The "PINK SPOT" in schizophrenia.
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Chemical Phenomena↗
Biomedical subjects
N Wad
Publications and source records attributed to N Wad.
Pharmacokinetics of R-enantiomeric normephenytoin during chronic administration in epileptic patients.
Stereoselective metabolism has been demonstrated for mephenytoin (MHT), R-MHT being demethylated to the pharmacologically active metabolite 5-phenyl-5-ethylhydantoin (PEH; nirvanol), and S-MHT undergoing aromatic hydroxylation to 4-OH-MHT, with formation of an intermediate arene oxide metabolite. PEH is responsible for the therapeutic effect, whereas 4-OH-MHT is rapidly eliminated by the kidneys. The arene oxide metabolite may have implications in MHT toxicity. The metabolism of PEH is also stereospecific. In the present study, the R-enantiomer of PEH (R-PEH; R-normephenytoin) was administered chronically during 8 weeks to four epileptic patients, as a single dose every 3 days. The half-lives of R-PEH ranged from 77.7 to 175.8 h, and correlated closely with the creatinine clearance. Mean urinary recovery of R-PEH was 86.6% of the dose at steady state, with 4-OH-PEH accounting for only 5%. This indicates that, unlike Nirvanol (a racemic mixture of R- and S-PEH), R-PEH is only minimally metabolized, even after several weeks of treatment and despite potential enzymatic autoinduction and heteroinduction by other antiepileptic drugs. Complete blood counts and liver function tests revealed no alteration, and no other adverse effects were noted. If arene oxide intermediate metabolites are indeed involved in the toxicity of MHT and nirvanol, R-PEH may represent a safer alternative.
Adult↗
Combined administration of carbamazepine and phenobarbital: effect on anticonvulsant activity and neurotoxicity.
Despite the trend towards single drug therapy of epilepsy, patients resistant to monotherapy are commonly treated with more than one antiepileptic drug. As part of an investigation on the experimental background for antiepileptic drug combinations, the effect of the pharmacodynamic interactions between carbamazepine and phenobarbital on the toxicity/efficacy ratio was studied in mice. All results were expressed in terms of drug concentrations in the brain to exclude possible pharmacokinetic interactions from the analysis. A purely additive interaction was found for the anticonvulsant as well as for the neurotoxic effect of the drugs. The combination of carbamazepine and phenobarbital has therefore no advantage over each drug alone in this model. Based on these and previous results, there is no experimental evidence in favor of any combination between the four main drugs against partial seizures, i.e., carbamazepine, phenytoin, phenobarbital, and primidone.
Animals↗
Serum protein binding of desmethyl-methsuximide.
Serum protein binding of desmethyl-methsuximide (DM-MSM) in serum from 23 patients on polytherapy were determined using ultrafiltration and high-performance liquid chromatography. Desmethyl-methsuximide, The active metabolite of methsuximide (MSM), was found to have a moderate protein binding ranging between 45% and 60%.
Anticonvulsants↗