Here is some info on MDMA. I do not see seizures listed in the adverse events but there are several others to look for:
MDMA users may encounter problems similar to those experienced by amphetamine and cocaine users, including addiction. MDMA damages brain serotonin neurons. Serotonin is thought to play a role in regulating mood, memory, sleep, and appetite. Research indicates heavy MDMA may cause persistent memory problems in humans; however, a 2011 study has reported limited cognitive decline in users of MDMA.1
Psychological effects can include confusion, depression, sleep problems, anxiety, and paranoia, sometimes lasting for weeks after taking the drug. Physical effects can include muscle tension, involuntary teeth-clenching, nausea, blurred vision, faintness, and chills or sweating. Increases in heart rate and blood pressure are a special risk for people with circulatory or heart disease.
Also, there is evidence that people who develop a rash that looks like acne after using MDMA may be risking severe side effects, including liver damage, if they continue to use the drug. Almost 60 percent of people who use Ecstasy report withdrawal symptoms, including fatigue, loss of appetite, depressed feelings, and trouble concentrating.
MDMA-related fatalities at raves have been reported. The stimulant effects of the drug, which enable the user to dance for extended periods, combined with the hot, crowded conditions usually found at raves can lead to dehydration, hyperthermia (dangerous increase in body temperature), and heart or kidney failure.