Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Agonists acting at subtypes of glutamate receptors, N-methyl-D-aspartate, kainate and quisqualate, induce convulsions in rodents. Clonic seizures induced in mice by intracerebral administration of N-methyl-D-aspartate, kainate or quisqualate were used to study the anti- and proconvulsant potential of antiepileptic drugs and beta-carbolines. Systemic administration showed that the benzodiazepines clonazepam and midazolam blocked convulsions induced by kainate and had no effect on seizures triggered by N-methyl-D-aspartate and quisqualate. In contrast, diazepam blocked convulsions induced by either excitatory amino acid, as did valproate. The benzodiazepine receptor agonist beta-carboline ZK 93423 blocked convulsions induced by kainate but had no effect on seizures induced by N-methyl-D-aspartate or quisqualate. The antagonist beta-carboline ZK 93426 did not affect convulsions induced by excitatory amino acids, while the inverse agonists FG 7142 and ethyl-beta-carboline-3-carboxylate increased the sensitivity of mice to kainate. Phenobarbital and 2-chloroadenosine protected mice against seizures induced by quisqualate and kainate, while baclofen was active against convulsions produced by kainate. MK-801 selectively blocked convulsions induced by N-methyl-D-aspartate, and enhanced the susceptibility of mice to seizures triggered by kainate and quisqualate. Ethosuximide increased the susceptibility of mice to N-methyl-D-aspartate and had little or no effect on other types of seizures. Diphenylhydantoin enhanced the convulsant potential of quisqualate. Trimethadione and carbamazepine did not affect convulsions induced by N-methyl-D-aspartate, kainate or quisqualate. Intracerebral administration of midazolam protected mice against seizures induced by kainate. Ethosuximide increased the susceptibility of mice to N-methyl-D-aspartate, while diphenylhydantoin to quisqualate convulsions.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Differential effects of antiepileptic drugs and beta-carbolines on seizures induced by excitatory amino acids. 209 26

Status epilepticus (SE) evolves through several stages when untreated. The later stages of SE are less responsive to standard anticonvulsants and may require general anesthesia to suppress seizures. Antagonists acting at the N-methyl-D-aspartate (NMDA) subclass of glutamate (excitatory) receptors have been demonstrated to exert antiepileptic activity in some seizure models. We report experiments performed to determine if NMDA receptor antagonists are effective in stopping seizures in the late stages of SE. A model of limbic SE induced by 90 min of 'continuous' electrical stimulation of the hippocampus in rats was employed. Three NMDA receptor antagonists, one 'competitive' (CPP) and two 'non-competitive' (ketamine and MK-801), were compared to 3 standard antiepileptic drugs (diazepam, phenobarbital, and phenytoin) for their ability to suppress seizures at a physiologically defined stage of SE. All NMDA receptor antagonists, diazepam and phenobarbital were effective in suppressing behavioral and electrographic seizures for varying periods of time. Phenytoin had no effect on SE. Ketamine and MK-801 induced a paradoxical enhancement of electrographic seizures that preceded SE suppression. We believe that NMDA-receptor antagonists offer a novel approach for treating the late stages of SE.
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PMID:NMDA receptor antagonists and limbic status epilepticus: a comparison with standard anticonvulsants. 216 58

The cholinergic agonist pilocarpine triggers sustained limbic seizures in rodents. Pilocarpine seizures were blocked by systemic administration of benzodiazepines, barbiturates, valproate and trimethadione, while diphenylhydantoin did not affect, and ethosuximide increased the susceptibility of rats to such seizures. This pattern of action of antiepileptic drugs is characteristic for pilocarpine seizures and different from other rodent models of epilepsy. Although the anatomical substrates in the forebrain involved in the expression of anticonvulsant activity are unknown, the basal ganglia are believed to be essential for the motor expression of pilocarpine seizures. Bilateral microinjections into the substantia nigra, a major output station of the basal ganglia, of midazolam (ED50 38.5 nmol; range 29-52 nmol), phenobarbital (ED50 16 nmol; range 7-39 nmol) and trimethadione (ED50 30 nmol; range 16-56 nmol) protected rats against pilocarpine seizures (380 mg/kg i.p.) Diphenylhydantoin (up to 100 nmol) remained inactive, while ethosuximide (ED50 38 nmol; range 22-65.5 nmol) reduced the threshold for pilocarpine seizures, converting subconvulsant doses of pilocarpine (200 mg/kg i.p.) into convulsant ones. The profiles of action of antiepileptic drugs on pilocarpine seizures were similar following intranigral and systemic administration. These observations suggest that the substantia nigra may mediate some actions of antiepileptic drugs.
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PMID:Substantia nigra regulates action of antiepileptic drugs. 220 34

In May 1988 a Therapeutic Drug Monitoring (TDM) service for anti-epileptic drugs was established at Prince Mshiyeni Memorial Hospital. This service was offered as a multidisciplinary team approach involving sisters, doctors, social workers and pharmacists at an epilepsy clinic. Statistics gathered over a 13-month period showed that: (i) epileptic patient numbers increased from 52 to 211 per 4-week cycle, while patients requiring TDM decreased from 40 to 20 per cycle; (ii) phenytoin was the most frequently prescribed anticonvulsant, followed by carbamazepine and phenobarbitone, throughout the period; (iii) TDM did not alter prescribing patterns--approximately 90% of patients were on monotherapy at the beginning and at the end of the assessment period; (iv) 471 serum levels were measured in 280 patients over 13 months. Phenytoin serum levels constituted the majority (53%) followed by carbamazepine (33%), phenobarbitone (12%) and valproate (2%); (v) of the levels measured in 24 patients taking phenytoin 300 mg/d who were experiencing neither seizures nor side-effects, 38% of levels were in the potentially toxic range; and (vi) well-controlled patients increased from 36% in the first cycle to 60% in the last cycle. A TDM service is very useful in a Third-World setting and can assist in conserving scarce sources provided it is utilised within a holistic treatment framework.
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PMID:The relevance of a First-World therapeutic drug monitoring service to the treatment of epilepsy in Third-World conditions. 224 92

During hyperthyroidism, hypothyroidism, and severe stress there is often an inverse relationship between plasma norepinephrine (NE) and thyroid hormones. We evaluated this relationship in patients who were severely burned, patients who had injury to both brain and body, patients with head injury, and patients receiving high dose barbiturates for head injury. Head-injured patients had a low thyroxine (T4), low triiodothyronine (T3), and high reverse T3. Phenytoin for control of seizures lowered T3 and T4 and increased thyroid-stimulating hormone. Burned patients had a strong negative correlation between NE and T3 (r = -.88, p less than .001). Patients with injury to both brain and body had a weak negative correlation between NE and T3 (r = -.5, p = .06). Patients with head injury showed no correlation between NE and T3. Severely injured patients had a close inverse relationship between elevated NE levels and depressed T3 levels. This relationship appears to depend on an intact CNS, as the relationship was disrupted by head injury and barbiturates.
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PMID:Catecholamine and thyroid hormones in traumatic injury. 230 47

Sodium phenobarbitone (20 and 70 mg/kg) had a significant anticonvulsant action against pentylenetetrazole-induced seizures, which persisted for 21 days of treatment. On drug withdrawal there was a significant decrease in seizure threshold below control level 24-48 h after the last dose of 70 mg/kg. Phenytoin (40 mg/kg) had a significant anticonvulsant action after 7 days of treatment and this persisted for 21 days of treatment. On drug withdrawal there was a significant decrease in seizure threshold 48 h after the last dose. Lorazepam (0.1 mg/kg) had a significant anticonvulsant action, but the group tested after 21 days of treatment did not differ from the controls, indicating that tolerance had developed to this effect; on drug withdrawal there was a decrease in seizure threshold from 24 to 72 h. The only drug to increase aggressive behaviour was sodium phenobarbitone (70 mg/kg); this reached significance after 14 and 21 days of treatment and occurred 8 h after drug administration; 0.5 h after drug administration phenobarbitone (70 mg/kg) abolished aggressive behaviour. After 7 days of treatment phenobarbitone (70 mg/kg) increased social behaviour 0.5 h after administration and this was still increased after 21 days of treatment. On drug withdrawal, there were no changes in aggressive behaviour, but there were significant decreases in social behaviour 24 and 48 h after phenobarbitone (70 mg/kg) withdrawal and 24, 48 and 72 h after lorazepam (0.1 mg/kg) withdrawal.
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PMID:Changes in seizure threshold and aggression during chronic treatment with three anticonvulsants and on drug withdrawal. 230 12

Among 630 patients with human immunodeficiency virus infection, 70 patients with new-onset seizures were studied. Generalized seizures occurred in 66 patients (94%): they occurred as the initial seizure in 56 patients (80%) and during follow-up in another 10 patients (14%). Partial seizures (18 patients), status epilepticus (10 patients), and recurrent seizures (38 patients) were also noted. Identified processes included cerebral toxoplasmosis in 11 patients, cerebral lymphoma in 8, metabolic derangement in 8, cryptococcal meningitis in 7, and vascular infarction in 4. In 32 patients (46%) seizures were not associated with identifiable brain lesions and were believed to result from human immunodeficiency virus cerebral infection. Phenytoin treatment was associated with adverse drug reactions in 16 of 62 patients who received it. Our results suggest that the majority of patients with human immunodeficiency virus and seizures do not have secondary focal brain lesions as the cause of the seizures and that human immunodeficiency virus infection alone can, and often does, cause seizures.
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PMID:Seizures in human immunodeficiency virus infection. 234 90

The pharmacokinetic profile of a newly developed Dilantin 300-mg Kapseal formulation was compared with that of currently marketed Dilantin 100-mg Kapseals in both a 300-mg single-dose bioequivalence study in nine healthy volunteers and a once-daily 300-mg multiple-dose study in 18 patients with seizures. Results of these studies indicate the rate and extent of absorption of the 300-mg extended phenytoin (PHT) sodium capsule formulation are similar to that of 100-mg extended PHT sodium capsules based on PHT plasma maximum concentrations and time to achieve them (Cmax, tmax), and area under the curve (AUC) values and the urinary excretion of total hydroxy phenylhydantoin (HPPH) in the single-dose study and steady-state PHT plasma Cmax, tmax, minimum plasma concentrations (Cmin), and AUC values and urinary excretion of total HPPH in the multiple-dose study. Control of seizures in patients was equally maintained on a once-daily 300-mg multiple-dosing regimen administered as either one 300-mg extended PHT sodium capsule daily or three 100-mg extended PHT sodium capsules daily. Therefore, 300-mg extended PHT sodium capsules can be safely and effectively interchanged with three 100-mg extended PHT sodium capsules in patients requiring a once-daily 300-mg PHT sodium dosing regimen.
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PMID:Pharmacokinetic profile of a 300-mg extended phenytoin sodium capsule (Dilantin) formulation. 236 80

The effects of clinically used anticonvulsant drugs on high-frequency sustained repetitive firing (SRF) of action potentials and on postsynaptic responses to iontophoretically applied gamma-aminobutyric acid (GABA) have been compared to establish a classification of anticonvulsant drugs based on cellular mechanisms of action. By using concentrations in the range of therapeutic cerebrospinal fluid values in humans, drugs have been separated into three categories: Phenytoin, carbamazepine, and valproic acid limited SRF, but did not alter GABA responses. Phenobarbital, clonazepam, and diazepam augmented GABA responses and limited SRF only at concentrations above the therapeutic range in ambulatory patients but that are achieved in the acute treatment of status epilepticus. Ethosuximide failed to affect SRF or GABA responses even at supratherapeutic concentrations. Ability of an anticonvulsant to limit SRF correlated well with efficacy against generalized tonic-clonic seizures clinically and against maximal electroshock seizures in experimental animals. Augmentation of GABA responses and lack of limitation of SRF correlated with efficacy against generalized absence seizures in humans and against pentylenetetrazol-induced seizures in animals. However, ethosuximide must act against generalized absence seizures and against pentylenetetrazol-induced seizures by a third, as yet unknown, mechanism. Other actions occurring at supratherapeutic concentrations correlated with clinical toxicity.
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PMID:Anticonvulsant drug mechanisms of action. 240 25

Phenytoin is a major anticonvulsant drug that is very effective in controlling a wide variety of seizure disorders while impairing neurological function little, if at all. Early work suggested the hypothesis that the drug's effects were due to a selective block of high-frequency neuronal activity. This theory is reevaluated in the light of accumulated observations on the effects of phenytoin in many neuronal and synaptic preparations. Most of these observations can be explained by a use- and frequency-dependent suppression of the sodium action potential by phenytoin, with a consequent filtering out of sustained high-frequency neuronal discharges and synaptic activity. The molecular mechanism for this is a voltage-dependent blockade of membrane sodium channels responsible for the action potential. Through this action, phenytoin obstructs the positive feedback that underlies the development of maximal seizure activity, while normal brain activity, proceeding at lower neuronal firing rates, is spared its depressant action. Other mechanisms of action that may contribute to the drug's efficacy and selectivity are also discussed.
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PMID:Phenytoin: mechanisms of its anticonvulsant action. 242 83


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