In a study comparing the physiological and subjective effects of heroin and morphine administered intravenously in post-addicts, the post-addicts showed no preference for one or the other of these drugs when administered on a single injection basis. Equipotent doses of these drugs had quite comparable action time courses when administered intravenously, and on this basis there was no difference in their ability to produce feelings of "euphoria," ambition, nervousness, relaxation, drowsiness, or sleepiness.
Although the heroin abstinence syndrome was of shorter duration than that of morphine, the peak intensity was quite comparable for the two drugs. Data acquired during short-term addiction studies did not support the statement that tolerance develops more rapidly to heroin than to morphine. These findings have been discussed in relation to the physiochemical properties of heroin and morphine and the metabolism of heroin. When compared to other opioids — hydromorphone, fentanyl, oxycodone, and meperidine — post-addicts showed a strong preference for heroin and morphine over the others, suggesting that heroin and morphine are more liable to abuse and addiction. Morphine and heroin were also much more likely to produce feelings of euphoria and other such subjective effects when compared to most other opioid analgesics.
W. R. Martin 1 and H. F. Fraser 1
1 National Institute of Mental Health, Addiction Research Center, U. S. Public Health Service Hospital, Lexington, Kentucky
Journal of Pharmacology And Experimental Therapeutics, Vol. 133, Issue 3, 388-399, 1961