Yes it is! I'm on methadone and was just prescriped ciprelax by my methadone doc. Obviously he wouldn't have presciped it if it wasn't safe, so don't worry:)
No one here will probably answer this because we are not Doctors and answering this is too close to giving medical advice. If you are on methadone, I am hoping it is prescribed. Ask your Doctor this question, or at least a pharmacist.