The 24 hour variation of salivary carbamazepine and carbamazepine-10,11-epoxide concentrations in children with epilepsy.

Variations in carbamazepine (CBZ) and carbamazepine-10,11-epoxide (CBZ-EP) concentrations were measured in saliva over 24 hours in 33 children with complex partial seizures and/or generalized tonic-clonic seizures; all patients received CBZ as monotherapy. CBZ varied between 37-104% and CBZ-EP varied between 26-119%. One venous blood sample was obtained simultaneously with the first saliva sample before the morning dose of CBZ. The free fraction of plasma CBZ was 25.5%. Medication side effects are most likely to appear within 3-4 hours of drug intake; therefore, it is advisable to take another sample in children demonstrating time-related side effects. A controlled release formulation of CBZ should minimize the fluctuations of salivary drug levels of CBZ and CBZ-EP.