Abstract
Background: Despite the availability of several drug classes for treatment of neuropathic pain, no one provides the optimal balance of efficacy, tolerability and safety. Paracetamol (acetaminophen) is widely used for reducing pain with various origin around the world. The aim of this study was to compare the analgesic effect of intraperitoneally and intrathecally administration of paracetamol in chronic constriction Injury (CCI) model of the sciatic nerve in male rats.
Method: In this study, 24 adult male Wistar rats were randomly divided into 2 groups (n=12). The CCI model of sciatic nerve was used for induction of neuropathic pain. Catheterization was performed on the eleventh day after injury through the space between the L5 and L6. On the fourteen days after injury, paracetamol injected intraperitoneally (100mg/kg) and intrathecally (50μg / rat) in two different groups. Thermal and mechanical hyperalgesia and cold allodynia evaluated 15, 60 and 120 minutes after injection. The intact limb was used as control.
Results: Injury of the sciatic nerve induced a significant decrease in pain threshold. Both intraperitoneal (p<0.001) and intrathecal (p<0.001) administration of paracetamol reduced the pain and this effect continued until 120 minutes after injection. However, paracetamol does not increase the pain threshold of injured hindpaw to the uninjured one. The effectiveness of paracetamol was similar in both methods of administration (p>0.05).
Conclusion: The findings of this study indicate that intraperitoneal and intrathecal administration of paracetamol had no significant difference in pain symptoms. Therefore, because of convenience and lower risk, intraperitoneal administration is recommended to relief the pain.