How does Methadone interact with Synthroid ?

My mom is taking 125 micrograms a day [morning] with 10 mg of methadone in the afternoon. On both prescriptions it says it has drug interactions with the other; my question is what exactly is the drug interaction? She does not have insurance so it is very hard to get these 2 docters working together.. thank our health care system!

: http://alcoholdrugstreatment.info/how-does-methadone-interact-with-synthroid