Antinociceptive effects of ceftriaxone in formalin-induced nociception.

Ceftriaxone (CFX) is a β-lactam antibiotic with analgesic properties. However, its role in the formalin-induced nociception remains unknown. The purpose of this study was to investigate the antinociceptive effect of CFX in the 1% formalin test in rats. Formalin induced a typical nociceptive response (flinching behavior) of two phases. Local peripheral pretreatment (20 min) with CFX (400-800 μg/paw) slightly attenuated the flinching behavior in phase 2, but not phase 1. Acute intraperitoneal pretreatment (20 min) also reduced phase 2 of the formalin test. In both cases, CFX induced a dose-dependent antinociception. We also tested the effect of CFX 1 day after its administration and in two schedules of repeated administration. One-day pretreatment with CFX (50-400 mg/kg, ip) induced a dose-dependent antinociceptive effect in formalin-treated rats. Repeated administration (daily during 3 or 7 days) with CFX (50-400 mg/kg, ip) diminished formalin-induced nociception. Results suggest that local or systemic as well as single or repeated administration of CFX reduces formalin-induced nociception.