Carbamazepine: 7 things you should know
Medically reviewed by Carmen Fookes, BPharm. Last updated on Apr 10, 2020.
1. How it works
- Carbamazepine is an anticonvulsant (a drug that stops seizures). Experts believe it works by dampening down electrical impulses and reducing the subsequent firing of the nerve; however, the exact mechanism of action is unknown.
- Carbamazepine is not chemically related to any other available anticonvulsant or medicine used in the treatment of nerve disorders.
- Carbamazepine belongs to the class of medicines known as dibenzazepine anticonvulsants.
- Carbamazepine is used for the treatment of seizure disorders such as generalized tonic-clonic seizures and partial seizures with complex symptomatology (for example generated from psychomotor or temporal lobe epilepsy).
- Carbamazepine may also be used to treat mixed seizure types or other types of partial or generalized seizures; however, it appears ineffective for absence seizures.
- Carbamazepine also relieves nerve pain associated with trigeminal neuralgia and diabetic neuropathy. Some people with glossopharyngeal neuralgia may also experience benefit with carbamazepine.
- May be used alone or in combination with other agents.
- Carbamazepine can be used in the treatment of bipolar disorder as a mood stabilizer.
- Blood levels of carbamazepine are able to be monitored. This can improve the safety and effectiveness of the drug, verify compliance, and uncover a reason for increased seizure frequency or side effects.
- Carbamazepine is not associated with any psychological or physical dependence and there is no potential for abuse.
- Generic carbamazepine is available.
If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:
- Dizziness, drowsiness, nausea or vomiting and unsteadiness are the most common side effects reported.
- May not be suitable for everybody including those with a history of bone marrow depression, cardiac conduction disturbances, hepatic porphyria, increased intraocular pressure (unless closely monitored), or known sensitivity to carbamazepine or tricyclic antidepressants. Sensitivity reactions may be greater in those with who have inherited the HLA-A 3101 gene (more prevalent in people of Asian, Arabic, Native American or Southern Indian descent).
- Carbamazepine should not be stopped suddenly; rather, it should be withdrawn slowly on a doctor's advice. Sudden withdrawal may precipitate status epilepticus (a prolonged, potentially life-threatening seizure).
- Rarely, serious but sometimes fatal dermatological reactions (such as Toxic Epidermal Necrolysis and Stevens-Johnson syndrome) may occur. The risk is greater in Caucasians and those of Asian descent, particularly people with the genetic variant HLA-B 1502. Screening for HLA-B 1502 should occur in those genetically at-risk and patients testing positive for the allele should not be treated with carbamazepine.
- Rarely, potentially fatal bone marrow depression (resulting in aplastic anemia or agranulocytosis) may occur; however, the risk is extremely low although people exhibiting decreased platelet or white blood cell counts should be monitored closely and carbamazepine discontinued if the condition worsens.
- Anticonvulsants (including carbamazepine) have been associated with an increased risk of suicidal thoughts and behaviors. These may occur as early as one week after starting treatment with carbamazepine. If your mood becomes depressed, tell your doctor.
- May cause hyponatremia (low sodium levels); the risk is higher in the elderly, in patients treated with diuretics, and with increasing dosages of carbamazepine.
- May interfere with some thyroid function tests and pregnancy tests.
- May interact with alcohol and a number of drugs including other anticonvulsants, antipsychotics, antidepressants, and warfarin.
Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.
- Available as a suspension, conventional-release tablets, and extended-release tablets. More frequent dosing of the suspension and conventional tablets provide more stable levels of carbamazepine in the body; follow your doctor's dosing instructions exactly.
- Your doctor may need to conduct some baseline tests to determine how well-functioning your bone marrow is or if you are genetically at risk of any serious reactions with carbamazepine. Other tests (such as eye examinations, blood tests, urine tests) may be needed periodically while you are taking carbamazepine.
- See your doctor if you develop a fever, sore throat, rash, mouth ulcers, swollen lymph nodes, begin to bruise easily, or develop petechiae (pinpoint, round blood spots on the skin) or any unusual skin reaction. Also report any unexplained weight loss, nausea or vomiting, or jaundice (yellowing of the skin). These symptoms may signal a serious reaction to carbamazepine and should be reported even if mild or occurring after extended use.
- Carbamazepine may affect your judgment and slow your reaction time - be cautious when driving a vehicle or operating machinery until you know how carbamazepine affects you.
- Do not drink alcohol while you are taking carbamazepine because this may increase the sedative effect of carbamazepine.
- Tell your doctor if you experience any symptoms of hyponatremia (such as a headache, confusion, new or increased seizure frequency, weakness, or unsteadiness which could lead to falls).
- Tell your doctor if your mood becomes depressed, or you start having thoughts of suicide or self-harm while taking carbamazepine.
- Talk to a pharmacist or doctor before taking any other medications with carbamazepine because some of these (including those bought over-the-counter) may be incompatible with it.
6. Response and Effectiveness
- Peak plasma levels of carbamazepine are reached after approximately 1.5 hours following the suspension, compared to 4 to 5 hours following administration of the conventional release tablets, and 3 to 12 hours following administration of the extended-release tablets. Usual adult therapeutic levels (the level needed for carbamazepine to be effective) are between 4 and 12 mcg/mL.
- Interactions with other drugs may increase or decrease carbamazepine levels.
- Carbamazepine also induces its own metabolism, which means that the length of time it stays in the body for shortens the longer you take the drug. This is called autoinduction and it takes three to five weeks of a fixed dosing regimen before it is complete.
- In children, plasma levels of carbamazepine poorly correlate with the dosage of carbamazepine. Carbamazepine is more rapidly metabolized in children to its active metabolite, which has been found in animal studies to be as potent as carbamazepine itself.
Medicines that interact with carbamazepine may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with carbamazepine. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.
Common medications that may interact with carbamazepine include:
- antibiotics such as clarithromycin, doxycycline, erythromycin
- anticonvulsants such as carbamazepine, phenytoin, and phenobarbitone
- antidepressants, such as desipramine, doxepin, isocarboxazid, nefazodone, phenelzine or venlafaxine
- antifungals, such as fluconazole, itraconazole or griseofulvin
- antihistamines, such as azelastine, cetirizine, or levocetirizine
- antipsychotics, such as aripiprazole, clozapine, haloperidol, or quetiapine
- antivirals, such as boceprevir, darunavir, raltegravir, or elvitegravir
- cancer medications, such as acalabrutinib, or cyclophosphamide
- corticosteroids such as betamethasone or methylprednisolone
- diuretics, such as furosemide
- folic acid
- heart medications, such as amiodarone, amlodipine, diltiazem, or nifedipine
- HIV medications such as indinavir and ritonavir
- estrogen or progestin-containing oral contraceptives and hormonal treatments
- medications that cause drowsiness, such as benzodiazepines, sedating antihistamines, and sleeping pills
- medications that reduce the risk of blood clotting, such as apixaban or dabigatran
- muscle relaxants, such as baclofen
- opioid analgesics such as buprenorphine, codeine, fentanyl, oxycodone, and morphine
- Parkinson's disease medications, such as selegiline
Alcohol may worsen the side effects of carbamazepine such as drowsiness, dizziness, and liver toxicity.
Note that this list is not all-inclusive and includes only common medications that may interact with carbamazepine. You should refer to the prescribing information for carbamazepine for a complete list of interactions.
Carbamazepine Revised 01/2020. Drugs.com https://www.drugs.com/ppa/carbamazepine.html
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use carbamazepine only for the indication prescribed.
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