 Morphine and heroin were also much more likely to produce euphoria and other positive subjective effects when compared to these other opioids.The choice of heroin and morphine over other opioids by former drug addicts may also be because heroin (also known as morphine diacetate, diamorphine, or diacetyl morphine) is an ester of morphine and a morphine prodrug, essentially meaning they are identical drugs "in vivo".Heroin is converted to morphine before binding to the opioid receptors in the brain and spinal cord, where morphine causes the subjective effects, which is what the addicted individuals are seeking.