If a medicine is making you feel sick and terrible and making you have suicidal thoughts, it's probably best to stop taking it and call the doctor right away. Seroquel doesn't work for everyone and this is why...
When I went to the clinic (on methadone 4 years) there were people on both methadone and seraquel. So mixing them is ok for people that are prescribed it. But as kendrika said talk to your doctor forsure! And please tell us why are you on methadone? What dose? Did you start taking them together? Do you still take them together?
Maybe best to talk to a Dr. I think that mixing them isn't good. You can call any 24 hour Walgreens or pharmacy and talk to a pharmacist about interactions, confidential.