Background: Various analgesics adjuvants, including opioids, have been tested and demonstrated to be clinically beneficial when added to local anesthetics in an attempt to increase the duration of analgesia with the risk of various adverse effects. This study was designed to test the hypothesis that scorpion venom peptide, BmK AGAP as an adjuvant to lidocaine causes dose-dependent increase intensity of sensory block and prolong duration of analgesia.
Method: We performed partial sciatic nerve ligation on 60 rats to induce a rapid onset and long-lasting mechanical allodynia. Equal volume (600µl) of preservative-free lidocaine (0.5%) and BmK AGAP (2 or 1 mg/kg) were prepared with saline (0.9%). The rats were randomly allocated into five groups. Group A (n=12) received saline as the negative control; Group B (n=12) received equal volume of lidocaine and saline; Group C (n=12) received lidocaine and BmK AGAP (1 mg/kg); Group D (n=12) received lidocaine along with BmK AGAP (2 mg/kg) and Group E (n=12) sham. We operated on the rats representing the sham group (n=12) and the sciatic nerve exposed but not ligated. The von Frey filaments were used to assessed mechanical allodynia in rats.
Results: The data showed that rats from the lidocaine group exhibited increased 12.51g of PWT. The rats from the BmK AGAP (1 mg/kg) group exhibited increased 13.67g of PWT, whereas the rats from the BmK AGAP (2mg/kg) group exhibited increased 14.78g of PWT compared with the baseline PWT. There was a prolonged duration of increased paw withdrawal threshold in rats that were supplemented with BmK AGAP compared with rats that received lidocaine injection alone. We realized a significant (P< 0.0001) prolonged duration of increased paw withdrawal threshold in rats that were supplemented with BmK AGAP (2 mg/kg) compared with rats that received BmK AGAP (1 mg/kg).
Conclusion: This study finding suggests scorpion venom peptide, BmK AGAP to be a potent analgesic adjuvant. BmK AGAP as an adjuvant to lidocaine in sciatic nerve block increase the intensity of sensory block and prolongs perioperative analgesia without significant adverse effects.
Keywords: Scorpion venom peptide, BmK AGAP, nerve block, adjuvant, perioperative analgesia