My grandma has copd, could she take methadone?

Copd. Avoidance of any type of narcotic therapy is typically advised in patients with copd. Narcotics have the potential of making a patients not be able to expire carbon dioxide which could be life threatening. If a patient has been on narcotics for a long time, the chance of this is less, if they are not increasing the dose.
Possibly. Any older person, especially with repsiratory medical issues, should be very careful with any medication that causes sedation and respiratory depression.