It can. You need to contact your prescribing doctor ASAP.
Methadone, like all opiates can cause respiratory suppression. It has an extremely long half life, and because of this, 24-36 hrs after your last dose, half that amount is still in your bloodstream.
Methadone can also cause or worsen heart rhythm problems, specifically prolonged Q-T SYNDROME and can lead to further problems.
What should you do?
Contact YOUR DOCTOR IMMEDIATELY and DO NOT take any more methadone unless and until instructed to do so by your doctor.