carbamazepine

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n.

An anticonvulsant drug, C₁₅H₁₂N₂O, used in the treatment of certain forms of epilepsy and to relieve pain associated with trigeminal neuralgia.

[CARBAM(OYL) + (benz)azepine, one of its constituents (BENZ(O)– + AZ(O)– + EP(OXIDE) + –INE²).]

Definition

Carbamazepine is an antiepileptic drug used to reduce or suppress seizures. The medication is also commonly prescribed to relieve certain neurogenic pain such as trigeminal neuralgia. This drug decreases abnormal electrical impulses through nerve cell pathways by inhibiting the activity of sodium channels in neurons. Consequently, it blocks the repetitive impulses that trigger seizures. In the United States, brand names for carbamazepine include Tegretol, Carbatrol, and Epitol. This medication is classified into the following categories: anticonvulsant, antimanic, and antineuralgic.

Purpose

Due to its high efficacy, carbamazepine is in many cases a first-line treatment for epilepsy, and is also frequently prescribed to treat acute neuralgias such as trigeminal neuralgia. Sometimes the drug is also used to improve bipolar disorder symptoms, especially during the manic phase of this disease.

Description

Carbamazepine is a lipid-soluble substance metabolized in the liver by enzymes of the P-450 family and therefore, its chronic administration may induce liver toxicity, especially in patients with reduced liver function. In contrast, persons whose P-450 enzymes are very efficient and metabolize the drug rapidly tend to have decreased carbamazepine half-life and therefore, reduced efficacy of the medication. The body slowly absorbs carbamazepine and the drug easily passes through the blood-brain barrier. It is rapidly transported into the central nervous system (CNS), where it exerts a depressant effect.

Recommended dosage

For treatment of seizures, the usual initial dose of carbamazepine for adults and children over 12 years of age is 200 milligrams, taken twice daily. The prescribing physician may increase the dosage in weekly intervals until optimum seizure control is achieved. Dosages generally do not exceed a range of 1000–1200 milligrams (mg) per day. For the treatment of trigeminal neuralgia, daily dosages usually range from 800–1200 mg per day during the stage of acute pain and 400–800 mg per day for preventative therapy.

Precautions

The ingestion of alcoholic drinks during carbamazepine therapy is contraindicated because both substances may potentiate (increase) the effects of the other. Other depressants of the central nervous system such as antihistamines, analgesic drugs, muscle relaxants, and tranquilizers, are also potentiated when used with carbamazepine or other antiepileptic medications. Diabetic patients should be monitored during the administration of this drug since it interferes with glucose blood levels. The drug should not be taken during pregnancy due to the absence of safety clinical studies for pregnant women. Tests in animals have shown that carbamazepine causes developmental defects in embryos when administered in high doses. As the drug is found in breast milk, the use of this medication is also contraindicated during breast-feeding. Carbamazepine may interfere with several biomarkers used in medical laboratory tests, and persons taking the medication should report its intake before blood or urine samples are collected for analysis.

Side effects

The intensity of side effects (or adverse effects) of carbamazepine is dose-dependant. Among the mild adverse effects observed during chronic administration of this medication are drowsiness, vertigo, fatigue, blurred vision, gastritis, constipation, aching muscles or joints, skin sensitivity to solar radiation, loss of appetite, and dry mouth. In most patients, these side effects are mild and tend to decrease in intensity or to completely disappear within a few days of treatment. However, if they are particularly intense or do persist for two or more weeks they should be reported to the physician.

Nevertheless, elderly patients or patients exhibiting one or more severe symptoms in association with carbamazepine intake such as chest pain, blurred vision, mental confusion or hallucinations, numbness, tachycardia, depression or marked mood changes, urinary retention or excessive diuresis, peripheral edema, severe diarrhea or vomiting, should report such symptoms to their physicians as soon as possible.

Moreover, immediate medical attention may be required in the presence of one or more of the following adverse effects: presence of blood in the urine or urine with a dark color, black tarry stools or pale stools, unusual bleeding or bruising, skin rashes, ulcers or white spots in the mouth or lips, chills and fever, shallow or uneasy breathing or wheezing chest, jaundice, arrhythmia, sudden blood pressure fall or unusual high blood pressure, cough and/or sore throat. These side effects could indicate the presence of a potentially serious blood disorder.

Interactions

The use of carbamazepine reduces the effectiveness of oral contraceptives and also reduces the effects of corticosteroids. The concomitant use of one of the following drugs inhibits the metabolism of carbamazepine, thereby decreasing its effectiveness: cimetidine, erythromycin, isoniazid, diltiazem, and propoxyphene. Conversely, carbamazepine decreases the plasma levels of phenytoin, another antiepileptic drug. Clarithromycin, an antibiotic, increases the blood levels of carbamazepine and thus, increases the risk of adverse effects.

The use of particular antidepressant medicines known as monoamine oxidase (MAO) inhibitors during carbamazepine therapy, or within the previous two weeks before initiating carbamazepine therapy may increase the risk of fever, severe high blood pressure, stroke, and convulsions. Therefore, an interval of at least two weeks is recommended between the administration of these two classes of drugs.

Resources

BOOKS

Champe, Pamela C., and Richard A. Harvey, eds. Pharmacology, 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2000.

OTHER

"Carbamazepine." Medline Plus. National Library of Medicine. (January 1, 2003) (March 20, 2004). http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a682237.html.

National Institute of Neurological Disorders and Stroke. NINDS Trigeminal Neuralgia Information Page. (May 29, 2001) (March 20, 2004). http://www.ninds.nih.gov/health_and_medical/disorders/trigemin_doc.htm.

ORGANIZATIONS

Epilepsy Foundation. 4351 Garden City Drive, Landover, MD 20785-7223. (800) 332-1000. http://www.epilepsyfoundation.org.

National Institute of Neurological Disorders and Stroke. P.O. Box 5801, Bethesda, MD, 20892-2540. (301) 496-5751 or (800) 352-9424. http://www.ninds.nih.gov/. contact_us.htm> or http://www.ninds.nih.gov/index.htm.

Sandra Galeotti

Key Terms: Anticonvulsant, Bipolar disorder, Bone marrow.

Definition

Carbamazepine (Tegretol, Carbatrol) may be administered to cancer patients as a pain medicine.

Purpose

Carbamazepine is given to cancer patients primarily as a pain medication. The drug may, for example, be prescribed for stabbing pain that moves along a nerve. For noncancer patients, it is often used to treat epilepsy or bipolar disorder (manic-depressive illness). Carbamazepine is classified as an anticonvulsant because it is often given to control seizures.

Description

Carbamazepine suppresses some of the activities of the nerves. It does this by delaying the amount of time it takes for certain passageways in the nerves to recover after they have sent out a message.

Recommended Dosage

Carbamazepine comes in several forms. There are 200 mg tablets, 100 mg chewable tablets, and a liquid containing 20 mg per milliliter that may be swallowed. There are extended-release tablets of carbamazepine containing 100, 200, or 400 mg and extended release capsules of the medication containing 200 and 300 mg.

Some authorities recommend starting with 100 to 200 mg twice a day. This strategy helps to minimize side effects. Then, the dose may be gradually increased every week. Adults may eventually receive 600 to 1200 mg a day, while 20 to 30 mg per kg of body weight per day is appropriate for children.

Side Effects

Carbamazepine may exhibit side effects to the nervous system, for example, drowsiness, dizziness, blurred vision, unsteadiness, depression, impaired concentration, and headache. Patients should be cautious about operating machinery or performing tasks requiring alertness until tolerant of the side effects. After several weeks of treatment, these side effects may disappear. To minimize these side effects, doctors may start carbamazepine at a low dose and may recommend that it be taken before bedtime. As carbamazepine may cause stomach upset and nausea, the medicine should be taken with meals.

Effects of carbamazepine may include bone marrow suppression, which involves a low white blood cell and platelet count, but this is usually not severe. Very rarely, a dangerous anemia may occur during carbamazepine therapy. Blood counts should be monitored for patients using this drug. Some patients with previously diagnosed depression of the bone marrow should not be given carbamazepine.

Carbamazepine may cause birth defects and should be avoided in women who are pregnant. In addition, women sometimes develop hypersensitivity reactions to carbamazepine during pregnancy. An appropriate contraceptive method should be used while on carbamazepine. Carbamazepine can cross into breast milk and should be avoided in women who are breastfeeding. Carbamazepine may also cause rash or sensitivity to the sun.

Interactions

Carbamazepine may affect the activity of other medicines, for example, oral contraceptives, warfarin, theophylline, doxycycline, haloperidol, corticosteroids, valproate, clonazepam, ethosuximide, lamotrigine, felbamate, and thyroid hormones. Oral contraceptives may become less effective if a patient is taking carbamazepine. Some doctors recommend that the form of birth control pill be altered or that a different method of contraception be used. If phenytoin and phenobarbital are taken at the same time as carbamazepine, the capacity of carbamazepine to interact with additional medications may increase. Side effects may occur if a patient is taking carbamazepine and one of the following medications simultaneously: danazol, dextropropoxyphene, erythromycin, clarithromycin, isoniazid, verapamil, or diltiazem. Due to the numerous potential of interactions with other drugs, patients should consult with their physician or pharmacist prior to starting any new medications either bought over the counter or initiated by another physician. Patients taking carbamazepine should not drink grapefruit juice.

Carbamazepine sometimes complicates the treatment of brain tumors because it can lower the blood level of other drugs given to stop the growth of the tumor. Researchers are currently exploring the use of newer anticonvulsant drugs in treating patients with brain tumors.

Carbamazepine has also been reported to interact with certain herbs, including evening primrose (Oenothera biennis), gingko (Gingko biloba), and wormwood (Artemisia pontica). Patients should always tell their doctor about any herbal preparations they may be taking as well as other prescription medications.

Resources

Periodicals

Deering, S. H., K. Thompson, J. Taylor, and N. Hueppchen. "Anticonvulsant Hypersensitivity Reaction in Pregnancy." Obstetrics and Gynecology 102 (November 2003): 1215–1217.

Misra, U. K., J. Kalita, and C. Rathore. "Phenytoin and Carbamazepine Cross-Reactivity: Report of a Case and Review of Literature." Postgraduate Medical Journal 79 (December 2003): 703–704.

Vecht, C. J., G. L. Wagner, and E. B. Wilms. "Treating Seizures in Patients with Brain Tumors: Drug Interactions Between Antiepileptic and Chemotherapeutic Agents." Seminars in Oncology 30 (December 2003): 49–52.

Wang, P. W., T. A. Ketter, O. V. Becker, and C. Nowakowska. "New Anticonvulsant Medication Uses in Bipolar Disorder." CNS Spectrums 8 (December 2003): 930–2, 941–7.

Organizations

United States Food and Drug Administration (FDA). 5600 Fishers Lane, Rockville, MD 20857-0001. (888) INFO-FDA (463-6332). .

—Bob Kirsch; Rebecca J. Frey, PhD

n

trade names: Apo-Carbamazepine, Epitol, Novo Carbamaz; drug class: anticonvulsant; action: inhibits nerve impulses by limiting influx of sodium ions across cell membrane in motor cortex; uses: tonic-clonic complex-partial, mixed seizures, a specific analgesic for trigeminal neuralgia, sometimes used in the treatment of herpes zoster.

Brand names: Carbatrol®Epitol®Equetro™Tegretol®Tegretol®-XR

Chemical formula:

Drug Forms:
• Carbamazepine Chewable tablet (below)
• Carbamazepine Oral capsule, extended-release
• Carbamazepine Oral suspension
• Carbamazepine Oral tablet
• Carbamazepine tablets or chewable tablets
• Carbamazepine extended-release tablets or capsules
• Carbamazepine Oral capsule, extended-release [Bipolar Disorder]
• Carbamazepine Oral tablet, extended-release

Español:
• Carbamazepina, Tableta masticable
• Carbamazepina, Cápsula oral de liberación prolongada
• Carbamazepina, Suspensión oral
• Carbamazepina, Tableta oral
• Tabletas o tabletas masticables de carbamazepina
• Cápsulas o tabletas de liberación prolongada de carbamazepina
• Carbamazepina, Cápsula oral de liberación prolongada [Trastorno Bipolar]
• Carbamazepina, Tableta oral de liberación prolongada

Carbamazepine Chewable tablet

What is this medicine?

CARBAMAZEPINE is used to control seizures caused by certain types of epilepsy. This medicine is also used to treat nerve related pain. It is not for common aches and pains.

This medicine may be used for other purposes; ask your health care provider or pharmacist if you have questions.

What should I tell my health care provider before I take this medicine?

They need to know if you have any of these conditions:
•Asian ancestry
•bone marrow disease
•glaucoma
•heart disease or irregular heartbeat
•kidney disease
•liver disease
•porphyria
•psychotic disorders
•suicidal thoughts, plans, or attempt; a previous suicide attempt by you or a family member
•an unusual or allergic reaction to carbamazepine, tricyclic antidepressants, phenytoin, phenobarbital or other medicines, foods, dyes, or preservatives
•pregnant or trying to get pregnant
•breast-feeding

How should I use this medicine?

Take this medicine by mouth. Chew it or swallow whole. Follow the directions on the prescription label. Take this medicine with food. Take your doses at regular intervals. Do not take your medicine more often than directed. Do not stop taking this medicine except on the advice of your doctor or health care professional.

Talk to your pediatrician regarding the use of this medicine in children. While this drug may be prescribed for children 6 years of age and younger for selected conditions, precautions do apply.

Overdosage: If you think you have taken too much of this medicine contact a poison control center or emergency room at once.
NOTE: This medicine is only for you. Do not share this medicine with others.

What may interact with this medicine?

Do not take this medicine with any of the following medications:
•delavirdine
•MAOIs like Carbex, Eldepryl, Marplan, Nardil, and Parnate
•nefazodone
•oxcarbazepine

This medicine may also interact with the following medications:
•acetaminophen
•acetazolamide
•barbiturate medicines for inducing sleep or treating seizures, like phenobarbital
•certain antibiotics like clarithromycin, erythromycin or troleandomycin
•cimetidine
•cyclosporine
•danazol
•dicumarol
•doxycycline
•female hormones, including estrogens and birth control pills
•grapefruit juice
•isoniazid, INH
•levothyroxine and other thyroid hormones
•lithium and other medicines to treat mood problems or psychotic disturbances
•loratadine
•medicines for angina or high blood pressure
•medicines for cancer
•medicines for depression or anxiety
•medicines for sleep
•medicines to treat fungal infections, like fluconazole, itraconazole or ketoconazole
•medicines used to treat HIV infection or AIDS
•methadone
•niacinamide
•praziquantel
•propoxyphene
•rifampin or rifabutin
•seizure or epilepsy medicine
•steroid medicines such as prednisone or cortisone
•theophylline
•tramadol
•warfarin

This list may not describe all possible interactions. Give your health care provider a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.

What should I watch for while using this medicine?

Visit your doctor or health care professional for a regular check on your progress. Do not change brands or dosage forms of this medicine without discussing the change with your doctor or health care professional. If you are taking this medicine for epilepsy (seizures) do not stop taking it suddenly. This increases the risk of seizures. Wear a Medic Alert bracelet or necklace. Carry an identification card with information about your condition, medications, and doctor or health care professional.

You may get drowsy, dizzy, or have blurred vision. Do not drive, use machinery, or do anything that needs mental alertness until you know how this medicine affects you. To reduce dizzy or fainting spells, do not sit or stand up quickly, especially if you are an older patient. Alcohol can increase drowsiness and dizziness. Avoid alcoholic drinks.

Birth control pills may not work properly while you are taking this medicine. Talk to your doctor about using an extra method of birth control.

This medicine can make you more sensitive to the sun. Keep out of the sun. If you cannot avoid being in the sun, wear protective clothing and use sunscreen. Do not use sun lamps or tanning beds/booths.

The use of this medicine may increase the chance of suicidal thoughts or actions. Pay special attention to how you are responding while on this medicine. Any worsening of mood, or thoughts of suicide or dying should be reported to your health care professional right away.

What side effects may I notice from receiving this medicine?

Side effects that you should report to your doctor or health care professional as soon as possible:
•allergic reactions like skin rash, itching or hives, swelling of the face, lips, or tongue
•breathing problems
•change in vision
•confusion
•dark urine
•fast or irregular heartbeat
•fever or chills, sore throat
•mouth ulcers
•pain or difficulty passing urine
•redness, blistering, peeling or loosening of the skin, including inside the mouth
•ringing in the ears
•seizures
•stomach pain
•swollen joints or muscle/joint aches and pains
•unusual bleeding or bruising
•unusually weak or tired
•vomiting
•worsening of mood, thoughts or actions of suicide or dying
•yellowing of the eyes or skin

Side effects that usually do not require medical attention (report to your doctor or health care professional if they continue or are bothersome):
•clumsiness or unsteadiness
•diarrhea or constipation
•headache
•increased sweating
•nausea

This list may not describe all possible side effects. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Where should I keep my medicine?

Keep out of reach of children.

Store at room temperature below 30 degrees C (86 degrees F). Keep container tightly closed. Protect from moisture. Throw away any unused medicine after the expiration date.

Last updated: 1/19/2005 5:10:00 PM

Important Disclaimer: The drug information provided here is for educational purposes only. It is intended to supplement, not substitute for, the diagnosis, treatment and advice of a medical professional. This drug information does not cover all possible uses, precautions, side effects and interactions. It should not be construed to indicate that this or any drug is safe for you. Consult your medical professional for guidance before using any prescription or over the counter drugs.

An anticonvulsant and analgesic used in the treatment of pain and for control of partial or generalized tonic–clonic seizures, often in combination with other drugs.

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