Shock/sepsis/trauma/critical careNasal inhalation of butorphanol in combination with ketamine quickly elevates the mechanical pain threshold in the model of chronic constriction injury to the sciatic nerve of rat

BackgroundThe aim of the present study is to explore the impact of butorphanol in combination with ketamine via nasal inhalation (NI) on neuropathic pain induced by chronic constriction injury (CCI) to the sciatic nerve in a rat model.MethodsCCI rats (n = 12) were equally randomized to four groups based on the treatments received as follows: 100 μL of 0.9% normal saline via NI (NS/NI group); 100 μg of butorphanol plus 1 mg of ketamine via NI (B + K/NI group); 100 μg of butorphanol alone via NI (B/NI group); and 100 μg of butorphanol plus 1 mg of ketamine via subcutaneous injection (B + K/SC group). Mechanical pain threshold was measured at 10 min, 30 min, 2 h, 4 h, and 6 h after drug administration.ResultsThe mechanical pain threshold in the B + K/NI group was improved significantly 4 h after drug administration as compared with that in the B/NI or B + K/SC group (P < 0.05). The onset and intensity of drug action in the B + K/NI group were better than those of the other two groups, but the duration of drug action was not prolonged.ConclusionsNI of butorphanol in combination with ketamine quickly elevates the mechanical pain threshold in a rat neuropathic pain model induced by CCI to the sciatic nerve.