^^^^I agree.
Trinity what are you talking about! I have ived many different formulations of morphine (from ms contin to ampules) hundreds of times, and morphine has a very distinct, and very WARM IV rush, almost too warm. When you inject it, you feel the drug spread throughout your body, limb by limb, you feel the warmth spread. Sometimes with huge doses, my face, arms and chest turn bright red and splotchy, i get that flushing feeling, and i just feel very hot. Even with instant release oral solution, morphine evokes a warm feeling. This happens with heroin to a lesser extent, as heroin is a product of morphine and shares many of its characteristics, especially tar, which has some unreacted morphine in it, and alot of 6-monoacetylmorphine (sometimes it doesnt have any DAM whatsoever).
If i were to say any IV opiate was warm, it would be high dose morphine. I have injected virtually ever conventional (and some unconventional) opiate/opioid that you can think of, and many that you cannot. And from all these injections, ive found morphine has one of the warmest rush. And as i mentioned, even instant release morphine oral solutions creates a sense of warmth. This is somewhat a product of an allergic histamine reaction, but everyone responds differently to this allergic reaction, and some are more prone to it than others. It generally doesnt happen with therapeutical or "medicinal" doses, but it definately happens with LARGE IV doses. Fentanyl, in high doses can give a false sense of warmth and profuse sweating, while infact your body temperature is dropping.
So while it is somewhat subjective, everyone has an allergic histamine reaction to morphine, just some more than others. Perhaps you are the others, or you simply havent injected a large enough dose. But in general, for the VAST majority of people, morphine provides a WARM rush when injected.
If you want an example of a cool refreshing rush, oxycodone IV'ed is a good example. Its a very smooth cool rush, and doesnt cause the histamine reactions like morphine tends to do, but still can produce a sensation of warth in some individuals....