Carbamazepine

Question 1

Therapeutic Range:

Answer 1

4 to 12mg/L (20 to 50 micromol/litre)

Question 2

Monitoring

Answer 2

Full blood count, renal function, liver function

Question 3

Warning Signs

Answer 3

• Toxicity - incoordination, blurred vision, diplopia, drowsiness, nystagmus, ataxia, arrhythmias,
nausea and vomiting, diarrhoea, hyponatraemia
• Blood disorders e.g. leucopenia, thrombocytopenia (fever, sore throat, unexplained bruising
or bleeding)
• Skin disorders e.g. toxic epidermal necrolysis (mouth ulcers, rash)
• Hepatic disorders e.g. hepatitis
• Antiepileptic Hypersensitivity Syndrome – symptoms commonly seen are fever, rash, swollen
lymph nodes

Question 4

Major Route of Elimination

Answer 4

Hepatic metabolism

Question 5

Actions Required

Answer 5

• Advise patient to report immediately to a doctor if any warning signs occur
• Ensure the patient receives the same brand of medicine at each time of collecting a prescription
and that the patient is aware of which brand they are maintained on
• Ensure patient is aware of the law regarding seizures and driving
• Inform the patient of potential interactions and the need to check with a pharmacist or doctor
before taking any new medication (including OTC, prescribed or herbal medicines)

Question 6

Interactions

Answer 6

• Increased plasma concentration with acetazolamide, cimetidine, clarithromycin, erythromycin,
fuoxetine, isoniazid
• Decreased plasma concentration with phenytoin, rifabutin, St. John’s Wort
• Carbamazepine reduces plasma concentration of antipsychotics, corticosteroids, coumarins,
eplerenone, oestrogens, progestogens, simvastatin
• Anticonvulsant effect antagonised by mefoquine, antipsychotics
• Possible increased risk of convulsions when antiepileptics given with orlistat