^†Codeine addiction is so rare that medical literature contains little information about abuse of the drug. In fact, as late as the mid-1970s, medical literature suggested that codeine addiction was virtually nonexistent and the drug posed little potential for abuse because of its unpleasant side effects, not the least of which was severe constipation. As one study noted, codeine “lacks the ‘thrill’-producing capacity of heroin and morphine. Codeine does not appeal to addicts of the underworld and is of practically no value in the illicit drug market. Moreover, codeine is not especially suitable for intravenous administration, the route preferred by American addicts: Intravenous injections produce effects such as intense erythema, edema, headache, even severe hypotension or vascular collapse, so that the overall sensation is at least unpleasant. Addicts found intravenous codeine unacceptable as a substitute for morphine in a study at the Addiction Research Center in Lexington, Kentucky…. With a few exceptions… pharmacology textbooks usually state that primary codeine dependence is rare among addicts as well as in clinical practice.” As he had done in the movies and in aviation, Hughes rewrote the medical record books on codeine abuse, pioneering a new addiction.