Anticonvulsant

From Wikipedia, the free encyclopedia

The anticonvulsants, also called antiepileptic drugs (abbreviated "AEDs"), belong to a diverse group of pharmaceuticals used in prevention of the occurrence of epileptic seizures. Anticonvulsants are also increasingly finding ways into the treatment of bipolar disorder, since many seem to act as mood stabilizers. The goal of an anticonvulsant is to suppress the rapid and excessive firing of neurons that start a seizure. Failing this, a good anticonvulsant would prevent the spread of the seizure within the brain and offer protection against possible excitotoxic effects that may result in brain damage. However, anticonvulsants themselves have been linked to lowered IQ.[1]

The major molecular targets of marketed anticonvulsant drugs are voltage-gated sodium channels; components of the GABA system, including GABAA receptors, the GAT-1 GABA transporter, and GABA transaminase; and voltage-gated calcium channels.[2]

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 shown this effect in human trials.[3]

Contents

[edit] 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.[3]

Once there is confidence that a drug is likely to be effective in monotherapy, trials are conducted where the drug is compared to an existing standard. For partial-onset seizures, this is typically carbamazepine. Despite the launch of over ten drugs since 1990, no new drug has been shown to be more effective than the older set, which includes carbamazepine, valproate and phenytoin. The lack of superiority over existing treatment, combined with the lack of 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.[3]

[edit] Drugs

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

[edit] Aldehydes

Main article: Aldehydes

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

[edit] Aromatic allylic alcohols

  • Stiripentol (2001 - limited availability). Indicated for the treatment of severe myoclonic epilepsy in infancy (SMEI).

[edit] Barbiturates

Main article: Barbiturates

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.

[edit] Benzodiazepines

Main article: Benzodiazepines

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 and dependency. Of the many drugs in this class, only a few are used to treat epilepsy:

  • Clobazam (1979). Notably used on a short-term basis around menstruation in women with catamenial epilepsy.
  • Clonazepam (1974).
  • Clorazepate (1972).

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.

[edit] Bromides

Main article: Bromides

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

[edit] Carbamates

Main article: Carbamates

  • Felbamate (1993). This effective anticonvulsant has had its usage severely restricted due to rare but life-threatening side effects.

[edit] Carboxamides

Main article: Carboxamides

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.

[edit] Fatty acids

Main article: Fatty acids

The following are fatty-acids:

Vigabatrin and progabide are also analogs of GABA.

[edit] Fructose derivatives

Main article: Fructose

[edit] Gaba analogs

[edit] Hydantoins

Main article: Hydantoins

The following are hydantoins:

[edit] Oxazolidinediones

Main article: Oxazolidinediones

The following are oxazolidinediones:

[edit] Propionates

Main article: Propionates

[edit] Pyrimidinediones

Main article: Pyrimidinediones

[edit] Pyrrolidines

Main article: Pyrrolidines

[edit] Succinimides

Main article: Succinimides

The following are succinimides:

[edit] Sulfonamides

Main article: Sulfonamides

[edit] Triazines

Main article: Triazines

[edit] Ureas

Main article: Ureas

[edit] Valproylamides (amide derivatives of valproate)

Main article: Amides

[edit] Diet

The ketogenic diet is a strict medically supervised diet that has an anticonvulsant effect. It is typically used in children with refractory epilepsy.

[edit] Devices

The vagus nerve stimulator (VNS) is a device that sends electric impulses to the left vagus nerve in the neck via a lead implanted under the skin. It was FDA approved in 1997 as an adjunctive therapy for partial-onset epilepsy.

[edit] 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 is 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 1953-07-271953-07-27[4] 1988[5]
carbamazepine Tegretol 1974-07-151974-07-15[6][7] 1965[5] 1963[8]
clobazam Frisium 1979[5]
clonazepam Klonopin/Rivotril 1975-06-041975-06-04[9] 1974[5]
diazepam Valium 1963-11-151963-11-15[10]
divalproex sodium Depakote 1983-03-101983-03-10[11]
ethosuximide Zarontin 1960-11-021960-11-02[12] 1955[5] 1962[8]
ethotoin Peganone 1957-04-221957-04-22[13]
felbamate Felbatol 1993-07-291993-07-29[14]
fosphenytoin Cerebyx 1996-08-051996-08-05[15]
gabapentin Neurontin 1993-12-301993-12-30[16] 1993-05May 1993[5][8] 1994-10October 1994[8]
lamotrigine Lamictal 1994-12-271994-12-27[17] 1991-10October 1991[5][8] 1995-05May 1995[8]
levetiracetam Keppra 1999-11-301999-11-30[18] 2000-09-292000-09-29[5][19] 2000-09-292000-09-29[19]
mephenytoin Mesantoin 1946-10-231946-10-23[20]
metharbital Gemonil 1952[21][22]
methsuximide Celontin 1957-02-081957-02-08[23]
methazolamide Neptazane 1959-01-261959-01-26[24]
oxcarbazepine Trileptal 2000-01-142000-01-14[25] 2000[5]
phenobarbital 1912[5] 1920[8]
phenytoin Dilantin/Epanutin 1938[26][8] 1938[5] 1941[8]
phensuximide Milontin 1953[27][28]
pregabalin Lyrica 2004-12-302004-12-30[29] 2004-07-062004-07-06[5][30] 2004-07-062004-07-06[30]
primidone Mysoline 1954-03-081954-03-08[31] 1952[5] 1953[8]
sodium valproate Epilim 1977-12December 1977[8] 1967-06June 1967[8]
stiripentol Diacomit 2001-12-052001-12-05[32] 2001-12-052001-12-05[32]
tiagabine Gabitril 1997-09-301997-09-30[33] 1998[5] 1997-11November 1997[8]
topiramate Topamax 1996-12-241996-12-24[34] 1995[5]
trimethadione Tridione 1946-01-251946-01-25[35]
valproic acid Depakene/Convulex 1978-02-281978-02-28[36] 1993[5]
vigabatrin Sabril 1989[5]
zonisamide Zonegran 2000-03-272000-03-27[37] 2005-03-102005-03-10[5][38] 2005-03-102005-03-10[38]

[edit] See also

[edit] References

  1. ^ Loring, David W (2005-09-01). "Cognitive Side Effects of Antiepileptic Drugs in Children". Psychiatric Times XXII (10). 
  2. ^ Rogawski MA, Löscher W. The neurobiology of antiepileptic drugs. Nat Rev Neurosci. 2004 Jul;5(7):553-564. PMID 15208697
  3. ^ a b c Abou-Khalil BW (2007). "Comparative monotherapy trials and the clinical treatment of epilepsy". Epilepsy currents / American Epilepsy Society 7 (5): 127–9. doi:10.1111/j.1535-7511.2007.00198.x. PMID 17998971. 
  4. ^ NDA 008943
  5. ^ a b c d e f g h i j k l m n o p q r Epilepsy Action: Druglist. Retrieved on 2007-11-01.
  6. ^ NDA 016608 (Initial approval on 1968-03-11 was for trigeminal neuralgia.)
  7. ^ Schain, Richard J. (March 1978). "Pediatrics—Epitomes of Progress: Carbamazepine (Tegretol) in the Treatment of Epilepsy". Western Journal of Medicine 128 (3): 231–232. 
  8. ^ a b c d e f g h i j k l m Loiseau, Pierre Jean-Marie (June 1999). "Clinical Experience with New Antiepileptic Drugs: Antiepileptic Drugs in Europe" (PDF). Epilepsia 40 (Suppl 6): S3–8. doi:10.1111/j.1528-1157.1999.tb00925.x. PMID 10530675. 
  9. ^ NDA 017533
  10. ^ NDA 013263
  11. ^ NDA 018723
  12. ^ NDA 012380
  13. ^ NDA 010841
  14. ^ NDA 020189
  15. ^ NDA 020450
  16. ^ NDA 020235
  17. ^ NDA 020241
  18. ^ NDA 021035
  19. ^ a b EPAR: Keppra. Retrieved on 2007-11-01.
  20. ^ NDA 006008
  21. ^ NDA 008322
  22. ^ Dodson, W. Edwin; Giuliano Avanzini; Shorvon, Simon D.; Fish, David R.; Emilio Perucca (2004). The treatment of epilepsy. Oxford: Blackwell Science, xxviii. ISBN 0-632-06046-8. 
  23. ^ NDA 010596
  24. ^ NDA 011721
  25. ^ NDA 021014
  26. ^ NDA 008762 (Marketed in 1938, approved 1953)
  27. ^ NDA 008855
  28. ^ Kutt, Henn; Resor, Stanley R. (1992). The Medical treatment of epilepsy. New York: Dekker, 385. ISBN 0-8247-8549-5.  (first usage)
  29. ^ NDA 021446
  30. ^ a b EPAR: Lyrica Retrieved on 2007-11-01.
  31. ^ NDA 009170
  32. ^ a b EPAR: Diacomit. Orphan designation: 2001-12-05, full authorisation: 2007-01-04 Retrieved on 2007-11-01.
  33. ^ NDA 020646
  34. ^ NDA 020505
  35. ^ NDA 005856
  36. ^ NDA 018081
  37. ^ NDA 020789
  38. ^ a b EPAR: Zonegran. Retrieved on 2007-11-01

[edit] External links

v • d • e
Anticonvulsants (N03)
Barbiturates
Hydantoins
Oxazolidinediones
Succinimides
Benzodiazepines
Carboxamides
Fatty acid derivatives
Carboxylic acids
Others
v • d • e
Major drug groups
Gastrointestinal tract (A)
Blood and blood forming organs (B)
Cardiovascular system (C)
Skin (D)
Reproductive system (G)
Endocrine system (H)
Infections and infestations (J, P)
Malignant and immune disease (L)
Muscles, bones, and joints (M)
Brain and nervous system (N)
Respiratory system (R)