Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Valproic acid is a new antiepileptic drug. It has a marked effect on generalized spike-wave discharges. The exact mechanism of action is uncertain; however, some evidence suggests an effect on the metabolism of gamma-aminobutyric acid. It is rapidly absorbed from the gastrointestinal (GI) tract. Concurrent administration with phenobarbital may result in elevated phenobarbital plasma concentrations. Administration with phenytoin sodium may transiently result in lower total phenytoin plasma levels. Side effects are generally mild and include fatigue, GI disturbances, weight gain, a fine postural and resting tremor, mild thrombocytopenia, and an increase in hepatic enzymes. Platelet counts and liver function monitoring should be done during valproic acid therapy. Drowsiness may be seen in patients receiving other antiepileptic drugs concurrently.
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PMID:Valproic acid. Review of a new antiepileptic drug. 11 Feb 94

Development of the fatigue state in rats, subjected to prolonged alcohol intoxication, after swimming with might led to dissimilar alterations in the system of ammonia formation and binding in brain and spinal cord as compared with control animals under the same conditions of loading. Within the first minutes of the heavy loading the faster and more distinct accumulation of ammonia was observed, then the rapid exhaustion of the reaction occurred and the ammonia production was markedly decreased in the state of fatigue. Impairments in brain protein deamidation and decrease in content of urea were found. At the same time, dynamics of gamma-aminobutyric acid, dicarboxylic amino acids and their amides was altered.
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PMID:[Brain and spinal cord nitrogen metabolism in chronic alcoholism following strenuous physical exertion]. 719 7

Tiagabine is a new antiepileptic drug which acts by a novel mechanism, inhibiting the reuptake of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) into neurons and glia. A double-blind, placebo-controlled, crossover trial was undertaken, based upon a response-dependent design. Ninety-four patients with complex partial seizures with or without secondary generalised tonic-clonic seizures were recruited into an open screening phase and tiagabine was added to their existing drug therapy in doses titrated to reduce seizure frequency by > or = 25% or to the limit of tolerance. Forty-six responders were subsequently randomised to a double-blind crossover trial in which tiagabine was compared with placebo. Forty-two patients completed the trial. A significant reduction in the frequency of complex partial and secondary generalised tonic clonic seizures was seen. Twenty-six percent had a reduction of > or = 50% in the frequency of their complex partial seizures, and of the 27 patients who also had secondary generalised tonic clonic seizures, 63% experienced a reduction of > or = 50%. No interactions with baseline antiepileptic drugs were detected and no serious adverse reactions occurred. The commonest adverse events were tiredness, dizziness and headache. We conclude that tiagabine has promising antiepileptic effects. Further trials are underway.
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PMID:Adjunctive treatment of partial seizures with tiagabine: a placebo-controlled trial. 764 74

Gabapentin is an antiepileptic drug with an unknown mechanism of action apparently dissimilar to that of other antiepileptic agents, and possessing some desirable pharmacokinetic traits. The drug is not protein bound, is not metabolised and does not induce liver enzymes, diminishing the likelihood of drug interactions with other antiepileptic agents and drugs such as oral contraceptives. Although gabapentin is a structural analogue of the neurotransmitter gamma-aminobutyric acid (GABA), which does not cross the blood-brain barrier, gabapentin penetrates into the CNS and its activity is seemingly distinct from GABA-related effects. Present clinical evaluation is largely restricted to proof of efficacy trials of gabapentin as add-on therapy in patients with partial epilepsy resistant to conventional treatment. Gabapentin (usually 600 to 1800 mg/day) provides notable benefit, reducing seizure frequency by > or = 50% in 18 to 28% of patients with refractory partial seizures, as shown in 3 double-blind, placebo-controlled trials. Overall, seizure frequency decreased by 18 to 32% during 3-month treatment periods. Patients with complex partial seizures, and partial seizures secondarily generalised, are particularly likely to respond to gabapentin. Current experience with the drug in other seizure types, and as monotherapy, is limited. Mild adverse events, commonly somnolence, fatigue, ataxia and dizziness, have been reported in about 75% of gabapentin recipients. While the drug has been well tolerated when administered to a few patients for periods of up to 5 years, its long term tolerability profile has yet to be fully expounded. Thus, with its favourable pharmacokinetic profile, and efficacy in some refractory patients, gabapentin is poised to fill a niche as an adjunct to the treatment of partial epilepsy. Promising results obtained thus far warrant further work to clarify its long term tolerability, its possible efficacy in other seizure types, its position relative to other agents and its use as monotherapy. In the meantime, gabapentin is likely to provide a much-needed option in a therapeutic area requiring complex management.
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PMID:Gabapentin. A review of its pharmacological properties and clinical potential in epilepsy. 769 32

Vigabatrin was designed to increase the levels of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) in the brain. It does this by replacing GABA as a substrate for the action of the catabolic enzyme GABA-transaminase. As a result of this inhibition, neuronal GABA levels are elevated, resulting in enhanced endogenous GABA transmission. A number of clinical trials assessing the effect of vigabatrin in epilepsy have been completed. Vigabatrin is of proven benefit in partial seizures and secondarily generalised tonic clonic seizures, and it is licensed for use as adjunctive therapy in these conditions in several European countries. It has been shown to be effective in some epilepsy syndromes in children including West's syndrome, infantile spasms and cryptogenic partial seizures. Its effect on primary generalised tonic clonic seizures is variable, while there is considerable evidence that it has a deleterious effect on myoclonic and absence seizures. There have been a few reports of the benefits of vigabatrin in other neurological disorders including tardive dyskinesia, degenerative ataxias and GABA metabolism disorders. The adverse effects associated with vigabatrin are similar to those seen with other anticonvulsants, with a predominance of CNS effects including somnolence, fatigue, irritability, dizziness and headache. Psychiatric symptoms including depression and psychosis are seen in a small number of patients and cause the most problems. These often necessitate discontinuation of vigabatrin, which usually results in resolution of symptoms.
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PMID:A risk-benefit assessment of vigabatrin in the treatment of neurological disorders. 803 89

We have investigated the regulation of an N-methyl-D-aspartate (NMDA) receptor-mediated synaptic potential by gamma-aminobutyric acid (GABA)-mediated inhibition using extracellular and whole-cell voltage clamp recordings in rat auditory cortex in vitro. Single afferent stimulus pulses at low intensity elicited a slow extracellular negativity (Component C) that was mediated by NMDA receptors. At higher intensities, Component C was suppressed by recruitment of GABAergic inhibition. To understand the actions of GABAergic inhibition on Component C, we determined the effects of: (i) paired-pulse stimulation, which depresses GABAergic inhibition; (ii) pharmacological antagonism of GABA receptors; and (iii) afferent stimulation in slices from neonatal rats prior to the development of cortical inhibition. The results indicate that GABAergic inhibition prevents Component C from occurring, thereby preventing its reduction upon repeated stimulation. Whole-cell voltage clamp recordings were used to test the hypothesis that GABAergic suppression occurred by way of membrane hyperpolarization. At hyperpolarized holding potentials no NMDA receptor-mediated synaptic current was elicited, even with paired-pulse stimulation. At depolarized holding potentials a significant NMDA synaptic current was elicited despite the presence of GABAergic synaptic currents. We conclude that membrane hyperpolarization by GABAergic inhibition prevents the appearance and subsequent fatigue of an NMDA receptor-mediated synaptic potential. Reduction of inhibition can act as a 'switch' to fully release the NMDA potential as frequently as once every 10-20 s.
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PMID:GABAergic suppression prevents the appearance and subsequent fatigue of an NMDA receptor-mediated potential in neocortex. 861 25

The mechanism of prolongation of sleeping (anesthesia) time after phenobarbital (PB) treatment was assessed in mice with ethionine (ET)-induced liver disorders (ET-treated group). The brain gamma-aminobutyric acid (GABA), glutamic acid (GLU), lactic acid (LA), and pyruvic acid (PA) levels were significantly higher in the ET-treated group than the control group. The ET-treated group showed an abnormal neurotransmission and a decrease in energy metabolism. After administration of PB (175 mg/kg, i.p.), sleeping time and the brain GABA, GLU, LA, PA, and PB levels at the awakening point were compared between ET-treated and control groups. Sleeping time in the ET-treated group was two times longer than that in the control group. At the awakening point, the brain GABA and LA levels in the ET-treated and control groups and the PA level in the ET-treated group were significantly lower than those without PB treatment; and the GLU level in the ET-treated group was significantly higher than that without PB treatment. The brain concentrations of PB in both groups remained the same for seven hr after PB treatment. There was no difference in the brain PB concentration between the two groups at the awakening point, although the ET-treated group showed impairment of excretion of PB at 18 hr of PB treatment. In conclusion, awakening is not directly correlated with a decrease in PB in the brain, but rather to changes in the brain GABA, GLU, and other substances, and an inhibition of the neurotransmission and decreased energy metabolism in the brain are considered to be involved in the prolongation of PB-induced sleeping time in the ET-treated mice.
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PMID:Sleeping time after phenobarbital treatment and the brain levels of gamma-aminobutyric acid and phenobarbital at the regaining of righting response point in ethionine-induced liver-disordered mice. 878 Sep 95

The aim of this study was to investigate if enhanced peripheral ammonia production during exhaustive exercise increases ammonia detoxication in brain mediated by glutamine synthesis, and subsequently influences glutamate and gamma-aminobutyric acid (GABA) levels. This neurotransmitter production is related to the metabolism of glutamine. A group of rats was trained for 6 weeks by treadmill running (TR). They were compared to a group of untrained rats (UN). At the end of training, half of TR and UN rats were submitted to one session of treadmill running until exhaustion (288+/-12 min and 62+/-5 min in TR and UN group, respectively). At exhaustion, running and control rats were sacrificed in order to collect blood and to take samples of the following brain structures: cortex, striatum and cerebellum. Treadmill running until exhaustion induced an increase in blood ammonia by 140% without significant differences between TR and UN groups. Brain ammonia increased in both groups. However, TR group exhibited values 50% higher than those observed in UN group. Brain glutamine was increased at exhaustion in all groups of running rats by 30-75% of basal value whereas the glutamate only decreased in TR rats which were able to run for a longer time. In this group, the GABA level decreased in striatum. These data confirm that enhanced brain ammonia level during exercise stimulates glutamine synthesis as a mechanism of detoxication. After several hours of running, a reduction in brain glutamate levels was observed in all brain structures in trained rats but only in the striatum in untrained animals. The reduced availability of this GABA precursor decreases GABA levels only in the striatum of TR group by 45% of the resting value. These results suggest a relation between cerebral changes in neurotransmitters and excitatory amino acids, such as glutamate and GABA, and central fatigue.
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PMID:Effects of prolonged exercise on brain ammonia and amino acids. 972 Oct 55

Antiepileptic drugs (AEDs) have various mechanisms of actions and therefore have diverse anticonvulsant, psychiatric, and adverse effect profiles. Two global categories of AEDs are identified on the basis of their predominant psychotropic profiles. One group has "sedating" effects in association with fatigue, cognitive slowing, and weight gain, as well as possible anxiolytic and antimanic effects. These actions may be related to a predominance of potentiation of gamma-aminobutyric acid (GABA) inhibitory neurotransmission induced by drugs such as barbiturates, benzodiazepines, valproate, gabapentin, tiagabine, and vigabatrin. The other group is associated with predominant attenuation of glutamate excitatory neurotransmission and has "activating" effects, with activation, weight loss, and possibly anxiogenic and antidepressant effects. This group includes agents such as felbamate and lamotrigine. Agents such as topiramate, with both GABAergic and antiglutamatergic actions, may have "mixed" profiles. Mechanisms of actions, activity in animal models of anxiety and depression, and clinical psychotropic effects of AEDs in psychiatric and epilepsy patients are reviewed in relationship to this proposed categorization. These considerations suggest the testable hypothesis that better psychiatric outcomes in seizure disorder patients could be achieved by treating patients with baseline "activated" profiles (insomnia, agitation, anxiety, racing thoughts, weight loss) with "sedating" predominantly GABAergic drugs, and conversely those with baseline "sedated" or anergic profiles (hypersomnia, fatigue, apathy, depression, sluggish cognition, weight gain) with "activating" predominantly antiglutamatergic agents. Systematic clinical investigation of more precise relationships of discrete mechanisms of actions to psychotropic profiles of AEDs is needed to assess the utility of this general proposition and define exceptions to this broad principle.
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PMID:Positive and negative psychiatric effects of antiepileptic drugs in patients with seizure disorders. 1049 35

Auditory brainstem responses (ABRs) were recorded in 60 male or female, anxious or anxiety-free university students, before and after separated or simultaneous intake of alprazolam and exposure to noise. A significant increase of the latencies of the ABRs was found when subjects took alprazolam. This effect is consistent with the presence of gamma-aminobutyric acid (GABA), one of the neurotransmitters at terminals of cochlear efferent fibres A significant increase of the latencies was observed after noise alone. In subjects taking alprazolam when they are exposed to noise, the effect of noise on the ABR latencies is reduced, but not abolished. The effects of alprazolam on the ABR are consistent with the presence of GABA in the medulla and pons. Significant effects of noise upon III-V and I-V intervals suggest that auditory 'fatigue' may involve a retrocochlear component. Differences due to sex appear to be abolished by anxiety.
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PMID:Separate and combined effects of a benzodiazepine (alprazolam) and noise on auditory brainstem responses in man. 1058 32


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