World Library  
Flag as Inappropriate
Email this Article

Antiepileptic

 

Antiepileptic

The anticonvulsants (also commonly known as antiepileptic drugs) are a diverse group of pharmaceuticals used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of bipolar disorder, since many seem to act as mood stabilizers, and for the treatment of neuropathic pain. The goal of an anticonvulsant is to suppress the rapid and excessive firing of neurons that start a seizure. Failing this, an effective anticonvulsant would prevent the spread of the seizure within the brain and offer protection against possible excitotoxic effects, that may result in brain damage. Some studies have cited that anticonvulsants themselves are linked to lowered IQ in children.[1] However these adverse effects must be balanced against the significant risk epileptiform seizures pose to children and the distinct possibility of death and devastating neurological sequela secondary to seizures. Anticonvulsants are more accurately called antiepileptic drugs (abbreviated "AEDs"), and are sometimes referred to as antiseizure drugs. While the term 'anticonvulsant' is a fair description of AEDs, the use of this term tends to lead to confusion between epilepsy and non-epileptic convulsions. Convulsive non-epileptic seizures are quite common, and these types of seizures do not respond to antiepileptic drugs. In epilepsy, an area of the cortex is typically hyper-irritable. This condition can often be confirmed by completing a diagnostic EEG. Antiepileptic drugs function to help reduce this area of irritability and thus prevent epileptiform seizures.

Conventional antiepileptic drugs block sodium channels or enhance g-aminobutyric acid function. Several antiepileptic drugs have multiple or uncertain mechanisms of action.[2] 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.[3] Additional targets include voltage-gated calcium channels, SV2A, and α2δ.[4][5] The drug class was the US's 5th-best-selling in 2007.[6]

Some anticonvulsants have shown antiepileptogenic effects in animal models of epilepsy. That is, they either prevent the expected development of epilepsy or can halt or reverse the progression of epilepsy. However, no drug has been shown to prevent epileptogenesis (the development of epilepsy after an injury such as a head injury) in human trials.[7]

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.[7] 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.[7]

Drugs

In the following list, the dates in parentheses are the earliest approved use of the drug.

Aldehydes

Main article: Aldehyde
  • Paraldehyde (1882). One of the earliest anticonvulsants. Still used to treat status epilepticus, particularly where there are no resuscitation facilities.

Aromatic allylic alcohols

Barbiturates

Main article: Barbiturate

Barbiturates are drugs that act as central nervous system (CNS) depressants, and by virtue of this they produce a wide spectrum of effects, from mild sedation to anesthesia. The following are classified as anticonvulsants:

Phenobarbital was the main anticonvulsant from 1912 till the development of phenytoin in 1938. Today, phenobarbital is rarely used to treat epilepsy in new patients since there are other effective drugs that are less sedating. Phenobarbital sodium injection can be used to stop acute convulsions or status epilepticus, but a benzodiazepine such as lorazepam, diazepam or midazolam is usually tried first. Other barbiturates only have an anticonvulsant effect at anaesthetic doses.

Benzodiazepines

Main article: Benzodiazepine

The benzodiazepines are a class of drugs with hypnotic, anxiolytic, anticonvulsive, amnestic and muscle relaxant properties. Benzodiazepines act as a central nervous system depressant. The relative strength of each of these properties in any given benzodiazepine varies greatly and influences the indications for which it is prescribed. Long-term use can be problematic due to the development of tolerance to the anticonvulsant effects and dependency.[10][11][12][13] Of the many drugs in this class, only a few are used to treat epilepsy:

The following benzodiazepines are used to treat status epilepticus:

  • Diazepam (1963). Can be given rectally by trained care-givers.
  • Midazolam (N/A). Increasingly being used as an alternative to diazepam. This water-soluble drug is squirted into the side of the mouth but not swallowed. It is rapidly absorbed by the buccal mucosa.
  • Lorazepam (1972). Given by injection in hospital.

Nitrazepam, temazepam, and especially nimetazepam are powerful anticonvulsant agents, however their use is rare due to an increased incidence of side effects and strong sedative and motor-impairing properties.

Bromides

Main article: Bromide
  • Potassium bromide (1857). The earliest effective treatment for epilepsy. There would not be a better drug until phenobarbital in 1912. It is still used as an anticonvulsant for dogs and cats.

Carbamates

Main article: Carbamate
  • Felbamate (1993). This effective anticonvulsant has had its usage severely restricted due to rare but life-threatening side effects.[14][15][16]

Carboxamides

Main article: Carboxamide

The following are carboxamides:

  • Carbamazepine (1963). A popular anticonvulsant that is available in generic formulations.
  • Oxcarbazepine (1990). A derivative of carbamazepine that has similar efficacy but is better tolerated and is also available generically.
  • Eslicarbazepine acetate (2009)

Fatty acids

Main article: Fatty acid

The following are fatty-acids:

Vigabatrin and progabide are also analogs of GABA.

Fructose derivatives

Main article: Fructose

GABA analogs

Hydantoins

Main article: Hydantoin

The following are hydantoins:

Oxazolidinediones

Main article: Oxazolidinedione

The following are oxazolidinediones:

Propionates

Main article: Propionate

Pyrimidinediones

Main article: Pyrimidinedione

Pyrrolidines

Main article: Pyrrolidine

Succinimides

Main article: Succinimide

The following are succinimides:

Sulfonamides

Triazines

Main article: Triazine

Ureas

Main article: Urea

Valproylamides (amide derivatives of valproate)

Main article: Amide

Non-medical anticonvulsants

This article is about anticonvulsant drugs. For non-medical "anticonvulsants", see Epilepsy#Other treatment.

Sometimes, ketogenic diet or vagus nerve stimulation are described as "anticonvulsant" therapies as well.

Treatment guidelines

According to guidelines by the AAN and AES,[17] mainly based on a major article review in 2004,[18] patients with newly diagnosed epilepsy who require treatment can be initiated on standard anticonvulsants such as carbamazepine, phenytoin, valproic acid/valproate semisodium, phenobarbital, or on the newer anticonvulsants gabapentin, lamotrigine, oxcarbazepine or topiramate. The choice of anticonvulsants depends on individual patient characteristics.[17] Both newer and older drugs are generally equally effective in new onset epilepsy.[17] The newer drugs tend to have fewer side effects.[17] For newly diagnosed partial or mixed seizures, there is evidence for using gabapentin, lamotrigine, oxcarbazepine or topiramate as monotherapy.[17] Lamotrigine can be included in the options for children with newly diagnosed absence seizures.[17]

History

The first anticonvulsant was bromide, suggested in 1857 by Charles Locock who used it to treat women with "hysterical epilepsy" (probably catamenial epilepsy). Bromides are effective against epilepsy, and also cause impotence, which is not related to its anti-epileptic effects. Bromide also suffered from the way it affected behaviour, introducing the idea of the 'epileptic personality' which was actually a result of medication. Phenobarbital was first used in 1912 for both its sedative and antiepileptic properties. By the 1930s, the development of animal models in epilepsy research led to the development of phenytoin by Tracy Putnam and H. Houston Merritt, which had the distinct advantage of treating epileptic seizures with less sedation.[19] By the 1970s, an National Institutes of Health initiative, the Anticonvulsant Screening Program, headed by J. Kiffin Penry, served as a mechanism for drawing the interest and abilities of pharmaceutical companies in the development of new anticonvulsant medications.

Marketing approval history

The following table lists anticonvulsant drugs together with the date their marketing was approved in the US, UK and France. Data for the UK and France are incomplete. In recent years, the European Medicines Agency has approved drugs throughout the European Union. Some of the drugs are no longer marketed.

Drug Brand US UK France
acetazolamide Diamox 1953-07-2727 July 1953[20] 1988[21]
carbamazepine Tegretol 1974-07-1515 July 1974[22][23] 1965[21] 1963[24]
clobazam Frisium 1979[21]
clonazepam Klonopin/Rivotril 1975-06-044 June 1975[25] 1974[21]
diazepam Valium 1963-11-1515 November 1963[26]
divalproex sodium Depakote 1983-03-1010 March 1983[27]
eslicarbazepine Data needed
ethosuximide Zarontin 1960-11-022 November 1960[28] 1955[21] 1962[24]
ethotoin Peganone 1957-04-2222 April 1957[29]
felbamate Felbatol 1993-07-2929 July 1993[30]
fosphenytoin Cerebyx 1996-08-055 August 1996[31]
gabapentin Neurontin 1993-12-3030 December 1993[32] 1993-05May 1993[21][24] 1994-10October 1994[24]
lamotrigine Lamictal 1994-12-2727 December 1994[33] 1991-10October 1991[21][24] 1995-05May 1995[24]
lacosamide Vimpat 2008-10-2828 October 2008[34]
levetiracetam Keppra 1999-11-3030 November 1999[35] 2000-09-2929 September 2000[21][36] 2000-09-2929 September 2000[36]
mephenytoin Mesantoin 1946-10-2323 October 1946[37]
metharbital Gemonil 1952[38][39]
methsuximide Celontin 1957-02-088 February 1957[40]
methazolamide Neptazane 1959-01-2626 January 1959[41]
oxcarbazepine Trileptal 2000-01-1414 January 2000[42] 2000[21]
phenobarbital 1912[21] 1920[24]
phenytoin Dilantin/Epanutin 1938[24][43] 1938[21] 1941[24]
phensuximide Milontin 1953[44][45]
pregabalin Lyrica 2004-12-3030 December 2004[46] 2004-07-066 July 2004[21][47] 2004-07-066 July 2004[47]
primidone Mysoline 1954-03-088 March 1954[48] 1952[21] 1953[24]
sodium valproate Epilim 1977-12December 1977[24] 1967-06June 1967[24]
stiripentol Diacomit 2001-12-055 December 2001[49] 2001-12-055 December 2001[49]
tiagabine Gabitril 1997-09-3030 September 1997[50][51] 1998[21] 1997-11November 1997[24]
topiramate Topamax 1996-12-2424 December 1996[52] 1995[21]
trimethadione Tridione 1946-01-2525 January 1946[53]
valproic acid Depakene/Convulex 1978-02-2828 February 1978[54] 1993[21]
vigabatrin Sabril 2009-08-2121 August 2009[55] 1989[21]
zonisamide Zonegran 2000-03-2727 March 2000[56] 2005-03-1010 March 2005[21][57] 2005-03-1010 March 2005[57]

Use in pregnancy

During pregnancy, the metabolism of several anticonvulsants is affected. There may be an increase in the clearance and resultant decrease in the blood concentration of lamotrigine, phenytoin, and to a lesser extent carbamazepine, and possibly decreases the level of levetiracetam and the active oxcarbazepine metabolite, the monohydroxy derivative.[58] Therefore, these drugs should be monitored during use in pregnancy.[58] Taking valproic acid or divalproex sodium during pregnancy should be cautioned against, as this class of medications has been linked to birth defects (teratogenic).

There is inadequate evidence to determine if newborns of women with epilepsy taking anticonvulsants have a substantially increased risk of hemorrhagic disease of the newborn.[58]

Regarding breastfeeding, some anticonvulsants probably pass into breast milk in clinically significant amounts, including primidone and levetiracetam.[58] On the other hand, valproate, phenobarbital, phenytoin, and carbamazepine probably are not transferred into breast milk in clinically important amounts.[58]

In animal models, several anticonvulsant drugs have been demonstrated to induce neuronal apoptosis in the developing brain.[59][60][61][62][63]

See also

References

  • Drug Reference for FDA Approved Epilepsy Drugs
  • Epilepsy Action: UK Anti-Epileptic Drugs List

External links

  • eMedicine: Antiepileptic Drugs: an overview
  • NINDS: Anticonvulsant Screening Program
  • Use of Anticonvulsants in Pharmacotherapy of Bronchial Asthma
  • MDNG: Anticonvulsants and Bone Health
  • Miami Children's Brain Institute - Anticonvulsants
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.