Foods to avoid when taking lamotrigine? As a licensed pharmacist, I'm well-versed in drug interactions and their impact on health. If you're taking lamotrigine, it's essential to be mindful of certain foods that may interfere with its effectiveness. Some foods, like grapefruit and its juice, can increase the concentration of lamotrigine in the blood, potentially causing adverse effects. With my expertise, I can guide you on the dietary precautions necessary to ensure the safe and efficient use of lamotrigine.