CLINICAL SIGNIFICANCE OF A DRUG INTERACTION BETWEEN LAMOTRIGINE AND CYCLIC HORMONAL COMBINATION CONTRACEPTIVE USE IN SELECTED WOMEN WITH SEIZURES: ONE EPILEPSY CENTER[apos]S CLINICAL EXPERIENCE
Abstract number :
2.298
Submission category :
Year :
2005
Submission ID :
5604
Source :
www.aesnet.org
Presentation date :
12/3/2005 12:00:00 AM
Published date :
Dec 2, 2005, 06:00 AM
Authors :
Colleen Vanderkolk, Julie Dagam, George Morris, and Jennifer Burgos
A potential interaction exists between lamotrigine and hormonal combination contraceptives, including oral combination contraceptives. Patients on lamotrigine and hormonal combination contraceptives may experience decreased lamotrigine blood levels and clinical signs including seizures or side effects.
Most hormonal combination contraceptives provide hormones for 21 of each 28 days. Patients taking lamotrigine and cyclic hormonal combination contraceptives, then, may experience a monthly fluctuation in the interaction resulting in fluctuation of lamotrigine blood levels and clinical signs because the patient takes lamotrigine daily but takes active hormones for only 21 of each 28 day cycle.
As a result, we decided to examine our center[apos]s experience with the potential interaction between lamotrigine and cyclic hormonal combination contraceptives, and to characterize the potential clinical significance of this in our patient population. Our center developed data collection forms to identify patients taking lamotrigine and cyclic hormonal combination contraceptives and to record blood levels and clinical changes. In Feb 2005, charts of all female patients were reviewed and those taking lamotrigine were identified.
Identified patients were contacted in March 2005 and ongoing. Current medications were verified and patients on both lamotrigine and cyclic oral contraceptives were scheduled for two lamotrigine blood levels: mid-cycle (after active oral contraceptives for 14 days) and end-of-cycle (after no active oral contraceptives for 7 days).
Patients will be contacted mid-cycle and end-of-cycle for clinical data including changes in seizure frequency and side effects. Clinical data will be compared to blood levels changes. To date, 7 patients agreed to lamotrigine blood levels. By May 2005, end-of-cycle levels are available for 43% (3/7) of patients and 67% (2/3) levels are within the reported reference range while 33% (1/3) is below the reported reference range. Mid-cycle levels are available for 14% (1/7) of patients, and is below the reported reference range. Clinical data is available for one patient, who reported no change in seizure frequency or side effects. All patients were maintained on individualized regimens of antiepileptic medications. Because patients taking hormonal combination contraceptives and lamotrigine may experience a decrease in their lamotrigine blood level, the end-of-cycle level would be expected to be higher than the mid-cycle level. One of three available end-of-cycle levels is unexpectedly below the reference range, but that patient[apos]s mid-cycle level and clinical data are needed for comparison. Data collection is ongoing and our center is continuing to examine our experience and characterize the clinical significance of the interaction in our patient population.