Chronic and high dose methadone can lead to serious side effects. Most methadone clinics ignore this as it would cut into profits. Methadone maintenance patients should be on a high quality multivitamin and the recommended high dose of vitamin D. They should also see a endocrinologist at least every six months. IMHO people should stay at or below 40mgpd. Methadone can lead to significant health conditions if taken without doing these things.
Methadone side effects, separating fact and fiction.
Low vitamin d status of patients in methadone maintenance treatment.
Methadone
Neuropathic Pain: Causes, Management and Understanding
Hypogonadism and Low Testosterone Levels as a Side Effect of Methadone and Buprenorphine
Hypogonadism in men receiving methadone and buprenorphine maintenance treatment.
Opioid-Induced Endocrinopathy