Carbamazepine

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Carbamazepine
Carbamazepine.svg
Carbamazepine 3D.png
Systematic (IUPAC) name
5H-dibenzo[b,f]azepine-5-carboxamide
Clinical data
Trade names Tegretol
AHFS/Drugs.com monograph
MedlinePlus a682237
Licence data US Daily Med:link
Pregnancy
category
  • AU: D
  • US: D (Evidence of risk)
Legal status
Routes of
administration		 Oral
Pharmacokinetic data
Bioavailability ~100%[1]
Protein binding 70-80%[1]
Metabolism Hepatic—by CYP3A4, to active epoxide form (carbamazepine-10,11 epoxide)[1]
Biological half-life 36 hours (single dose), 16-24 hours (repeated dosing)[1]
Excretion Urine (72%), feces (28%)[1]
Identifiers
CAS Number 298-46-4 YesY Template:CAS
ATC code N03AF01 (WHO)
PubChem CID: 2554
IUPHAR/BPS 5339
DrugBank DB00564 YesY
ChemSpider 2457 YesY
UNII 33CM23913M YesY
KEGG D00252 YesY
ChEBI CHEBI:3387 YesY
ChEMBL CHEMBL108 YesY
Chemical data
Formula C15H12N2O
Molecular mass 236.269 g/mol
  • c1ccc2c(c1)C=Cc3ccccc3N2C(=O)N
  • InChI=1S/C15H12N2O/c16-15(18)17-13-7-3-1-5-11(13)9-10-12-6-2-4-8-14(12)17/h1-10H,(H2,16,18) YesY
  • Key:FFGPTBGBLSHEPO-UHFFFAOYSA-N YesY
  (verify)

Carbamazepine (CBZ), sold under the tradename Tegretol among others, is a medication used primarily in the treatment of epilepsy and neuropathic pain.[2] For seizures it works as well as phenytoin and valproate.[3][4] It is not effective for absence seizures or myoclonic seizures. It may be used in schizophrenia along with other medications and as a second line agent in bipolar disorder.[2] It is taken two to four times per day.[2] A controlled release formulation is available for which there is tentative evidence showing less side effects.[5]

Common side effects include nausea and drowsiness. Serious side effects may include skin rashes, decreased bone marrow function, suicidal thoughts, or confusion. It should not be used in those with a history of bone marrow problems. Use during pregnancy may cause harm to the baby; however stopping it in pregnant women with seizures is not recommended. Its use during breastfeeding is not recommended. Care should be taken in those with either kidney or liver problems.[2]

Carbamazepine was discovered in 1953 by Swiss chemist Walter Schindler.[6] It was first marketed in 1962.[7] It is available as a generic medication and is not very expensive.[8] It is on the WHO Model List of Essential Medicines, the most important medications needed in a basic health system.[9] The wholesale cost is between 0.01 and 0.07 USD per dose as of 2014.[10]

Medical uses

Tegretol 200-mg CR (made in NZ)

Carbamazepine is typically used for the treatment of seizure disorders and neuropathic pain.[2] It is used off-label as a second-line treatment for bipolar disorder and in combination with an antipsychotic in some cases of schizophrenia when treatment with a conventional antipsychotic alone has failed.[2][11]

In the United States, the FDA-approved medical uses are epilepsy (including partial seizures, generalized tonic-clonic seizures and mixed seizures), trigeminal neuralgia, and manic and mixed episodes of bipolar I disorder.[12]

It is unclear if there is a significant difference in effectiveness between controlled release and immediate release formulations in epilepsy.[13] Controlled release forms might, however, have lower risks of side effects.[13]

Adverse effects

In the US, the label for carbamazepine contains warnings concerning:

Common adverse effects may include drowsiness, dizziness, headaches and migraines, motor coordination impairment, nausea, vomiting, and/or constipation. Alcohol use while taking carbamazepine may lead to enhanced depression of the central nervous system.[1] Less common side effects may include increased risk of seizures in people with mixed seizure disorders,[15] abnormal heart rhythms, blurry or double vision.[1] Also, rare case reports of an auditory side effect have been made, whereby patients perceive sounds about a semitone lower than previously; this unusual side effect is usually not noticed by most people, and disappears after the person stops taking carbamazepine.[16]

Interactions

Carbamazepine has a potential for drug interactions; caution should be used in combining other medicines with it, including other antiepileptics and mood stabilizers.[12] Lower levels of carbamazepine are seen when administrated with phenobarbital, phenytoin (Dilantin), or primidone (Mysoline), which can result in breakthrough seizure activity. Carbamazepine, as a CYP450 inducer, may increase clearance of many drugs, decreasing their concentration in the blood to subtherapeutic levels and reducing their desired effects.[17] Drugs that are more rapidly metabolized with carbamazepine include warfarin, lamotrigine, phenytoin, theophylline, and valproic acid.[12] Drugs that decrease the metabolism of carbamazepine or otherwise increase its levels include erythromycin,[18] cimetidine, propoxyphene, and calcium channel blockers.[12] Carbamazepine also increases the metabolism of the hormones in birth control pills and can reduce their effectiveness, potentially leading to unexpected pregnancies.[12] As a drug that induces cytochrome P450 enzymes, it accelerates elimination of many benzodiazepines and decreases their action.[19]

Valproic acid and valnoctamide both inhibit microsomal epoxide hydrolase (MEH), the enzyme responsible for the breakdown of carbamazepine-10,11 epoxide into inactive metabolites.[20] By inhibiting MEH, valproic acid and valnoctamide cause a build-up of the active metabolite, prolonging the effects of carbamazepine and delaying its excretion.

Grapefruit juice raises the bioavailability of carbamazepine by inhibiting CYP3A4 enzymes in the gut wall and in the liver.[1]

Pharmacogenetics

Dangerous and potentially fatal skin reactions, including Stevens–Johnson syndrome and toxic epidermal necrolysis, caused by carbamazepine therapy are significantly more common in patients with a particular human leukocyte antigen allele, HLA-B*1502.[21] Odds ratios for the development of Stevens-Johnson syndrome or toxic epidermal necrolysis in patients who carry the allele can be in the double, triple or even quadruple digits, depending on the population studied.[22][23] HLA-B*1502 occurs almost exclusively in patients with ancestry across broad areas of Asia, but has a very low or absent frequency in European, Japanese, Korean and African populations.[21][24] However, the HLA-A*31:01 allele has been shown to be a strong predictor of both mild and severe adverse reactions to carbamazepine among Japanese and Europeans.[23]

Pharmacokinetics

Carbamazepine is relatively slowly but well absorbed after oral administration. Its plasma half-life is about 30 hours when it is given as single dose, but it is a strong inducer of hepatic enzymes and the plasma half-life shortens to about 15 hours when it is given repeatedly.[medical citation needed]

Mechanism of action

The mechanism of action of carbamazepine and its derivatives is relatively well understood. Carbamazepine stabilizes the inactivated state of voltage-gated sodium channels, making fewer of these channels available to subsequently open. This leaves the affected cells less excitable until the drug dissociates.[citation needed] Carbamazepine is also a GABA receptor agonist, as it has also been shown to potentiate GABA receptors made up of alpha1, beta2, and gamma2 subunits.[25] This mechanism may contribute to its efficacy in neuropathic pain and manic-depressive illness. Laboratory research has further demonstrated that carbamazepine is a serotonin releasing agent and possibly even a serotonin reuptake inhibitor. [26] [27] [28]

History

Carbamazepine was discovered by chemist Walter Schindler at J.R. Geigy AG (now part of Novartis) in Basel, Switzerland, in 1953.[29][30] It was first marketed as a drug to treat epilepsy in Switzerland in 1963 under the brand name "Tegretol"; its use for trigeminal neuralgia (formerly known as tic douloureux) was introduced at the same time.[29] It has been used as an anticonvulsant and antiepileptic in the UK since 1965, and has been approved in the US since 1968.[2]

In 1971, Drs. Takezaki and Hanaoka first used carbamazepine to control mania in patients refractory to antipsychotics (lithium was not available in Japan at that time). Dr. Okuma, working independently, did the same thing with success. As they were also epileptologists, they had some familiarity with the antiaggression effects of this drug. Carbamazepine was studied for bipolar disorder throughout the 1970s.[31]

Environmental fate

<templatestyles src="Module:Hatnote/styles.css"></templatestyles>

Main article: Environmental impact of pharmaceuticals and personal care products

Carbamazepine has been detected in wastewater effluent.[32]:224 Field and laboratory studies have been conducted to understand the accumulation of carbamazepine in food plants grown in soil treated with sludge, which vary with respect to the concentrations of carbamazepine present in sludge and in the concentrations of sludge in the soil; taking into account only studies that used concentrations normally found, a 2014 review found that "the accumulation of carbamazepine into plants grown in soil amended with biosolids poses a de minimis risk to human health according to the approach."[32]:227

Brand names

Carbamazepine is available worldwide under many brand names.[33]

See also

References

  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ 12.0 12.1 12.2 12.3 12.4 Lua error in package.lua at line 80: module 'strict' not found. Retrieved on May 3, 2009.
  13. ↑ 13.0 13.1 Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  18. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  19. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  20. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  21. ↑ 21.0 21.1 Lua error in package.lua at line 80: module 'strict' not found.
  22. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  23. ↑ 23.0 23.1 Lua error in package.lua at line 80: module 'strict' not found.
  24. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  25. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  26. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  27. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  28. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  29. ↑ 29.0 29.1 D.F. Scott. "Carbamazepine". Chapter 8 in The History of Epileptic Therapy: An Account of How Medication was Developed. History of Medicine Series. CRC Press, 1993 ISBN 9781850703914
  30. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  31. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  32. ↑ 32.0 32.1 Prosser RS, Sibley PK2. Human health risk assessment of pharmaceuticals and personal care products in plant tissue due to biosolids and manure amendments, and wastewater irrigation. Environ Int. 2014 Dec 5;75C:223-233. doi: 10.1016/j.envint.2014.11.020. PMID 25486094
  33. ↑ drugs.com drugs.com international listings for carbamazepine Page accessed June 3, 2015

External links


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