Toxic concentration

Serum carbamazepine concentrations are loosely associated with the following clinical features:

• 5 to 12 mg/L (21 to 51 micromol/L)—therapeutic range
• 12 to 20 mg/L (51 to 85 micromol/L)—nystagmus, sedation, ataxia
• 20 to 40 mg/L (85 to 170 micromol/L)—horizontal and vertical nystagmus, progressive sedation
• more than 40 mg/L (170 micromol/L)—respiratory depression, coma, seizures, cardiovascular toxicity.

Carbamazepine-associated intermittent ileus can cause fluctuations in the serum carbamazepine concentration as a consequence of cyclical and erratic drug absorption (see Mechanism of carbamazepine-associated intermittent ileus for the mechanism of carbamazepine-associated intermittent ileus).

Oxcarbazepine serum concentrations are not routinely available and do not inform risk assessment.