Carbamazepine

Therapeutic Class
Anticonvulsant
Indications

Partial seizures with complex symptomatology (psychomotor, temporal lobe), generalized tonic-clonic seizures (grand mal), mixed seizure patterns, trigeminal neuralgia,  Acute manic and mixed episodes associated with bipolar 1 disorder, Treatment of restless leg syndrome and post-traumatic stress disorders

Adult Doses

Epilepsy
Oral: Initially, 100-200 mg once or bid gradually increased by increments of 100-200 mg every 2 wk. Maintenance: 0.8-1.2 g daily in divided doses.
Maximum recommended dose: 1600 mg/day; however, some patients have required up to 1.6-2.4 g/day
Rectal: 250 mg every 6 hr for patients incapable of oral treatment.

Trigeminal or glossopharyngeal neuralgia
Oral: Initially, 100 mg once or bid gradually increased as necessary.
Maintenance: 400-800 mg daily in 2-4 divided doses. Max: 1.2 g daily.

Prophylaxis of bipolar disorder
Oral: Initially, 400 mg daily in divided doses gradually increased if necessary. Maintenance: 400-600 mg daily. Max: 1.6 g daily.

Pediatric Doses

Epilepsy: Oral:

Children <6 years:
Initial: 10-20 mg/kg/day divided twice or 3 times daily as tablets or 4 times/day as suspension; increase dose every week until optimal response and therapeutic levels are achieved.
Maintenance dose: Divide into 3-4 doses daily (tablets or suspension);
maximum recommended dose: 35 mg/kg/day

Children 6-12 years:
Initial: 200 mg/day in 2 divided doses (tablets or extended release tablets) or 4 divided doses (oral suspension); increase by up to 100 mg/day at weekly intervals using a twice daily regimen of extended release tablets or 3-4 times daily regimen of other formulations until optimal response and therapeutic levels are achieved.
Maintenance: Usual: 400-800 mg/day; maximum recommended dose: 1000 mg/day

Children >12 years: Refer to adult dosing.
Maximum recommended doses:
Children 12-15 years: 1000 mg/day
Children >15 years: 1200 mg/day

Doses in Renal impairment

Administer 75% of dose

Doses in Hepatic impairment

Use with caution in hepatic impairment; metabolized primarily in the liver

Contraindications

Hypersensitivity; bone marrow depression; porphyria, pregnancy.

Boxed Warning

Potentially fatal blood cell abnormalities have been reported following treatment.

Patients of Asian descent should be screened for the variant HLA-B*1502 allele prior to initiating therapy.

Warnings / Precautions

Lactation; CV disease, hepatic or renal disorders, history of blood disorders or haematological reactions to other drugs; glaucoma; skin disorders; elderly, patients on MAO inhibitors; abrupt withdrawal of treatment.

Adverse Reactions

Dizziness, drowsiness, ataxia; dry mouth, abdominal pain, nausea, vomiting, anorexia; leucopenia, proteinuria, renal failure, heart failure and hyponatraemia.
Potentially Fatal: Agranulocytosis, aplastic anaemia, hepatic failure, severe exfoliative dermatitis and Stevens-Johnson syndrome.

Drug Interactions

Reduces tolerance to alcohol; shortens T1/2 of doxycycline. Decreased efficacy of oral contraceptives when used with carbamazepine. Increased plasma concentrations of carbamazepine by propoxyphene. Serum level decreases with phenytoin, phenobarbital, primidone.
Potentially Fatal: Neurotoxic reactions when combined with lithium.
See Below for More carbamazepine Drug Interactions

Lab Interactions

False-positive result in urine sugar, elevated serum alkaline phosphatase and serum bilirubin values.

Food Interactions

Ethanol: May increase CNS depression; monitor for increased effects with coadministration. Caution patients about effects.

Food: Carbamazepine serum levels may be increased if taken with food. Carbamazepine serum concentration may be increased if taken with grapefruit juice; avoid concurrent use.

Herb/Nutraceutical: Avoid evening primrose (seizure threshold decreased). Avoid valerian, St John's wort, kava kava, gotu kola (may increase CNS depression).

Mechanism of Actions

In addition to anticonvulsant effects, carbamazepine has anticholinergic, antineuralgic, antidiuretic, muscle relaxant, antimanic, antidepressive, and antiarrhythmic properties; may depress activity in the nucleus ventralis of the thalamus or decrease synaptic transmission or decrease summation of temporal stimulation leading to neural discharge by limiting influx of sodium ions across cell membrane or other unknown mechanisms; stimulates the release of ADH and potentiates its action in promoting reabsorption of water; chemically related to tricyclic antidepressants

Metabolism

Substrate of CYP2C8 (minor), 3A4 (major); Induces CYP1A2 (strong), 2B6 (strong), 2C8 (strong), 2C9 (strong), 2C19 (strong), 3A4 (strong), P-glycoprotein

Pharmacodynamics

Absorption: Slow

Distribution: Vd: Neonates: 1.5 L/kg; Children: 1.9 L/kg; Adults: 0.59-2 L/kg

Protein binding: Carbamazepine: 75% to 90%, may be decreased in newborns; Epoxide metabolite: 50%

Metabolism: Hepatic via CYP3A4 to active epoxide metabolite; induces hepatic enzymes to increase metabolism

Bioavailability: 85%

Half-life elimination: Note: Half-life is variable because of autoinduction which is usually complete 3-5 weeks after initiation of a fixed carbamazepine regimen.

Carbamazepine: Initial: 25-65 hours; Extended release: 35-40 hours; Multiple doses: Children: 8-14 hours; Adults: 12-17 hours

Epoxide metabolite: Initial: 25-43 hours

Time to peak, serum: Unpredictable:

Immediate release: Suspension: 1.5 hour; tablet: 4-5 hours

Extended release: Carbatrol®, Equetro®: 12-26 hours (single dose), 4-8 hours (multiple doses); Tegretol®-XR: 3-12 hours

Excretion: Urine 72% (1% to 3% as unchanged drug); feces (28%)

Monitoring

CBC with platelet count, reticulocytes, serum iron, lipid panel, liver function tests, urinalysis, BUN, serum carbamazepine levels, thyroid function tests, serum sodium; pregnancy test; ophthalmic exams (pupillary reflexes); observe patient for excessive sedation, especially when instituting or increasing therapy; signs of rash; HLA-B*1502 genotype screening prior to therapy initiation in patients of Asian descent; suicidality (eg, suicidal thoughts, depression, behavioral changes)

Administration

Should be taken with food. (Avoid grapefruit juice.)

Pregnancy Category

D: Drug Pregnancy Category There is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience or studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.

Lactation

Enters breast milk/not recommended

Storage Conditions

Oral: Store below 30°C Rectal: Store below 30°C

ATC Classification
N03AF01 - carbamazepine ; Belongs to the class of carboxamide derivatives antiepileptic.
GenericPedia Classification
  • Storage

    Oral: Store below 30°C Rectal: Store below 30°C

    Available As
  • Carbamazepine 100 mg
  • Carbamazepine 200 mg
  • Carbamazepine 300 mg
  • Carbamazepine 400 mg
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