuscular administration of the test substance NP in Sprague-Dawley rats was judged to be > 1.0 mL/animal, and there were no findings that were judged to be due to the test substance at the administration site.