Oh yeah - another thing is that Dilaudid (hydromorphone) is actually more potent than heroin both by weight and by receptor affinity. So if you have even a relatively small tolerance to Dilaudid, you're gonna feel less of a rush from H although still get buzzed. The reason for this is because the D has down-regulated your receptors and if you've taken it relatively recently, will be bound to some of those receptors. When you inject the heroin, it rapidly crosses the blood brain barrier, and gets converted into morphine and 6-mam immediately - both of which are what bind to the recetors. Heroin itself actually has a very weak binding affinity to mu receptors, if at all. So somebody with a whole bunch of healthy and unoccupied mu-opiate receptors scattered all over the brain and spinal cord will very rapidly have a flurry of morphine and heroin metabolites binding to them, leading to the subjective sensation of a rush - nothing more than empty receptors very rapidly being filled then activated. If you have fewer of them because of having tolerance or recently having taken Dillies, there are fewer receptors available either way for morphine and 6-mam to bind to, and so you don't feel as much of an instant gratification.
However, morphine has a long half-life, while Dilaudid has one of the shortest of the conventionally-used opioids. As a result of this, once you do a shot of H, even though you may not feel the immediate rush there will still be a preponderance of morphine molecules circulating through your bloodstream, just waiting to attach to those wonderful mu receptors as hydromorphone is rapidly cleared from them, broken down and excreted. This gradual binding and replacement of morphine gives you that opiate feeling which can last quite a long time until its eventual metabolism as well. Again, even if you haven't got any Dilaudid left in your system, any amount of previous opiate use that is regular will cause a down-regulation of mu- receptors, and so once again there are less of them to be nearly instantly activated by the heroin metabolites to produce the rush.
In summary, if you want the best heroin rush, you need to get the best possible product (preferably others will try it and confirm how good it is) and make sure you have lost most of your tolerance to opiates by waiting at least 3-5 days. If you do this and inject good H, you WILL get an awesome rush. Just make sure you be VERY CAREFUL if you've lost tolerance and then do H because you will need a MUCH LOWER DOSE than usual as a result.
