Can a single measurement of carbamazepine suffice for therapeutic monitoring?

Using fluorescence polarization immunoassay, we measured the peak and trough concentrations of total and free carbamazepine in serum and saliva from 33 epileptic children. We found that, except for patients who show side effects, measurement of trough values in a single sample, collected after an overnight fast and before the morning dose, sufficiently estimates clinical response. Moreover, total carbamazepine is as informative as free carbamazepine.