While many people experience side effects from antiepileptic medications, others do not. Common side effects include fatigue, dizziness, weight gain or loss, drowsiness, double or blurry vision, memory loss, thinking impairment or mood swings. Severe side effects include allergic reactions, including rash and difficulty breathing. Other side effects include nausea, slurred speech and bone loss, which can lead to osteoporosis over the long term. Some antiepileptic medication makes hormonal birth control less effective, so be sure to discuss this drug interaction with your health care professional if you use or want to use hormonal contraceptives such as birth control pills, an IUD that releases hormones or long-acting progestin shots or implants.