When is it safe to take Demerol after taking 50mg of methadone?

I wouldn't say it's safe because you are talking about very powerful opiates here, but I dont know why you would take Demerol after you took 50mg of MEthadone because it will not really have any effect. Methadone has opiod inhibiting properties and will clog the receptors in your brain, therefore making the Demerol completely useless for the most part.