[Stability and detection of metabolites of barbiturates: 2-oxo tetrahydro-3-furoic acids].
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Several 1-(o-aryl)barbituric and -2-thiobarbituric acid derivatives were proven to be chiral in their conformational ground states due to the hindered rotation about the C(aryl)-N(1) bond, by observation of diastereotopic groups (H or CH3) at 5-position of the heteroring by 1H and 13C NMR. Some of the enantiomers were semipreparatively enriched by liquid chromatography on triacetylcellulose or on cellulose tris-(3,5-dimethyl)-phenylcarbamate (chiralcel OD-H). Circular dichroism spectra of the enriched enantiomers have been examined with reference to their stereostructures.
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1 The effect of various concentrations of thiopentone, pentobarbitone, methohexitone, hydroxydione, alphaxalone/alphadolone, ketamine, alpha-chloralose, and urethane on the transport of radiolabelled gamma-aminobutyric acid (GABA) and D-aspartate was investigated. 2 Uptake of the amino acids was weakly inhibited, if at all, by the anaesthetics and it is unlikely that such effects contribute significantly to their physiological function. 3 The spontaneous efflux of GABA and D-aspartate was not detectably altered by any of the drugs tested. 4 Thiopentone, pentobarbitone, methohexitone and hydroxydione inhibited K+-stimulated GABA and D-aspartate release. The other anaesthetics had no effect on K+-stimulated amino acid release. 5 The rank order of potency of the inhibitors of K+-stimulated amino acid release did not correlate with their anaesthetic potency. Furthermore not all inhibitors appeared to be very effective at anaesthetic concentrations. 6 It is concluded that although it is possible that inhibition of excitatory transmitter release may be involved in the anaesthetic action of some anaesthetics, for many of the substances tested in this study such as mechanism does not appear to be implicated.
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The problem of antiepileptic drug interactions is significant in that many epileptic patients are treated with multiple drug therapy. Moreover, patients may also be receiving additional medication for other concurrent disorders. Most drug interactions are pharmacokinetic, involving changes in absorption, protein binding, metabolism, or excretion. As a result, plasma levels of the antiepileptic drug may decrease leading to exacerbation of seizures. Alternatively, plasma levels may rise resulting in toxic side effects. Similar changes may also occur with drugs given for other disorders. In this paper, possible mechanisms of drug interactions are discussed. This is followed by a description of clinically significant interactions involving phenytoin, carbamazepine, barbiturates, valproic acid, benzodiazepines, and succinimides. Potentially serious drug interactions may be minimized by using as few medications as possible and by regularly monitoring plasma levels of antiepileptic drugs.
Monotherapy with one drug chosen out of basic anti-epileptic agents was carried out in 312 patients, including 2/3 of cases resistant to the drugs. Group A consisted of 110 patients treated with a single drug since the onset of the disease whereas group B consisted of 202 patients in whom polytherapy was reduced to monotherapy. The best results were achieved in patients of group A with short and medium duration of the disease. The results noted in patients of group B were worse and independent of the duration of epilepsy. The most favourable effects were noted in children with mild epilepsy and generalized epilepsy of unknown post-traumatic etiology. The results of monotherapy in focal seizures and epilepsy with organic lesions were markedly worse. The most effective drugs in this population were: barbiturates, valproic acid derivatives, and carbamazepine. The authors stress that all forms of epilepsy, especially newly diagnosed and previously untreated cases, should be treated with single agent.
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The effects have been investigated of anesthetic and convulsant barbiturates on the spontaneous and potassium-stimulated efflux of [3H]D-aspartate from rat cortex minislices. In concentrations (100 microM) which have previously been shown to alter calcium ATPase activity in synaptosomes, anaesthetic barbiturates depressed and convulsant barbiturates stimulated the spontaneous efflux of [3H]D-aspartate in a dose-dependent manner. The effects on the efflux of [3H]D-aspartate evoked by 44.7 mM KCl were similar, although one convulsant barbiturate (1,3M1B) was without effect. The results are discussed in terms of entry and removal of calcium ions from nerve terminals.
Ischaemic brain damage can follow global cerebral hypoxia, localized cerebral hypoxia and global cerebral anoxia as it occurs after circulatory arrest. The calcium-ion-mediated mechanism is one of the main routes to cerebral deterioration. Barbiturates are restricted for treatment of increased intracranial pressure and seizures. Calcium channel blockers cannot yet be recommended. Therapy remains mainly symptomatic. Hyperglycaemia should be avoided.
We studied the effect of a mixture containing branched-chain amino acids and taurine on the pool of free amino acids and their derivatives during chronic phenobarbital poisoning. Subchronic barbiturate poisoning produced by daily intraperitoneal injection of phenobarbital caused imbalance in the content of some amino acids in blood plasma and liver of rats. Treatment with the mixture of branched-chain amino acids and taurine normalized the content of amino acids in the liver and blood plasma of animals with subchronic phenobarbital poisoning. The mixture of branched-chain amino acids and taurine corrects metabolic processes and normalized the peripheral pool of amino acids. Our findings extend the range for application of amino acids in clinical practice.
Complementary hydrogen-bonding interactions between a barbituric acid-substituted fullerene derivative (1) and corresponding receptor (2) bearing thienylenevinylene units are used to assemble a 1:1 supramolecular complex (K = 5500 M(-1)). Due to the close proximity of the redox-active moieties within the assembly, strong ground-state electron-donor-acceptor interactions are observed. Photoinduced electron transfer from electron-rich thienylenevinylene subunits to the fullerene is very fast (k(et) = 5.5 x 10(12) s(-1)), as determined by fs-time-resolved transient absorption spectroscopy. [reaction: see text]
A number of treatment options are currently available for the medical management of epilepsy. Conventional antiepileptic drugs (AEDs) include phenytoin, carbamazepine, valproic acid, ethosuximide, barbiturates, and benzodiazepines. Although these drugs control seizures, they may also cause blood dyscrasias, sedation, and cognitive impairment. Felbamate, gabapentin, lamotrigine, and vigabatrin are new AEDs believed to cause fewer side effects than conventional medications. Felbamate, however, has been linked with substantially increased incidence of aplastic anemia, and the other new AEDs have been studied for relatively short periods of time. Ketogenic diets, comprised of foods high in fat and low in protein and carbohydrate content, have been reported to improve seizure control. However, these diets are widely acknowledged to be unpalatable, making sustained compliance with dietary restrictions difficult. To promote long-term control of seizures, physicians must consider the side effects of therapeutic interventions for epilepsy, as well as their anticonvulsant efficacy.