Biological profile of the metabolites and potential metabolites of the anticonvulsant remacemide

Antiparkinsonian effects of remacemide hydrochloride, a glutamate antagonist, in rodent and primate models of Parkinson's disease

Loss of dopaminergic innervation of the striatum results in overactivity of the glutamatergic pathways from the subthalamic nucleus to the internal segment of the globus pallidus and the substantia nigra pars reticulata, the output nuclei of the basal ganglia. Previous work has shown that local blockade of glutamate receptors in the internal segment of the globus pallidus or substantia nigra pars reticulata leads to marked suppression of parkinsonian signs. We have now examined whether systemic administration of a glutamate receptor antagonist has antiparkinsonian effects in rodent and primate models of Parkinson's disease. Remacemide hydrochloride is an anticonvulsant, neuroprotective compound with antagonist activity at the N-methyl-D-aspartate receptor ion channel. In normal rats and monoamine-depleted rats, remacemide hydrochloride did not cause locomotor hyperactivity, unlike MK-801. When monoamine-depleted rats were treated with a subthreshold dose of levodopa methylester, remacemide hydrochloride (5-40 mg/kg, orally) caused a dose-dependent increase in locomotor activity. Moreover, remacemide hydrochloride (10 mg/kg, orally) potentiated the effects of each suprathreshold dose of levodopa methylester tested (100-200 mg/kg, intraperitoneally). Parkinsonian rhesus monkeys were tested with oral doses of vehicle plus vehicle, vehicle plus levodopa-carbidopa, and remacemide hydrochloride (5 mg/kg) plus levodopa-carbidopa. Blinded clinical scoring of videotapes revealed that treatment with remacemide hydrochloride plus levodopa-carbidopa was substantially better than levodopa-carbidopa plus vehicle or vehicle plus vehicle. The effects of remacemide hydrochloride lasted at least 5 hours. We conclude that certain N-methyl-D-aspartate receptor antagonists have antiparkinsonian actions and low potential for side effects. Clinical trials of remacemide hydrochloride in patients with Parkinson's disease may be warranted.

Kainic acid and 4-aminopyridine seizure models in mice: evaluation of efficacy of anti-epileptic agents and calcium antagonists

Seizures may be induced in mice in response to stimulation of subtypes of glutamate receptors by kainic acid or inhibition of certain voltage-dependent potassium channels by 4-aminopyridine (4-AP). The anti-seizure efficacy of intraperitoneally administered anticonvulsants and Ca++ antagonists to CF-1 mice was tested using these models. The order of potency for prevention of kainate convulsions and the subsequent lethality was: dihydropyridine Ca++ antagonists (nicardipine, nisoldipine > nitrendipine > nifedipine > nimodipine) followed by verapamil > prenylamine > diltiazem > flunarizine > remacemide HCl > ethosuximide > valproate. In the 4-AP model the order of potency to prevent hind limb tonic extension was: MK801(+/-) > lamotrigine > phenytoin, phenobarbital > carbamazepine > FPL 12495AA (the desglycine metabolite of remacemide HCl), remacemide HCl > flunarizine > prenylamine >>> valproate. Therefore, compounds that limit activation of kainate receptors and voltage-operated linked calcium channels are active in the kainate model. Agents effective against maximal electroshock appear to be effective in the 4-AP model.

High-performance liquid chromatographic method for the simultaneous measurement of remacemide (a novel anticonvulsant and cerebroprotectant) and an active metabolite in human plasma

A high-performance liquid chromatographic (HPLC) method was developed and validated for the determination of both remacemide (a novel anticonvulsant and cerebroprotectant) and an active, major metabolite in human plasma. After the addition of an internal standard, the analytes were extracted from the plasma by ion-exchange solid-phase extraction and measured by an isocratic HPLC system with ultraviolet detection at 210 nm. The recovery of the analytes was > 90%. The standard curves were linear over the range of quantitation of approximately 10-500 ng/ml for remacemide itself and 15-250 ng/ml for the metabolite. Both intra-day and inter-day accuracy and precision data were excellent. Remacemide and its metabolite were shown to be stable in human plasma for at least a year when stored at -20 degrees C.