Pharmacokinetics of eugenol and its effects on thermal hypersensitivity in rats

• Published in: European journal of pharmacology Vol. 562; no. 1; pp. 60 - 67
• Main Authors: Guénette, Sarah Annie, Ross, Andréanne, Marier, Jean-Francois, Beaudry, Francis, Vachon, Pascal
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 07.05.2007; Elsevier
• Subjects: Algorithms; Animals; Area Under Curve; Biological and medical sciences; Clove Oil - chemistry; Cranial nerves. Spinal roots. Peripheral nerves. Autonomic nervous system. Gustation. Olfaction; Eugenol; Eugenol - administration & dosage; Eugenol - blood; Eugenol - pharmacokinetics; Hyperalgesia - physiopathology; Hyperalgesia - prevention & control; Hyperalgesia and allodynia; Male; Medical sciences; Metabolic Clearance Rate; Nervous system (semeiology, syndromes); Neuralgia - physiopathology; Neuralgia - prevention & control; Neurology; Neuropathic pain; Pharmacology. Drug treatments; Rats; Rats, Sprague-Dawley; Sprague–Dawley rats; Time Factors; Eugenol; Sprague–Dawley rats; Hyperalgesia and allodynia; Neuropathic pain; Allodynia; Nervous system diseases; Rat; Hypersensitivity; Rodentia; Peripheral neuropathy; Hyperalgesia; Vertebrata; Sprague-Dawley rats; Mammalia; Pain; Animal; Peripheral nerve disease; Neuralgia; Neurological disorder; Pharmacokinetics
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/j.ejphar.2007.01.044

Neuropathic pain is a type of chronic pain following central or peripheral nervous system lesions that cause allodynia (pain initiated by a non-painful stimulus) and hyperalgesia (increased pain sensation following a painful stimulus). The first objective of the study was to evaluate the pharmacokinetics of eugenol, the principle chemical constituent of clove oil, following a gavage administration (40 mg/kg) in male Sprague–Dawley rats. The second objective was to evaluate the effect of repeated oral administrations of eugenol on hyperalgesia and allodynia using an experimental model of neuropathic pain in rats. Thermal and mechanical sensitivity (Hargreave's test and von Frey filaments) were determined in sciatic nerve cuff-implanted rats. Sensitivities were assessed following repeated oral administrations of 40 mg/kg of eugenol or saline for 5 days ( n = 6 per group). Pharmacokinetic parameters were calculated using noncompartmental methods. Serial blood samples were collected over 24 h. Concentrations of eugenol in blood and plasma peaked rapidly following oral administration. Mean T 1/2 values of eugenol in plasma and blood were long (14.0 and 18.3 h, respectively), suggesting a potential accumulation of the drug following repeated administrations. Reaction time to thermal stimuli appeared to increase constantly following repeated administrations of eugenol. On the last day of treatment, eugenol treatments resulted in a statistically significant prolongation of the reaction time to thermal stimuli in rats compared to the saline group (Mean ± S.E.M.: 11.4 ± 1.23 vs. 6.1 ± 0.53 s, P < 0.01). These results support the hypothesis that eugenol may alleviate neuropathic pain and that the cumulative effect of the drug may be in part responsible for this effect following repeated daily administrations.