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Anticonvulsant
Anticonvulsants (also commonly known as antiepileptic drugs or as antiseizure drugs) are a diverse group of pharmacological agents used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of bipolar disorder and borderline personality disorder,〔American Psychiatric Association, and American Psychiatric Association. Work Group on Borderline Personality Disorder. Practice guideline for the treatment of patients with borderline personality disorder. American Psychiatric Pub, 2001.〕 since many seem to act as mood stabilizers, and for the treatment of neuropathic pain. Anticonvulsants suppress the rapid and excessive firing of neurons during seizures. Anticonvulsants also prevent the spread of the seizure within the brain. Some investigators have observed that anticonvulsants themselves may cause reduced IQ in children. However these adverse effects must be balanced against the significant risk epileptic seizures pose to children and the distinct possibility of death and devastating neurological sequelae secondary to seizures. Anticonvulsants are more accurately called antiepileptic drugs (abbreviated "AEDs"), and are often referred to as antiseizure drugs because they provide symptomatic treatment only and have not been demonstrated to alter the course of epilepsy.
Conventional antiepileptic drugs may block sodium channels or enhance γ-aminobutyric acid (GABA) function. Several antiepileptic drugs have multiple or uncertain mechanisms of action.〔https://www.neurology.wisc.edu/publications/2010%20pubs/stafstrom-4.pdf〕 Next to the voltage-gated sodium channels and components of the GABA system, their targets include GABAA receptors, the GAT-1 GABA transporter, and GABA transaminase. Additional targets include voltage-gated calcium channels, SV2A, and α2δ. By blocking sodium or calcium channels, antiepileptic drugs reduce the release of excitatory glutamate, whose release is considered to be elevated in epilepsy, but also that of GABA. This is probably a side effect or even the actual mechanism of action for some antiepileptic drugs, since GABA can itself, directly or indirectly, act proconvulsively.〔 Another potential target of antiepileptic drugs is the peroxisome proliferator-activated receptor alpha. The drug class was the 5th-best-selling in the US in 2007.〔http://www.joacp.org/index.php?option=com_content&view=article&id=188&catid=1 "According to the Washington Post who quoted research from IMS Health, AEDs were the fifth best selling class of drugs in the US in 2007, with sales topping 10 billion dollars. "〕
Some anticonvulsants have shown antiepileptogenic effects in animal models of epilepsy. That is, they either prevent the development of epilepsy or can halt or reverse the progression of epilepsy. However, no drug has been shown in human trials to prevent epileptogenesis (the development of epilepsy in an individual at risk, such as after a head injury).
==Approval==
The usual method of achieving approval for a drug is to show it is effective when compared against placebo, or that it is more effective than an existing drug. In monotherapy (where only one drug is taken) it is considered unethical by most to conduct a trial with placebo on a new drug of uncertain efficacy. This is because untreated epilepsy leaves the patient at significant risk of death. Therefore, almost all new epilepsy drugs are initially approved only as adjunctive (add-on) therapies. Patients whose epilepsy is currently uncontrolled by their medication (i.e., it is refractory to treatment) are selected to see if supplementing the medication with the new drug leads to an improvement in seizure control. Any reduction in the frequency of seizures is compared against a placebo.〔 The lack of superiority over existing treatment, combined with lacking placebo-controlled trials, means that few modern drugs have earned FDA approval as initial monotherapy. In contrast, Europe only requires equivalence to existing treatments, and has approved many more. Despite their lack of FDA approval, the American Academy of Neurology and the American Epilepsy Society still recommend a number of these new drugs as initial monotherapy.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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