Relationship Between Paracetamol Plasma Levels and its Analgesic Effect in the Rat

Abstract
The relationship between plasma levels of paracetamol and its analgesic effect was studied in the rat using a model of pain-induced functional impairment (PIFI). Female Wistar rats received an intraarticular injection of 30% uric acid in the knee of the right hind limb, inducing its dysfunction. Animals then received oral paracetamol at doses of 178, 316 or 562 mg kg−1and the recovery of functionality over time was considered as an expression of analgesia. Paracetamol plasma levels were determined by HPLC. Results showed that there is a direct relationship between paracetamol plasma levels and its analgesic effect that follows a sigmoidal model according to the Hill equation. The PIFI model appears to be a useful tool to establish pharmacokinetic/pharmacodynamic relationships for non-narcotic analgesics.
Funding Information
  • Cosnet-SEP (PEP 18.89)

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