Lamotrigine does not cause weight gain, but in rare cases, it can cause weight loss. The medication is used to control seizures, as stated by WebMD.
Lamotrigine can also be used to control the mood swings associated with bipolar disorder. It does this by balancing certain chemicals in the brain. Some common side effects of Lamotrigine include blurred vision, poor vision or drowsiness, according to Drugs.com. Rare side effects include muscle cramps, dark spots on the skin and sores or ulcers inside the mouth. The medication is available with a prescription and the dosage will vary depending on the condition being treated.