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J Adín

Publications and source records attributed to J Adín.

8 recordsLinked to original sources
PubMed2005

Ion channels and epilepsy.

The role of voltage-gated and ligand-gated ion channels in epileptogenesis of both genetic and acquired epilepsies, and as targets in the development of new antiepileptic drugs (AEDs) is reviewed. Voltage-gated Na+ channels are essential for action potentials, and their mutations are the substrate for generalised epilepsy with febrile seizures plus and benign familial neonatal infantile seizures; Na+ channel inhibition is the primary mechanism of carbamazepine, phenytoin and lamotrigine, and is a probable mechanism for many other classic and novel AEDs. Voltage-gated K+ channels are essential in the repolarisation and hyperpolarisation that follows paroxysmal depolarisation shifts (PDSs), and their mutations are the substrate for the benign neonatal epilepsy and episodic ataxia type 1; they are new targets for AEDs such as retigabine. Voltage-gated Ca2+ channels are involved in neurotransmitter release, in the sustained depolarisation-phase of PDSs, and in the generation of absence seizures; their mutations are a substrate for juvenile myoclonic epilepsy and the absence-like pattern seen in some mice; the antiabsence effect of ethosuximide is due to the inhibition of thalamic T-type Ca2+ channels. Voltage-gated Cl- channels are implicated in GABA(A) transmission, and mutations in these channels have been described in some families with juvenile myoclonic epilepsies, epilepsy with grand mal seizures on awakening or juvenile absence epilepsy. Hyperpolarisation-activated cation channels have been implicated in spike-wave seizures and in hippocampal epileptiform discharges. The Cl- ionophore of the GABA(A) receptor is responsible for the rapid post-PDS hyperpolarisation, it has been involved in epileptogenesis both in animals and humans, and mutations in these receptors have been found in families with juvenile myoclonic epilepsy or generalised epilepsy with febrile seizures plus; enhancement of GABA(A) inhibitory transmission is the primary mechanism of benzodiazepines and phenobarbital and is a mechanistic approach to the development of novel AEDs such as tiagabine or vigabatrin. Altered GABA(B)-receptor function is implicated in spike-wave seizures. Ionotropic glutamate receptors are implicated in the sustained depolarisation phase of PDS and in epileptogenesis both in animals and humans; felbamate, phenobarbital and topiramate block these receptors, and attenuation of glutamatergic excitatory transmission is another new mechanistic approach. Mutations in the nicotinic acetylcholine receptor are the substrates for the nocturnal frontal lobe epilepsy. The knowledge of the role of the ion channels in the epilepsies is allowing the design of new and more specific therapeutic strategies.

Action Potentials↗
PubMed2000

[Ion channels and epilepsy].

OBJECTIVE: We review the role of ligand-gated ion channels and voltage-gated ion channels as a substrate for the epileptogenesis and as targets in the development of new antiepileptic drugs. DEVELOPMENT: Voltage-gated calcium channels are involved in the release of neurotransmitters, in the sustained depolarization-phase of paroxysmal depolarisation shifts (PDS), and in the generation of absences; they are also the genetic substrate of generalized tonic-clonic convulsions and absence-like pattern seen in some mice. The voltage-gated potassium channel has been implicated in the hyperpolarization-phase of PDS, it is the genetic substrate of the long QT syndrome, benign neonatal epilepsy, and episodic ataxia/myokymia syndrome, and it is the target of some antiepileptic drugs which activate this channel. The voltage-gated sodium channel is the target of most of the classical and newer antiepileptic drugs; it is also the substrate for generalized epilepsy with febrile seizures plus. The sodium channel of the nicotinic acetylcholine receptor is the substrate for nocturnal frontal lobe epilepsy. The sodium channels of the AMPA and KA glutamate receptors have been proposed as substrate for juvenile absence epilepsy and are a target for new antiepileptic drugs which inhibit it. The calcium channel of the NMDA glutamate receptor has been implicated in the sustained depolarization-phase of PDS and in epileptogenesis after kindling and is a main target for new antiglutamate drugs. The chloride channel of the GABAA receptor is responsible for the rapid hyperpolarization of PDS, it has been involved in epileptogenesis after kindling, it may be the substrate of the Angelman syndrome, and it is activated by many classical and new antiepileptic drugs. CONCLUSION: The knowledge of the role of the ion channels in the epilepsies is allowing the design of new and more specific therapeutic strategies.

Angelman Syndrome↗
PubMed2000

[Antiepileptic drugs and the liver].

OBJECTIVES: We review the metabolism of antiepileptic drugs with particular emphasis on the formation of active metabolites and toxic intermediate metabolites, together with the factors altering this and the possibility of interactions between the antiepileptic drugs themselves and with other drugs. DEVELOPMENT: Most antiepileptic drugs undergo complex metabolic processes in the liver which determine the time course of their concentration in the organism and therefore their therapeutic and toxic effects. Also, the processes by which drugs are metabolised may be influenced by many physiological and pathological factors, as well as the presence of other drugs which cause clinically relevant interactions. We analyze the function of the liver in the metabolism of these drugs with special reference to the microsome oxidation mediated by cytochrome P-450 and the glucuronidation catalysed by glucuronosyltransferase and the processes of enzyme induction and inhibition. Subsequently, we describe the metabolism of the antiepileptic drugs, their main routes of elimination, factors affecting this, role of the active and intermediate metabolites and the involvement of the enzyme induction and inhibition underlying the interactions of these drugs. Finally, we describe the metabolism of the most important classical and new antiepileptic drugs, the isoforms of cytochrome P-450 involved, the factors altering this and the most relevant interactions with other antiepileptic and non-antiepileptic drugs. CONCLUSION: Knowledge of the paths by which the antiepileptic drugs are metabolised, particularly the isoforms of cytochrome P-450 involved facilitates understanding of the influence of various factors on the metabolism of drugs, and also of their complex interactions.

Anticonvulsants↗
PubMedDate not supplied

[The use of intravenous valproate].

OBJECTIVE: To review the role of intravenous valproate (i.v. VPA) as an alternative to the oral route in the acute treatment of epileptic seizures and status epilepticus, and to establish criteria for its use. DEVELOPMENT: The bioavailability and tolerance of i.v. VPA, when administered in infusion for 60 minutes every 6 hours, are similar to those of oral VPA. Much of the data on acute administration, by injections of 3 to 5 minutes, for the treatment of seizures, are from series of cases and summaries from congresses and require confirmation. However, they suggest that i.v. VPA may be useful for the treatment of: a) convulsions due to insufficient blood drug levels or failure to take the drug, in order to rapidly raise the drug levels; b) a generalized convulsive status which is partially resistant to diazepam and phenytoin, as a non-depressant alternative to phenobarbital and other CNS depressants, and c) a non-convulsive status as an alternative to benzodiazepines when it is desired to avoid their side effects or when the treatment is going to be continued with oral VPA. The initial dose should be based on the concentration to be reached and the patient's previous VPA levels; the maintenance dose should be based on the stable level to be maintained, the age of the patient and the presence of enzyme inducers. CONCLUSION: Intravenous VPA would seem to offer new perspectives for the acute treatment of seizures, but its usefulness may be critically dependent on its correct use based on clinical and pharmacokinetic principles.

Adolescent↗
PubMedDate not supplied

[Pharmacological basis for withdrawal of antiepileptic drugs].

OBJECTIVE: To review the pharmacological basis for withdrawal of antiepileptic drugs: the mechanisms by which seizures reappear, aspects of treatment which affect relapses and procedures for withdrawal of medication. DEVELOPMENT: Antiepileptic drugs are not curative, so when they are withdrawn the natural course of the condition becomes evident. Reappearance of seizures may be due to lack of protection and/or an abstinence syndrome. Seizures due to lack of protection occur following withdrawal of any antiepileptic drug when the epilepsy is not cured; they may not reappear for years (although over 80% occur within a year) and treatment then has to be restarted. They seem to be less frequent after withdrawal of carbamazepine or phenytoin than after withdrawing valproate, although the reason for this is not understood. Seizures due to an abstinence syndrome only occur after withdrawing benzodiazepines, phenobarbitone and primidone; they are seen in patients with both active and inactive epilepsy whilst the drug is being withdrawn and tend to be self-limiting. It is not necessary to reintroduce the drug when epilepsy is cured. Felbamate and vigabatrin cause seizures related to their withdrawal, but the mechanism of this is not clear. There is no scientifically established guideline for withdrawing antiepileptic drugs, but it is considered important to stop one at a time, starting with those which may cause abstinence syndromes, followed by the more toxic, less effective antiepileptic drugs, which cause more drug interactions and are more awkward to take. CONCLUSION: Further specific studies are necessary to establish the mechanisms of relapses and the scientific basis for withdrawal of antiepileptic drugs.

Adult↗
PubMedDate not supplied

[Intranasal and buccal midazolam in the treatment of acute seizures].

AIMS: There are several personal and social problems involved in the administration of rectal diazepam that make it unsuitable for use in public places and by non medical workers, in children and especially in teenagers and adults. Intranasal and oral midazolam could be an alternative to rectal diazepam. We review the efficacy and safety of these ways of administering midazolam, which is already used in some countries as a sedative and as an anticonvulsive drug, despite the fact that it has not yet received authorisation. DEVELOPMENT: Intranasal midazolam (INM) was first used as a sedative in dental extractions, echocardiography, endoscopies or surgery, especially in children. After proving its efficacy electroencephalographically in patients with seizures, it started to be used to interrupt acute seizures. In three randomised trials, the efficacy of intranasal and oral midazolam in hospitalised patients was similar to, and even higher than, that of intravenous or rectal diazepam, with a similar speed of action and safety; no studies have been conducted, however, in the extra hospital milieu and its risk of respiratory depression may be like that of other benzodiazepines. One of the problems of using the parenteral solution for intranasal administration is the irritation that is produced by its acidic pH and the relatively large volume that has to be administered. These problems could be reduced by using aerosols containing a solution of midazolam in cyclodextrin, which accomplishes a greater concentration with a pH that is less acidic. Oral administration can be used in patients with nasal secretions or intense movements of the head. CONCLUSIONS: Intranasal or oral midazolam can improve the treatment of acute seizures in the hospital milieu and, more especially, in the extra hospital milieu when patients are attended by non medical staff. There is a need, however, for trials that prove its efficacy and safety in this situation.

Administration, Buccal↗
PubMedDate not supplied

[The interactions of antiepileptic drugs in oncology practice].

AIMS: Antiepileptic drugs, which often have to be used in patients with cancer, can have important effects on the results offered by antineoplastic agents. Here, we review the influence of antiepileptic drugs on antineoplastic agents and the influence of antineoplastic agents on antiepileptic drugs; measures to prevent such interactions are also suggested. DEVELOPMENT: Antiepileptic drugs that induce cytochrome P450, such as carbamazepine, phenytoin and phenobarbital, can reduce the levels and effects of antineoplastics that metabolise by means of this enzyme, for example, taxanes, Vinca alkaloids, methotrexate, teniposide and camptothecin. Furthermore, enzyme-inducing antiepileptic drugs diminish the levels and effects of many other drugs that can be administered to oncology patients, such as other antiepileptic drugs used in polytherapy, narcotic analgesics, antidepressants, antipsychotics or antibiotics. In contrast, valproate can increase the toxicity of etoposide or nitrosoureas. Moreover, antineoplastic agents like cisplatin or corticoids can lower the effectiveness of phenytoin and methotrexate has a similar effect on valproate. In contrast, 5-fluorouracil can increase the toxicity of phenytoin. Pharmacodynamic interactions are also possible. CONCLUSIONS: Information about the clinical consequences of the interactions between antiepileptics and antineoplastic agents is often based on cases or series of cases, but a growing body of evidence from pharmacokinetic studies shows that enzyme-inducing antiepileptics exert an important influence on the effectiveness of the antineoplastic agents. It is therefore recommendable to avoid them and replace them with non-enzyme-inducing antiepileptics, such as gabapentin, lamotrigine, levetiracetam, pregabalin, topiramate or zonisamide. When enzyme-inducing antiepileptics have to be used, it is likely that higher doses of antineoplastic agents or other inducible drugs will have to be utilised.

Anticonvulsants↗