Acute conduction velocity changes in guinea-pigs after administration of diphenylhydantoin. (1/836)

Motor nerve conduction velocity was measured after dosing guinea-pigs with 200-400 mumol/kg diphenylhydantoin (DPH) daily for three to four days. Conduction velocity fell by a mean value of 13% in animals that achieved plasma DPH levels over 200 mumol/l. There was no change in velocity with DPH levels below this value.  (+info)

Metabolism of daunorubicin by a barbiturate-sensitive aldehyde reductase from rat liver. (2/836)

A barbiturate-sensitive aldehyde reductase was purified to homogeneity from rat liver and shown to metabolize the cancer-chemotherapeutic antibiotic daunorubicin. The aldehyde reductase may have important roles in the metabolism of exogeneous drugs as well as the aldehyde derivatives of the biogenic amines.  (+info)

Does withdrawal of different antiepileptic drugs have different effects on seizure recurrence? Further results from the MRC Antiepileptic Drug Withdrawal Study. (3/836)

One thousand and thirteen patients, in remission of epilepsy for at least 2 years, were randomized to continued therapy or slow withdrawal over 6 months and were followed up for a median period of 5 years. At the time of randomization 83% of patients were receiving monotherapy with carbamazepine (237 patients), phenobarbitone/primidone (72 patients), phenytoin (184 patients) or valproate (228 patients) in low doses, and plasma levels were below the usual optimal range. The most important factor determining seizure recurrence was continued therapy, which was the case for barbiturates, phenytoin and valproate. There was no significant difference for patients taking carbamazepine at randomization, because of a low rate of recurrence in those withdrawing treatment. The difference between carbamazepine and other drugs was not explained by differences in covariate prognostic factors. There was no evidence that withdrawal of phenobarbitone was associated with withdrawal seizures. These data provide unique evidence for the effectiveness of standard antiepileptic drugs as monotherapy. The results for carbamazepine may be open to a number of interpretations.  (+info)

Neuromyotonia: an unusual presentation of intrathoracic malignancy. (4/836)

A 48 year old woman is described who presented with increasing muscular rigidity and who was found to have a mediastinal tumour. Electrophysiological studies revealed that the muscular stiffness resulted from very high frequency motor unit activity which outlasted voluntary effort, and which was abolished by nerve block. The abnormal activity may have arisen at the anterior horn cell level. Marked improvement followed the administration of diphenylhydantoin.  (+info)

Anticonvulsant-induced dyskinesias: a comparison with dyskinesias induced by neuroleptics. (5/836)

Anticonvulsants cause dyskinesias more commonly than has been appreciated. Diphenylhydantoin (DPH), carbamazepine, primidone, and phenobarbitone may cause asterixis. DPH, but not other anticonvulsants, may cause orofacial dyskinesias, limb chorea, and dystonia in intoxicated patients. These dyskinesias are similar to those caused by neuroleptic drugs and may be related to dopamine antagonistic properties possessed by DPH.  (+info)

An in vitro electrophysiological study on the effects of phenytoin, lamotrigine and gabapentin on striatal neurons. (6/836)

We performed intracellular recordings from a rat corticostriatal slice preparation in order to compare the electrophysiological effects of the classical antiepileptic drug (AED) phenytoin (PHT) and the new AEDs lamotrigine (LTG) and gabapentin (GBP) on striatal neurons. PHT, LTG and GBP affected neither the resting membrane potential nor the input resistance/membrane conductance of the recorded cells. In contrast, these agents depressed in a dose-dependent and reversible manner the current-evoked repetitive firing discharge. These AEDs also reduced the amplitude of glutamatergic excitatory postsynaptic potentials (EPSPs) evoked by cortical stimulation. However, substantial pharmacological differences between these drugs were found. PHT was the most effective and potent agent in reducing sustained repetitive firing of action potentials, whereas LTG and GBP preferentially inhibited corticostriatal excitatory transmission. Concentrations of LTG and GBP effective in reducing EPSPs, in fact, produced only a slight inhibition of the firing activity of these cells. LTG, but not PHT and GBP, depressed cortically-evoked EPSPs increasing paired-pulse facilitation (PPF) of synaptic transmission, suggesting that a presynaptic site of action was implicated in the effect of this drug. Accordingly, PHT and GBP, but not LTG reduced the membrane depolarizations induced by exogenously-applied glutamate, suggesting that these drugs preferentially reduce postsynaptic sensitivity to glutamate released from corticostriatal terminals. These data indicate that in the striatum PHT, LTG and GBP decrease neuronal excitability by modulating multiple sites of action. The preferential modulation of excitatory synaptic transmission may represent the cellular substrate for the therapeutic effects of new AEDs whose use may be potentially extended to the therapy of neurodegenerative diseases involving the basal ganglia.  (+info)

A generalized seizure following initiation of nelfinavir in a patient with human immunodeficiency virus type 1 infection, suspected due to interaction between nelfinavir and phenytoin. (7/836)

Nelfinavir, one of human immunodeficiency virus (HIV) specific protease inhibitors(PIs), is widely used for the treatment of HIV infection. Nelfinavir, which is metabolized with the cytochrome p450 isoforms, elevate the phenytoin level theoretically because nelfinavir acts as an inhibitor of phenytoin metabolism through the enzyme. However, we encountered a case of seizure recurrence caused by a lowered phenytoin level after initiation of nelfinavir. We should be aware of the change in the phenytoin level in concomitant use of nelfinavir.  (+info)

Falsely increased immunoassay measurements of total and unbound phenytoin in critically ill uremic patients receiving fosphenytoin. (8/836)

BACKGROUND: Fosphenytoin, a phosphate ester prodrug of phenytoin, is metabolized to phenytoin in vivo. Phenytoin metabolites accumulate in renal insufficiency and cross-react in some phenytoin immunoassays. Our aim was to determine the accuracy of phenytoin immunoassays in renal patients treated with fosphenytoin. METHODS: We measured phenytoin with HPLC and with the aca, ACS:180, TDx phenytoin II, Vitros, and AxSYM methods. Specimens were collected 2-120 h after fosphenytoin administration from 17 patients with renal insufficiency. RESULTS: The AxSYM, TDx phenytoin II, ACS:180, and Vitros assays displayed falsely increased phenytoin results up to 20 times higher than the HPLC results. The aca Star results for these specimens were comparable to the HPLC results. Although fosphenytoin can cross-react with phenytoin immunoassays, no fosphenytoin was detected by a sensitive HPLC method in any sample that was tested for its presence. CONCLUSION: These results are consistent with the formation of one or more novel metabolites or adducts of fosphenytoin that accumulate in some critically ill patients with renal insufficiency and that display significant cross-reactivity with some, but not all, phenytoin immunoassay methods.  (+info)