Hi,
Can someone explain this clearly to me as I've asked a number of people and got a whole host of different answers....
People talk of subutex being a blocker at optimum doses- i.e. 16mg and above- where anybody using heroin on top will not get an effect from it.
Similarly, people prescibed certain doses of methadone are described as having their opiate receptors saturated and can get no effect from heroin if they use on top.
Can someone describe the difference between saturation and a blocker?

Thanks,
Rich Carroll

Hi Rich,
I guess it means pretty much the same in my mind. You could saturate the receptors with Methadone also just the same was as with Buprenorphine.
You will notice that people on higher doses of Methadone report that Heroin has less effect. They might say things like 'The gear is sh1t' or something similar. I think it would take a large dose of Methadone to block all effects of Heroin.
There is a study with PET scan pictures I'll see if I can look it up and post for you.

From Susi Harris via Blackberry..."This is a very good question which deserves to be asked more often. The proper person to answer it is a pharmacist, however I will have a go at the simplistic medical explanation (pharmacists, please correct all errors..): Firstly you need to understand that when a drug binds to a receptor in your body it is not a permanent state or a fixed end-point, the drug molecule can also unbind. What it does at any given point depends on a balance of several factors: the affinity between drug and receptor, the concentration of drug in the bloodstream, and the presence of other molecules which compete for the same site. In fact molecule and receptor are in a constant state of flux, binding and unbinding (you may think teenage relationships follow similar principles). In the case of methadone, the affinity for opiate receptors is pretty similar to heroin, so given similar concentrations the receptor would be constantly alternating between heroin and methadone. However at very high methadone concentrations, the majority of receptors would bind with methadone, simply because the number of molecules would be overwhelmingly larger than the number of heroin molecules. This is known as saturation. Subutex (buprenorphine) however has a much higher affinity than heroin, so in any competitive situation between the two, buprenorphine would "win" and bind to the opiate receptor in preference to the heroin. Once there is enough buprenorphine for all the opiate receptors in the body to have one, (which seems to be achieved somewhere between 12 and 32 mg, depending on the individual) no heroin molecules will get a look-in. This is known as blocking. Hope this helps"

Hi Rich,
Its always hard to understand once people start talking about receptors and transmitters and things, but I think Susi has drawn a very clear picture.. and written on a blackberry while on holiday! there's dedication to the field. I hope she also gets some ice cream .

That's right, as far as my GP level understanding of neuroscience goes.. as Susi says, the buprenorphine (subutex) molecules latch on to the same sites in the brain which the heroin would normally trigger, but has a stronger affinity and a greater ability to hang on, so that when each of the sites is full, there is no room for the heroin to get in to trigger that heroin feeling.

As long as you get enough of the buprenorphine in to cover all the receptors, the heroin is "blocked" and cannot get in for at least 24-36 hours.

The situation with methadone is more like filling your stomach with ice cream.. if the methadone gets in there first, the stomach gets full,("saturated") and you can if you like pour a bit of heroin in on top, but it won't have much effect, and you are at risk of getting overfull and being sick all over the pavement (if eating ice cream in Brighton) or of
"going over" if taking heroin on top of methadone.

This message has been edited. Last edited by: judith yates,

Thanks, the last two posts were very helpful...

quote:

Originally posted by Rich C:
Thanks, the last two posts were very helpful...

Well thanks very much :-) Rich Inotice you are fairly local to us, if you want to come and visit you are more than welcome.

Sorry dude! I Just needed a scientific/ medical explanation as it's baffled me for ages. Basically, saturation and blocker are the same thing!

You need to buy Karch's Pathology of drug abuse. A good pool-side read and it gives everything about anything to do with drugs in minute detail.

aah Rich, I have just seen your last comment.. and I don't think "saturation" and "blocker" are quite the same. Hopefully if you read susi's explanation again it may become clear. I think her description is really rather good.

Saturation means all the opiate receptors are full, because there's lots of methadone in your brain, but it is a very fluid situation, as Susi points out, and heroin can still get in and have some effect.

The term "blocker" is not quite the same, and suggests a chemical which binds on to the opiate receptor in a much stronger way.. in the case of "full blockers" like naltrexone, and naloxone, this stops all opiate like effect (and can of course save lives in overdose)

In the case of buprenorphine, there is both a blocking effect and also an opiate-like euphoric/analgesic type effect (they refer to it as an agonist/antagonist effect , because luckily it does both) Maybe we do need a pharmacist!

No, I did understand it. it was an excellent explanation. I shouldn't have said they were the same thing- rather, a similar thing.

Hi
As a Pharmacist, I would go with Susi's explanation... because if I were to give you a Pharmacological answer then I think you would die of boredom..... (I am pretty sure you dont want to know about agonists and antagonists!!), and the answer pretty much explains it

I really liked the ice cream analogy!

We are focussing here too much on the chemical effects of a drug and too little on the behavioural and social aspects. Ask any smoker about the beneficial effects of lighting up a fag, even if there is very little time to inhale. Look at how behaviour when drunk is determined by the social setting of the alcohol ingestion.
Blockers (subutex not naltrexone) do not stop heroin use, but they may support other changes which can lead to abstinence