Therapeutic drug monitoring in epilepsy: an alternative approach

Therapeutic drug monitoring is an important part of antiepileptic therapy, and the search for alternative non-invasive methods of such monitoring represents an actual task for clinical neurology. For this purpose, we determined by gas chromatography and mass spectroscopy the levels of the anticonvulsant carbamazepine in the plasma and saliva of healthy volunteers aged 18–25 years after one oral dose of 200 mg. Maximal drug concentration was 2.6–2.7 µg/ml in the plasma and 0.75 µg/ml in the saliva; mean saliva/plasma drug level ratio was 0.3. Time necessary to reach maximal concentration was 6–7 hrs for both plasma and saliva. T1/2 was also equal for both sources: 15–16 hrs. Significant correlation between the plasma and saliva carbamazepine concentrations was revealed (R2=0,893). Thus, while treating epilepsy patients with carbamazepine, it is possible to use the saliva as an adequate biological sample for conducting non-invasive drug monitoring.