1 mL EDTA (lavender top) or heparin (green top) plasma. centrifuge sample and separate plasma from cells immediately before the next oral dose (trough). If this is Clearly label tube as EDTA or heparin plasma. Refrigerate.
Note: Ideal sampling time for all antiepileptic drugs is immediately before the next oral dose (trough). If this is not possible, patients should not be advised to delay their scheduled dose for longer than 2-3 hours. Sample collection time and the time that the medication was last ingested should be noted on the requisition.