10mg of methadone
isn't gonna block anything. Methadone doesn't "block" other opioids
from working; in fact, it's an opioid
agonist in its own right. People on MMT (methadone maintenance) tend to not be able to get high on other opioids because their opiate
receptors are super-saturated with the methadone; methadone attaches more strongly to your brain receptors than many other opioids but isn't quite as euphoric, so when you're well-saturated with methadone & try to shoot up some Heroin
, your brain says "Sorry, Heroin, the receptors are all filled up with methadone right now!"
5, 10, 15mg of methadone isn't gonna block a dose of quality Heroin. Perhaps your buddy who nodded out had taken benzodiazepines
prior to dosing with Heroin? I could still feel a shot of Heroin, right up through to reaching a daily dose of 90mg of methadone. So 10mg shouldn't really block anything.
, which is bupe + naloxone), however, *DOES* block the effects of other opioids. Bupe is both an opiate agonist (gets you high) & an opiate antagonist (blocks your high) in its own right - Subutex (just bupe) will block other opioids just the same as Suboxone (bupe + naloxone aka Narcan), the Narcan in Suboxone is just to prevent IV abuse. Even so, very low doses of buprenorphine (2mg & less) don't fully saturate the opiate receptors, so some of the effects of other strong opioids can often be felt on top. However, one is far more likely to "waste" their money if they've taken bupe & want to shoot Heroin, than if they'd taken methadone & then want to shoot Heroin.
the Heroin you got before couldn't have been that great, because 10mg of methadone shouldn't affect anyone's ability to get high on Heroin after dosing it.
ps. I know you didn't ask about or mention buprenorphine in your post, but I thought I'd throw the information out there just in case.