Hi, how long after starting buprenorphine (6 mg a day for the past three days) can you do a line of heroin without experiencing precipitated or normal withdrawal symptoms ?
Hmm, there's a few things I think you need clarified (and maybe
I need clarified

)...which may help you answer your question.....
1. I'm assuming you mean concurrently with bupe? Or JUST stopped within the same day?
2. Ingesting heroin (in any case) will not initiate precipitated withdrawals. (Curiously, why do you assume this?

)
3. (due to 2.) There's basically
no time after starting bupe and dosing heroin which one would experience any sort (precipitated or not) withdrawal.
I think maybe (ask here or) do a little bit more research on what "precipitated withdrawal" actually is. And how, going from a heavy, daily heroin (or any opiate for that matter) addiction straight to managing that addiction with bupe, causes precipitated withdrawal.
Another affecting agent is, if the formula used to manage the addiction is Suboxone/Subutex, is the Naloxone used in the preparation.
As bigjoey said (ever so eloquently

) a few factors/properties to keep in mind;
- Bupe's half-life vs. heroin (or most other opiates) is roughly double (don't quote me on that exact number)
- Bupe's when compared with heroin has a much higher binding affinity to (certain, look them up if you want specific) opiate receptors
Also,
- Bupe is a
partial-agonist, as a posed to heroin which is a
full-agonist
- If it is a Suboxone/Subutex prep. the ratio of bupe to narc is such that to reduce abuse
Ok, I'll stop there otherwise I'll ramble, lol.
Hope this helps.