Physiologic, subjective, and behavioral effects of amphetamine, methamphetamine, ephedrine, phenmetrazine, and methylphenidate in manFive centrally acting sympathomimetic amines, d-amphetamine, d-methamphetamine, ephedrine, phenmetrazine, and methylphenidate, were studied in man. All of these agents increased blood pressure and respiratory rate, produced similar types of subiective changes, and increased the excretion of epinephrine. With regard to these parameters, there was a high concordance between estimates of their relative potencies.The concordance between the potency estimates for the different parameters suggests, but does not prove, that these five agents share a common mode of central action. Further, if the peripheral modes of action as elucidated by animal studies are true for man, this study suggests that it is unlikely that their central actions in man are a consequence of the release of norepinephrine in the brain.

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In all, 19 research subjects, with current histories of frequent cocaine use, were exposed to cocaine-related cues to elicit drug craving. We measured the change of occupancy of dopamine at D2-like receptors with positron emission tomography (PET) and inferred a change of intrasynaptic dopamine (endogenous dopamine release), based on the displacement of radiotracer [11 C]raclopride. Receptor occupancy by dopamine increased significantly in putamen of participants who reported cue-elicited craving compared to those who did not. Further, the intensity of craving was positively correlated with the increase in dopamine receptor occupancy in the putamen. These results provide direct evidence that occupancy of dopamine receptors in human dorsal striatum increased in proportion to subjective craving, presumably because of increased release of intrasynaptic dopamine.

The efficacy of buprenorphine and methadone was compared in the outpatient detoxification of heroin addicts. Forty-five patients were randomized to receive either sublingual buprenorphine or oral methadone under double-dummy and double-blind conditions to study the pharmacology of buprenorphine in a 90-day detoxification protocol. The patients were administered either 2 mg buprenorphine or 30 mg methadone for 3 weeks followed by 4 weeks of dose reductions and 6 weeks of placebo medication. No significant between-group differences were seen on measures of treatment retention, drug use, or symptom report. During the hydromorphone challenge, methadone attenuated opioid effects to a greater extent than did buprenorphine on both physiologic (pupil constriction) and self-report measures. However, this did not result in greater abuse of illicit opioid drugs by subjects taking buprenorphine. The results of this clinical trial indicated that buprenorphine was acceptable to patients and as effective as methadone in the detoxification treatment of heroin addicts.

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Modafinil is a unique wake-promoting agent. Preclinical studies indicate a mechanism of action which is distinct from that of amphetamine or methylphenidate. To compare the pharmacodynamic profiles of modafinil, methylphenidate, and placebo in humans, a double-blind Latin square crossover study was conducted in 24 male volunteers with a history of polysubstance abuse that included the stimulant cocaine. Each subject was given single oral doses of methylphenidate (45 mg or 90 mg), modafinil (200 mg, 400 mg or 800 mg) and placebo. Measures of subjective, behavioural, and physiological responses were evaluated at fixed intervals during 72 h after each dosing occasion. Subjects discriminated both modafinil and methylphenidate from placebo. Subjects liked the effects of both drugs. However, modafinil differed from methylphenidate in its lack of a significant response on the Amphetamine Scale of the Addiction Research Center Inventory. The profile of physiological effects for modafinil differed from methylphenidate in that it showed greater inhibition of observed and reported sleep, less facilitation of orthostatic tachycardia and less reduction of caloric intake. These findings are consistent with preclinical pharmacological data suggesting that modafinil is not an amphetamine-like agent.

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