Mandelin Reagent and methadone

[joho]

Can anyone tell me whether methadone is in anyway similar to codeine or heroin such that it will produce a positive colour change reaction when the Mandelin reagent is applied to it?

 

I understand that methadone is an opioid (ie synthetic) rather than an opiate (ie natural compound of opium) but can't seem to find out why this test result should be positive, when methadone is chemically different.

 

Thanks in advance to anyone that can help.