Clinical data | |
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Trade names | Tegretol, others |
Other names | CBZ |
AHFS/Drugs.com | Monograph |
MedlinePlus | a682237 |
License data | |
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Routes of administration | By mouth |
Drug class | Anticonvulsant [1] |
ATC code | |
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Pharmacokinetic data | |
Bioavailability | ~100% [5] |
Protein binding | 70–80% [5] |
Metabolism | Liver (CYP3A4) [5] |
Metabolites | Active epoxide form (carbamazepine-10,11 epoxide) [5] |
Elimination half-life | 36 hours (single dose), 16–24 hours (repeated dosing) [5] |
Excretion | Urine (72%), feces (28%) [5] |
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ChEBI | |
ChEMBL | |
CompTox Dashboard (EPA) | |
ECHA InfoCard | 100.005.512 |
Chemical and physical data | |
Formula | C15H12N2O |
Molar mass | 236.274 g·mol−1 |
3D model (JSmol) | |
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Carbamazepine, sold under the brand name Tegretol among others, is an anticonvulsant medication used in the treatment of epilepsy and neuropathic pain. [4] [1] It is used as an adjunctive treatment in schizophrenia along with other medications and as a second-line agent in bipolar disorder. [6] [1] Carbamazepine appears to work as well as phenytoin and valproate for focal and generalized seizures. [7] It is not effective for absence or myoclonic seizures. [1]
Carbamazepine was discovered in 1953 by Swiss chemist Walter Schindler. [8] [9] It was first marketed in 1962. [10] It is available as a generic medication. [11] It is on the World Health Organization's List of Essential Medicines. [12] In 2020, it was the 185th most commonly prescribed medication in the United States, with more than 2 million prescriptions. [13] [14]
Photoswitchable analogues of carbamazepine have been developed to control its pharmacological activity locally and on demand using light, with the purpose to reduce adverse systemic effects. [15] One of these compounds (carbadiazocine, based on a bridged azobenzene) has been shown to produce analgesia with noninvasive illumination in a rat model of neuropathic pain.
Carbamazepine is typically used for the treatment of seizure disorders and neuropathic pain. [1] 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. [1] [16] However, evidence does not support its usage for schizophrenia. [17] It is not effective for absence seizures or myoclonic seizures. [1] Although carbamazepine may have a similar effectiveness (as measured by people continuing to use a medication) and efficacy (as measured by the medicine reducing seizure recurrence and improving remission) when compared to phenytoin and valproate, choice of medication should be evaluated on an individual basis as further research is needed to determine which medication is most helpful for people with newly-onset seizures. [7]
In the United States, carbamazepine is indicated for the treatment of epilepsy (including partial seizures, generalized tonic-clonic seizures and mixed seizures), and trigeminal neuralgia. [4] [18] Carbamazepine is the only medication that is approved by the Food and Drug Administration for the treatment of trigeminal neuralgia. [19]
As of 2014, a controlled release formulation was available for which there is tentative evidence showing fewer side effects and unclear evidence with regard to whether there is a difference in efficacy. [20]
It has also been shown to improve symptoms of "typewriter tinnitus", a type of tinnitus caused by the neurovascular compression of the cochleovestibular nerve. [21]
In the US, the label for carbamazepine contains warnings concerning: [4]
Common adverse effects may include drowsiness, dizziness, headaches and migraines, ataxia, nausea, vomiting, and/or constipation. Alcohol use while taking carbamazepine may lead to enhanced depression of the central nervous system. [5] Less common side effects may include increased risk of seizures in people with mixed seizure disorders, [25] abnormal heart rhythms, blurry or double vision. [5] 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. [26]
Serious skin reactions such as Stevens–Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN) due to carbamazepine therapy are more common in people with a particular human leukocyte antigen gene-variant (allele), HLA-B*1502. [5] Odds ratios for the development of SJS or TEN in people who carry the allele can be in the double, triple or even quadruple digits, depending on the population studied. [27] [28] HLA-B*1502 occurs almost exclusively in people with ancestry across broad areas of Asia, but has a very low or absent frequency in European, Japanese, Korean and African populations. [5] [29] However, the HLA-A*31:01 allele has been shown to be a strong predictor of both mild and severe adverse reactions, such as the DRESS form of severe cutaneous reactions, to carbamazepine among Japanese, Chinese, Korean, and Europeans. [28] [30] It is suggested that carbamazepine acts as a potent antigen that binds to the antigen-presenting area of HLA-B*1502 alike, triggering an everlasting activation signal on immature CD8-T cells, thus resulting in widespread cytotoxic reactions like SJS/TEN. [31]
Carbamazepine has a potential for drug interactions. [18] Drugs that decrease breaking down of carbamazepine or otherwise increase its levels include erythromycin, [32] cimetidine, propoxyphene, and calcium channel blockers. [18] Grapefruit juice raises the bioavailability of carbamazepine by inhibiting the enzyme CYP3A4 in the gut wall and in the liver. [5] Lower levels of carbamazepine are seen when administered with phenobarbital, phenytoin, or primidone, which can result in breakthrough seizure activity. [33]
Valproic acid and valnoctamide both inhibit microsomal epoxide hydrolase (mEH), the enzyme responsible for the breakdown of the active metabolite carbamazepine-10,11-epoxide into inactive metabolites. [34] By inhibiting mEH, valproic acid and valnoctamide cause a build-up of the active metabolite, prolonging the effects of carbamazepine and delaying its excretion.
Carbamazepine, as an inducer of cytochrome P450 enzymes, may increase clearance of many drugs, decreasing their concentration in the blood to subtherapeutic levels and reducing their desired effects. [33] Drugs that are more rapidly metabolized with carbamazepine include warfarin, lamotrigine, phenytoin, theophylline, valproic acid, [18] many benzodiazepines, [35] and methadone. [36] Carbamazepine also increases the metabolism of the hormones in birth control pills and can reduce their effectiveness, potentially leading to unexpected pregnancies. [18]
Carbamazepine is a sodium channel blocker. [37] It binds preferentially to voltage-gated sodium channels in their inactive conformation, which prevents repetitive and sustained firing of an action potential. Carbamazepine has effects on serotonin systems but the relevance to its antiseizure effects is uncertain. There is evidence that it is a serotonin releasing agent and possibly even a serotonin reuptake inhibitor. [38] [39] [40] It has been suggested that carbamazepine can also block voltage-gated calcium channels, which will reduce neurotransmitter release. [41]
Carbamazepine is relatively slowly but practically completely absorbed after administration by mouth. Highest concentrations in the blood plasma are reached after 4 to 24 hours depending on the dosage form. Slow release tablets result in about 15% lower absorption and 25% lower peak plasma concentrations than ordinary tablets, as well as in less fluctuation of the concentration, but not in significantly lower minimum concentrations. [42] [43]
In the circulation, carbamazepine itself comprises 20 to 30% of total residues. The remainder is in the form of metabolites; 70 to 80% of residues is bound to plasma proteins. Concentrations in breast milk are 25 to 60% of those in the blood plasma. [43]
Carbamazepine itself is not pharmacologically active. It is activated, mainly by CYP3A4, to carbamazepine-10,11-epoxide, which is solely responsible for the drug's anticonvulsant effects. The epoxide is then inactivated by microsomal epoxide hydrolase (mEH) to carbamazepine-trans-10,11-diol and further to its glucuronides. Other metabolites include various hydroxyl derivatives and carbamazepine- N -glucuronide. [43]
The plasma half-life is about 35 to 40 hours when carbamazepine is given as single dose, but it is a strong inducer of liver enzymes, and the plasma half-life shortens to about 12 to 17 hours when it is given repeatedly. The half-life can be further shortened to 9–10 hours by other enzyme inducers such as phenytoin or phenobarbital. About 70% are excreted via the urine, almost exclusively in form of its metabolites, and 30% via the faeces. [42] [43]
Carbamazepine was discovered by chemist Walter Schindler at J.R. Geigy AG (now part of Novartis) in Basel, Switzerland, in 1953. [44] [45] 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. [44] It has been used as an anticonvulsant and antiepileptic in the United Kingdom since 1965, and has been approved in the United States since 1968. [1]
Carbamazepine was studied for bipolar disorder throughout the 1970s. [46]
Carbamazepine and its bio-transformation products have been detected in wastewater treatment plant effluent [47] : 224 and in streams receiving treated wastewater. [48] 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 commonly found in the environment, a 2014 review concluded 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." [47] : 227
Carbamazepine is available worldwide under many brand names including Tegretol. [49]
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Phenytoin (PHT), sold under the brand name Dilantin among others, is an anti-seizure medication. It is useful for the prevention of tonic-clonic seizures and focal seizures, but not absence seizures. The intravenous form, fosphenytoin, is used for status epilepticus that does not improve with benzodiazepines. It may also be used for certain heart arrhythmias or neuropathic pain. It can be taken intravenously or by mouth. The intravenous form generally begins working within 30 minutes and is effective for roughly 24 hours. Blood levels can be measured to determine the proper dose.
Valproate are medications primarily used to treat epilepsy and bipolar disorder and prevent migraine headaches. They are useful for the prevention of seizures in those with absence seizures, partial seizures, and generalized seizures. They can be given intravenously or by mouth, and the tablet forms exist in both long- and short-acting formulations.
Anticonvulsants 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, since many seem to act as mood stabilizers, and for the treatment of neuropathic pain. Anticonvulsants suppress the excessive rapid firing of neurons during seizures. Anticonvulsants also prevent the spread of the seizure within the brain.
Tramadol, sold under the brand name Ultram among others, is an opioid pain medication and a serotonin–norepinephrine reuptake inhibitor (SNRI) used to treat moderately severe pain. When taken by mouth in an immediate-release formulation, the onset of pain relief usually begins within an hour. It is also available by injection. It is available in combination with paracetamol (acetaminophen).
Topiramate, sold under the brand name Topamax among others, is a medication used to treat epilepsy and prevent migraines. It has also been used in alcohol dependence and essential tremor. For epilepsy this includes treatment for generalized or focal seizures. It is taken orally.
Lamotrigine, sold under the brand name Lamictal among others, is a medication used to treat epilepsy and stabilize mood in bipolar disorder. For epilepsy, this includes focal seizures, tonic-clonic seizures, and seizures in Lennox-Gastaut syndrome. In bipolar disorder, lamotrigine has not been shown to reliably treat acute depression in any groups except for the severely depressed; but for patients with bipolar disorder who are not currently symptomatic, it appears to reduce the risk of future episodes of depression.
Bupropion, formerly called amfebutamone, and sold under the brand name Wellbutrin among others, is an atypical antidepressant primarily used to treat major depressive disorder, seasonal affective disorder and to support smoking cessation. It is also popular as an add-on medication in the cases of "incomplete response" to the first-line selective serotonin reuptake inhibitor (SSRI) antidepressant. Bupropion has several features that distinguish it from other antidepressants: it does not usually cause sexual dysfunction, it is not associated with weight gain and sleepiness, and it is more effective than SSRIs at improving symptoms of hypersomnia and fatigue. Bupropion, particularly the immediate release formulation, carries a higher risk of seizure than many other antidepressants, hence caution is recommended in patients with a history of seizure disorder. The medication is taken by mouth.
Oxcarbazepine, sold under the brand name Trileptal among others, is a medication used to treat epilepsy. For epilepsy it is used for both focal seizures and generalized seizures. It has been used both alone and as add-on therapy in people with bipolar disorder who have had no success with other treatments. It is taken by mouth.
Levetiracetam, sold under the brand name Keppra among others, is a medication used to treat epilepsy. It is used for partial-onset, myoclonic, or tonic–clonic seizures and is taken either by mouth as an immediate or extended release formulation or by injection into a vein.
Clonazepam, sold under the brand name Klonopin among others, is a benzodiazepine medication used to prevent and treat anxiety disorders, seizures, bipolar mania, agitation associated with psychosis, obsessive–compulsive disorder (OCD), and akathisia. It is a long-acting tranquilizer of the benzodiazepine class. It possesses anxiolytic, anticonvulsant, sedative, hypnotic, and skeletal muscle relaxant properties. It is typically taken orally but is also used intravenously. Effects begin within one hour and last between eight and twelve hours in adults.
Primidone, sold under various brand names, is a barbiturate medication that is used to treat partial and generalized seizures and essential tremors. It is taken by mouth.
Vigabatrin, sold under the brand name Sabril among others, is a medication used in the management and treatment of infantile spasms and refractory complex partial seizures.
Trazodone, sold under many brand names, is an antidepressant medication, used to treat major depressive disorder, anxiety disorders, and insomnia. It is a phenylpiperazine compound of the serotonin antagonist and reuptake inhibitor (SARI) class. The medication is taken orally.
Clorazepate, sold under the brand name Tranxene among others, is a benzodiazepine medication. It possesses anxiolytic, anticonvulsant, sedative, hypnotic, and skeletal muscle relaxant properties. Clorazepate is an unusually long-lasting benzodiazepine and serves as a prodrug for the equally long-lasting desmethyldiazepam, which is rapidly produced as an active metabolite. Desmethyldiazepam is responsible for most of the therapeutic effects of clorazepate.
Felbamate is an anticonvulsant used in the treatment of epilepsy. It is used to treat partial seizures in adults and partial and generalized seizures associated with Lennox–Gastaut syndrome in children. However, an increased risk of potentially fatal aplastic anemia and/or liver failure limit the drug's usage to severe refractory epilepsy.
Brivaracetam, sold under the brand name Briviact among others, is a chemical analog of levetiracetam, a racetam derivative with anticonvulsant (antiepileptic) properties. It has been approved since 2016. It is marketed by the pharmaceutical company UCB. It is used to treat partial-onset seizures with or without secondary generalisation, in combination with other antiepileptic drugs.
Drug rash with eosinophilia and systemic symptoms or drug reaction with eosinophilia and systemic symptoms (DRESS), also termed drug-induced hypersensitivity syndrome (DIHS), is a rare reaction to certain medications. It involves primarily a widespread skin rash, fever, swollen lymph nodes, and characteristic blood abnormalities such as an abnormally high level of eosinophils, low number of platelets, and increased number of atypical white blood cells (lymphocytes). However, DRESS is often complicated by potentially life-threatening inflammation of internal organs and the syndrome has about a 10% mortality rate. Treatment consists of stopping the offending medication and providing supportive care. Systemic corticosteroids are commonly used as well but no controlled clinical trials have assessed the efficacy of this treatment.
Retigabine (INN) or ezogabine (USAN) is an anticonvulsant used as an adjunctive treatment for partial epilepsies in treatment-experienced adult patients. The drug was developed by Valeant Pharmaceuticals and GlaxoSmithKline. It was approved by the European Medicines Agency under the trade name Trobalt on March 28, 2011, and by the United States Food and Drug Administration (FDA), under the trade name Potiga, on June 10, 2011. Production was discontinued in June 2017.
Eslicarbazepine acetate (ESL), sold under the brand names Aptiom and Zebinix among others, is an anticonvulsant medication approved for use in Europe and the United States as monotherapy or as additional therapy for partial-onset seizures epilepsy.
An analgesic adjuvant is a medication that is typically used for indications other than pain control but provides control of pain (analgesia) in some painful diseases. This is often part of multimodal analgesia, where one of the intentions is to minimize the need for opioids.