Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0002874 (aplastic anemia)
 5,905 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the last few years a number of new anticonvulsants have been introduced into clinical practice mainly as add-on therapy in patients who do not become seizure-free while receiving established anticonvulsants. Up to now, no single drug has been shown to be more effective at controlling seizures of a particular type than another, so other factors such as mechanism of action, pharmacokinetics, dosage regimens or the spectrum of adverse drug reactions and interactions are used when making a choice between one agent and another. The mechanism of action of tiagabine and vigabatrin is very specific; both agents increase gamma-aminobutyric acid (GABA) levels through inhibition of reuptake and catabolism respectively. However, the mechanism of action of gabapentin is unknown and those of felbamate, lamotrigine and topiramate are not sufficiently clarified as yet, and may be multiple. Great advances have been made in improving the pharmacokinetic characteristics of these newer anticonvulsants. Gabapentin and vigabatrin exhibit relatively ideal pharmacokinetic properties as they are not bound to proteins, are excreted mostly unchanged in the urine and show linear pharmacokinetics. Lamotrigine possesses a highly variable elimination half-life depending on the co-medication. Tiagabine is highly protein bound and zonisamide shows nonlinear pharmacokinetics; both these drugs are extensively metabolised. Problematic drug interactions between newer anticonvulsants and other drugs in general occur rarely when these agents are given concomitantly. However, in common with most new drugs, there are very few data on the use of the newer anticonvulsants in women of childbearing age. Studies done so far on interactions with oral contraceptives used low anticonvulsant dosages for a very short time. The newer anticonvulsants elicit adverse reactions that, while not being unique, are particularly associated with that drug. For example, felbamate may cause aplastic anaemia and fulminant liver failure, lamotrigine is prone to cause skin rash, and oxcarbazepine may cause symptomatic hyponatraemia. Topiramate and zonisamide cause kidney stones, and vigabatrin may induce psychiatric syndromes. Although highly diverse in structure and activity, these newer drugs offer new possibilities for treating refractory epilepsy. However, since no single factor can dictate the choice of drug nor predict the success of treatment, prescribing of these rather expensive drugs has to depend upon careful consideration of the aims of treatment, the characteristics of the drug and the needs of the individual patient.
 ...
PMID:Newer anticonvulsant drugs: role of pharmacology, drug interactions and adverse reactions in drug choice. 935 59

In this review study, second-generation antiepileptic drugs (AEDs) (levetiracetam, gabapentin, topiramate, lamotrigine, zonisamide, oxcarbazepine, vigabatrin, pregabalin, rufinamide, tiagabine, lacosamide, and felbamate) and injectable AEDs (levetiracetam, lacosamide, fosphenytoin, lorazepam, and valproic acid) available in North America were compared with those available in Japan. Three second-generation AEDs (gabapentin, topiramate, and lamotrigine) were recently approved in Japan. Levetiracetam is currently under review for approval by the Japanese regulatory agency. An ideal AED would have a broad-spectrum activity to control multiple types of seizures, favorable safety profile, limited potential for drug-drug interaction, many bioequivalent formulations, long half life to allow infrequent administration, and antiepileptogenic effects that may provide a fundamental cure of epileptic patients by suppressing the development of epileptogenic network and neutralizing previously established epileptogenic foci in the brain. The second-generation AEDs have been developed to possess some of these ideal properties. All the second-generation AEDs are efficacious for the treatment of patients with partial seizures. In addition, levetiracetam, topiramate, lamotrigine, and zonisamide are effective for the treatment of patients with generalized tonic-clonic seizures, absences, myoclonic seizures, Lennox-Gastaut syndrome, and West syndrome; however, lamotrigine is not effective for the treatment of patients with myoclonic seizures. Rufinamide and felbamate are useful for the treatment of patients with Lennox-Gastaut syndrome; however owing to its serious adverse effects, including aplastic anemia and hepatic failure, felbamate is used as the last resort for the treatment of patients with intractable seizures. Vigabatrin is particularly effective for the treatment of patients with West syndrome; however, the patients need to be regularly monitored for the development of peripheral visual field defect. Gabapentin, oxcarbazepine, vigabatrin, and tiagabine are ineffective for the treatment of patients with absences and/or myoclonic seizures and may aggravate these conditions. Treatment with levetiracetam or topiramate (off-label use) is the new option for patients with refractory status epilepticus, which is characterized by downregulation of the inhibitory gamma-aminobutyric acid system, because these drugs act via different mechanisms and are rapidly titratable, especially intravenous levetiracetam. The pharmacokinetic profiles of levetiracetam, gabapentin, and pregabalin are favorable: these drugs exhibit minimal protein binding, do not undergo hepatic metabolism, are not involved in any clinically relevant drug interactions, and rarely lead to the development of serious adverse effects. In general, levetiracetam is probably the closest to being the ideal AED because of its broad-spectrum favorable pharmacokinetic profile and safety profile as well as because of the availability of its parenteral formulation. Among the injectable AEDs, fosphenytoin is a water-soluble prodrug and is used to treat patients with status epilepticus. Systemic and local side effects of this drug are fewer than those of phenytoin. Lorazepam, a benzodiazepine is used as the first-line AED for the treatment of patients with status epilepticus. The effects of this drug are more prolonged than those of diazepam. Intravenous administration of valproic acid is regarded as a new treatment option for patients with status epilepticus, because sedative and negative effects on the cardiorespiratory system of this drug are lesser than those of the traditional injectable AEDs. These novel medications will aid the improvement of the quality of life of epileptic patients through improved seizure control and reduced adverse effects.
 ...
PMID:[Antiepileptic drugs in North America]. 2045 99