[Importance of measuring blood level of lamotrigine for optimum dosing schedule]

It is sometime difficult to achieve effective blood levels of lamotrigine (LTG) by the methods of administration presented in the product labeling (PL). We highlighted the importance of measuring LTG blood levels, and proposed a method of adjusting the optimum dosage of LTG based on the pharmacokinetic interaction.

Four types of maintenance dose of LTG were determined whether LTG was administrated in combination with valproate sodium and/or enzyme-inducing antiepileptic drugs or with agents except for them. This method is compared with the method presented in the PL. We exhibited the clinical course of three patients who took LTG according to our method since the blood levels were not elevated enough by the method shown in the PL.

The maintenance dosage described in the PL was lower than that in our methods. The blood levels in these three patients were increased enough to be effective after the therapy by our method.

Measuring the LTG blood level is important to create an optimum dosing schedule. Since the maintenance doses of LTG presented in PL may be inappropriate, they should be adequately adjusted by reference to the LTG blood level.