topiramate and Facial-Pain

NMDA and non-NMDA receptors are involved in spinal transmission of nociceptive information in physiological and pathological conditions. Our objective was to study the influence of NMDA and non-NMDA receptor antagonists on pain control in the trigeminal system using a formalin-induced orofacial pain model. Motor performance was also evaluated. Male Rattus norvegicus were pre-treated with topiramate (T) (n=8), memantine (M) (n=8), divalproex (D) (n=8) or isotonic saline solution (ISS) (n=10) intraperitoneally 30 minutes before the formalin test. Formalin 2.5% was injected into the right upper lip (V2 branch) and induced two phases: phase I (early or neurogenic) (0-3 min) and phase II (late or inflammatory) (12-30 min). For motor behavior performance we used the open-field test and measured latency to movement onset, locomotion and rearing frequencies, and immobility time. Pre-treatment of animals with M and D only attenuated nociceptive formalin behavior for phase II. T increased locomotion and rearing frequencies and reduced immobility time. Treatment with M increased immobility time and with D reduced locomotion frequency. Our results showed that the NMDA antagonist (M) is more potent than the non-NMDA antagonists (D and T) in the control of pain in the inflammatory phase. The non-NMDA topiramate improved motor performance more than did D and M, probably because T has more anxiolytic properties.

Topics: Animals; Exploratory Behavior; Facial Pain; Fructose; Inflammation; Male; Memantine; Motor Activity; Pain Measurement; Placebos; Rats; Receptors, N-Methyl-D-Aspartate; Topiramate; Trigeminal Neuralgia; Valproic Acid

A case of chronic neuropathic pain in the infraorbital region following an untreated displaced zygomatic fracture is presented. The case responded favorably to topiramate and sensory testing revealed signs of nerve damage that remained unchanged over the follow-up period (six months) parallel to an analgesic effect. The clinical pharmacology of topiramate, which is reviewed, includes enhanced neuronal stability and neuroprotection, making it a possible candidate in the treatment of painful orofacial neuropathies.

Topics: Analgesics, Non-Narcotic; Anticonvulsants; Facial Pain; Female; Fructose; Humans; Middle Aged; Orbit; Pain Measurement; Sensory Thresholds; Topiramate; Trigeminal Nerve Diseases; Zygomatic Fractures