1. Introduction
Carbamazepine, commonly marketed under brand names such as Tegretol, Carbatrol, and Epitol, is an anticonvulsant and mood-stabilising medication. It is primarily used to manage epilepsy, trigeminal neuralgia, and bipolar disorder. Carbamazepine works by reducing abnormal electrical activity in the brain and stabilising neuronal membranes.
2. Indications
- Approved Indications:
- Epilepsy: Partial seizures (simple and complex) and generalised tonic-clonic seizures.
- Trigeminal neuralgia.
- Acute manic or mixed episodes in bipolar disorder.
- Off-Label Uses:
- Neuropathic pain (e.g., diabetic neuropathy).
- Restless legs syndrome (RLS).
3. Dosage
- Epilepsy:
- Adults: 200 mg twice daily; increase by 200 mg/day weekly. Usual maintenance dose: 800–1200 mg/day in divided doses (maximum: 1600 mg/day).
- Children (6–12 years): 100 mg twice daily; increase by 100 mg/day weekly. Usual maintenance dose: 400–800 mg/day in divided doses.
- Trigeminal Neuralgia:
- Initial dose: 100 mg twice daily; increase by 200 mg/day weekly. Usual maintenance dose: 400–800 mg/day in divided doses.
- Bipolar Disorder:
- Initial dose: 200 mg twice daily; titrate based on response. Usual maintenance dose: 400–1600 mg/day.
4. Administration
- Take with food to minimise gastrointestinal discomfort.
- Extended-release tablets should be swallowed whole; do not crush or chew.
- Oral suspension should be shaken well before use.
5. Forms Available
- Tablets: 100 mg, 200 mg.
- Extended-release tablets: 200 mg, 400 mg.
- Oral suspension: 100 mg/5 mL.
6. Side Effects
6.1. Common Side Effects
- Dizziness.
- Drowsiness.
- Nausea and vomiting.
- Blurred vision or double vision.
6.2. Less Common Side Effects
- Dry mouth.
- Skin rash.
- Weight gain.
6.3. Rare but Serious Side Effects
- Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN).
- Aplastic anaemia and agranulocytosis.
- Hepatotoxicity.
- Hyponatraemia (SIADH).
7. Warnings
- Patients of Asian descent should be tested for HLA-B*1502 allele before initiating therapy due to the increased risk of SJS/TEN.
- Risk of suicidal thoughts and behaviour; monitor closely.
- Use with caution in patients with a history of bone marrow suppression.
8. Precautions
- Avoid abrupt discontinuation; taper doses gradually to prevent withdrawal seizures.
- Use with caution in patients with hepatic or renal impairment.
- Avoid alcohol, as it may enhance CNS depression.
9. Interactions
- Drug-Drug Interactions:
- Strong enzyme inducer; may reduce the efficacy of oral contraceptives, warfarin, and other drugs metabolised by CYP3A4.
- Increased risk of toxicity with macrolide antibiotics (e.g., erythromycin) and azole antifungals.
- Risk of sedation when combined with other CNS depressants.
- Drug-Food Interactions:
- Avoid grapefruit juice, as it can increase carbamazepine levels and toxicity risk.
10. Monitoring Parameters
- Baseline and periodic complete blood count (CBC) to monitor for blood dyscrasias.
- Liver function tests (LFTs) and renal function periodically.
- Serum carbamazepine levels (therapeutic range: 4–12 mcg/mL).
- Electrolytes, particularly sodium, to monitor for hyponatraemia.
11. Use in Children
- Approved for use in children aged 6 years and older for epilepsy.
- Dosage must be weight-adjusted, and side effects should be closely monitored.
12. Use in Pregnancy
- Category D: Associated with an increased risk of congenital malformations (e.g., neural tube defects).
- Use only if the potential benefit outweighs the risk.
- Women of childbearing potential should use effective contraception.
13. Use in Elderly
- Use with caution due to an increased risk of dizziness, drowsiness, and hyponatraemia.
- Monitor renal function and serum sodium levels closely.
14. Use in Kidney Disease
- Use with caution in patients with renal impairment.
- Adjust dosage as necessary based on renal function and serum drug levels.
15. Use in Liver Disease
- Use with caution in patients with hepatic impairment.
- Regular monitoring of liver enzymes is essential.
16. Patient Counselling Points
- Take medication exactly as prescribed, with food if needed to avoid stomach upset.
- Avoid driving or operating machinery until you know how the medication affects you.
- Do not abruptly stop taking carbamazepine without consulting your doctor.
- Report any unusual symptoms, such as rash, fever, sore throat, or unusual bleeding, immediately.
- Women should use effective contraception, as carbamazepine can reduce the efficacy of hormonal contraceptives.
17. Table of Brand Names, Manufacturers, and Prices
Brand Name | Manufacturer | Price (USD) |
---|---|---|
Tegretol | Novartis | $30–50 (30 tablets, 200 mg) |
Carbatrol | Shire Pharmaceuticals | $50–80 (30 ER capsules, 200 mg) |
Epitol | Various | $20–40 (30 tablets, 200 mg) |
Generic Options | Various | $10–20 (30 tablets, 200 mg) |
18. FAQs (15 Questions)
- What is carbamazepine used for?
It is used to treat epilepsy, trigeminal neuralgia, and bipolar disorder. - How does carbamazepine work?
It stabilises neuronal membranes by inhibiting voltage-gated sodium channels, reducing abnormal electrical activity. - What are the common side effects of carbamazepine?
Dizziness, drowsiness, nausea, and blurred vision. - Can carbamazepine cause a skin rash?
Yes, it can cause mild rashes or serious reactions like Stevens-Johnson syndrome (SJS). - Is carbamazepine safe during pregnancy?
It carries risks of congenital malformations and should be used only if necessary under medical supervision. - How should carbamazepine be taken?
Take it with food to reduce stomach upset and swallow extended-release tablets whole. - Can carbamazepine interact with other medications?
Yes, it interacts with many drugs, including oral contraceptives, warfarin, and macrolide antibiotics. - Can I drink alcohol while on carbamazepine?
No, alcohol can increase the risk of drowsiness and other side effects. - What should I do if I miss a dose?
Take it as soon as you remember, but skip it if it’s close to the next dose. Do not double up. - How long does carbamazepine take to work?
Effects may take days to weeks for seizure control or mood stabilisation. - Does carbamazepine cause weight gain?
Weight gain is a less common side effect but can occur. - What should I avoid while taking carbamazepine?
Avoid grapefruit juice and any activities requiring alertness until you know how it affects you. - Can carbamazepine cause low sodium levels?
Yes, it can cause hyponatraemia, especially in elderly patients. - How is carbamazepine monitored?
Through blood tests to check drug levels, liver function, and blood cell counts. - Is carbamazepine addictive?
No, it is not addictive, but it must be taken regularly to maintain therapeutic effects.