Quantitation of the novel anticonvulsant remacemide in rat and dog plasma and urine: application of the plasma methodology to measure the plasma protein binding of remacemide

Determination of antiepileptic drugs in biological material

Current analytical methodologies applied to the determination of antiepileptic drugs in biological material are reviewed. The role of chromatographic techniques is emphasized. Special attention is focused on new chemical entities as well as current trends such as high-speed liquid chromatographic techniques, hyphenated techniques and electrochromatography techniques. A review with 542 references.

Simultaneous determination of remacemide hydrochloride and desglycinylremacemide (AR-R12495XX) in brain tissue by high-performance liquid chromatography

Remacemide hydrochloride, a novel anticonvulsant agent, and its major active metabolite, desglycinylremacemide, were measured simultaneously in brain tissue by high-performance liquid chromatography with UV detection. Intra- and inter-assay variations for remacemide (1, 5, 10 microg/ml) were 5.1, 10.5 and 3.1% and 3.1, 4.0 and 1.3%, respectively. Intra- and inter-assay variations for desglycinylremacemide (1, 5, 10 microg/ml) were 4.2, 3.8 and 8.4% and 7.9, 8.8 and 3.1%, respectively. Limits of detection and quantification for both analytes were 4 and 31 ng/ml, respectively, with recovery consistently > or =85%. This reliable assay has applications in the pre-clinical neuropharmacokinetic and neuropharmacodynamic investigation of remacemide hydrochloride.

Remacemide: current status and clinical applications

Remacemide (RMC) is a non-competitive, low-affinity N-methyl-D-aspartate (NMDA) receptor antagonist that does not cause the behavioural and neuropathological side effects seen with other NMDA receptor antagonists. RMC and its active metabolite, AR-R 12495 AR, which has moderate affinity for the NMDA receptor, also interact with voltage-dependent neuronal sodium channels. Both agents show efficacy in a variety of animal models of epilepsy, parkinsonism and cerebral ischaemia. There is no evidence for teratogenicity or genotoxicity. RMC delays the absorption of L-dopa and elevates the concentrations of drugs metabolised by the hepatic cytochrome P450 3A4 isoform. RMC and AR-R 12495 AR have moderate protein binding and linear pharmacokinetics. Controlled studies show evidence of efficacy in treating epilepsy and Parkinson's disease. Post-surgical outcomes in RMC-treated patients at risk for intra-operative cerebral ischaemia are also encouraging. Adverse effects are related to the gastrointestinal and central nervous systems. RMC is a promising drug with numerous potential applications for both acute or chronic conditions associated with glutamate-mediated neurotoxicity.

Dizocilpine-like discriminative stimulus effects of low-affinity uncompetitive NMDA antagonists

The dizocilpine-like discriminative stimulus effects of a variety of channel blocking (uncompetitive) N-methyl-D-aspartate (NMDA) receptor antagonists were examined in rats trained to discriminate dizocilpine (0.17 mg/kg, i.p) from saline in a two-lever operant procedure. The dissociative anesthetic-type NMDA antagonists dizocilpine (ED50 0.05 mg/kg), phencyclidine (ED50 3.4 mg/kg) and ketamine (ED50 14 mg/kg) showed complete substitution without producing significant decreases in response rates, whereas dexoxadrol (ED50 4.3 mg/kg) also produced complete substitution with a concomitant decrease (35%) in response rate. Similarly, the low-affinity antagonist memantine resulted in complete substitution (ED50 9.7 mg/kg) at doses that significantly reduced (68%) the response rate. All other low-affinity antagonists resulted in either partial or no substitution for the discriminative stimulus effects of dizocilpine at doses that significantly decreased average response rates. These include (ED50 values in parentheses) remacemide (29 mg/kg), the remacemide metabolite 1,2-diphenyl-2-propylamine (ARL 12495) (14 mg/kg), phencylcyclopentylamine (25 mg/kg), dextromethorphan (46 mg/kg), (+/-)-5-aminocarbonyl-10,11-dihydro -5H-dibenzo-[a,d]cyclohepten-5,10-imine (ADCI; no substitution) and levoxadrol (no substitution). We conclude that low-affinity uncompetitive NMDA antagonists have discriminative stimulus properties distinct from dissociative anesthetic-type uncompetitive NMDA antagonists. The lowest-affinity antagonists show virtually no substitution for dizocilpine, whereas the relatively more potent low-affinity antagonists (such as memantine) exhibit greater substitution, but complete substitution is obtained only at rate-reducing doses.