Carbamazepine

General Information

Carbamazpine (Tegratol) is an anticonvulsant drug which is used for the treatment of generalised grand tonic-clonic (grand mal) and patial (focal) seizures. It is also used for the prophylaxis of manic-depressive illness in patients unresponsive to lithium and for the treatment of diabetic nephropathy. Carbamazpine induces its own metabolism and therefore half-life is decreased by chronic administration. Dose may need be increased to maintain effect in the first month of treatment.

Side effects that may be seen at any dose but are related to higher concentrations include:

• Dizziness
• Uncoordinated movement
• Sleepiness
• Blurred or double vision
• Nystagmus
• A red itchy rash
• Nausea
• Diarrhoea
• Constipation
• Confusion

Carbamazepine can also sometimes cause liver function abnormalities, low blood sodium levels, a decrease in white blood cells (WBCs) or an increase in eosinophils (a type of WBC).

As CBZ concentrations can vary quite markedly across the dosage interval, isolated measurements can be difficult to interpret, and standardisation of sample timing is advisable for long term monitoring. Samples should be taken at trough drug levels by collecting a sample prior to the next dose of carbamazepine.