Morphine is considered the best pain relieving drug which the clinician has at his disposal, yet there are elements of tolerance, addiction and gastrointestinal disadvantages to its use. It is common knowledge that the drug often causes undesirable constipation. Further, when morphine is given over long periods of time, tolerance develops, and addiction may be the end result. Treadway1 reports that of a series of 1,276 morphine addicts 325 attributed their original downfall to medical use of this drug. Other authors give conflicting reports, but it is interesting that Adams2 states that in Great Britain all the witnesses called before the Departmental Committee except one considered the medical use of morphine as the immediate exciting cause of addiction in a "considerable proportion of drug habitués." Still another drawback to morphine is the frequent necessity of giving large doses, which more quickly leads to tolerance and addiction.
SLAUGHTER D, PARSONS JC, MUNAL HD. NEW CLINICAL ASPECTS OF THE ANALGESIC ACTION OF MORPHINE. JAMA. 1940;115(24):2058–2060. doi:10.1001/jama.1940.02810500026007