Is it safe to mix methadone with codeine?

Methadone is synthetic and quite harmful and highly addictive.

Codeine and morphine are both natural - made from poppy extract. Of course, cyanide is also natural. 'Natural' does not mean 'safe'.

Morphine is 10 times stronger than codeine.

Morphine and methadone are highly addictive, while codeine only moderately.