What are the side effects of methadone?

I know methadone is used by a lot of people who are getting themselves treated for their opioid dependence. It can also be used for the treatment of pain. I just want to know what the side effects of methadone are and is this safe to use? Wouldn't the user get addicted to methadone also?

: http://alcoholdrugstreatment.info/what-are-the-side-effects-of-methadone