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Preclinical studies have demonstrated that kappa-opioid agonists can attenuate the neurochemical and behavioral effects of cocaine that are related to its reinforcing efficacy, suggesting that kappa-agonists may serve as pharmacotherapies for cocaine dependence. This 8-week inpatient study examined the ability of enadoline, a selective and high-efficacy kappa-agonist, and butorphanol, a mixed agonist with intermediate efficacy at both mu- and kappa-receptors, to reduce the direct pharmacodynamic effects and self-administration of intravenous cocaine in humans (n = 8). Acute doses of intramuscular enadoline (20, 40, and 80 microg/kg), butorphanol (1.5, 3, and 6 mg/70 kg) and placebo were examined separately as pretreatments during each of three test sessions with cocaine in a constrained random order. A cocaine dose-effect session (0, 20, and 40 mg cocaine i.v., 1 h apart) examined direct pharmacodynamic interactions on subjective and physiological indices; self-administration sessions examined choice behavior for cocaine (40 mg i.v. for six trials) versus money 1) in the presence of a sample cocaine dose with money choices presented in ascending value, and 2) in the absence of a sample dose with money choices presented in descending values. Enadoline (80 microg/70 kg) significantly (p0.05) reduced some of the positive subjective effects of cocaine (e.g., ratings of "high"), while butorphanol failed to modify subjective responses. Both agents were safely tolerated in combination with cocaine without adverse physiological responses. Cocaine self-administration was significantly greater across all pretreatment conditions when the sample dose was given and ascending money choices were used. Enadoline and butorphanol failed to modify cocaine self-administration. These data suggest that these kappa-agonists may be safely administered in the presence of cocaine but do not produce significant attenuation of cocaine's direct effects or self-administration under these acute dosing conditions.

To compare the clinical efficacy of different doses of levomethadyl acetate hydrochloride (known as LAAM) in the treatment of opioid dependence.A randomized controlled, double-blind, parallel group, 17-week study.Outpatient facilities at Johns Hopkins University Bayview Medical Center, Baltimore, Md.Opioid-dependent volunteers (N=180) applying to a treatment-research clinic.Thrice-weekly (Monday/Wednesday/Friday) oral LAAM dose conditions of 25/25/35 mg, 50/50/70 mg, and 100/100/140 mg and nonmandatory counseling.Retention in treatment, self-reported heroin use, and opioid-positive urine specimens.Retention was independent of subjects' sex and dose. Self-reported heroin use decreased in a dose-related manner. At final assessment, patients in the high-dose condition reported using heroin 2.5 of 30 days as compared with 4.1 or 6.3 days for patients in the medium-dose and low-dose conditions, respectively (high dose vs low dose, P.05); urinalysis results were similarly dose related. Overall, 20 (34%) of 59 patients in the high-dose condition remained opioid-abstinent for 4 consecutive weeks, as compared with 8 (14%) of 59 in the medium-dose and 7 (11%) of 62 in the low-dose conditions (P.01). Self-report and urinalysis data are consistent with a greater than 90% reduction in illicit opioid use by the high-dose group relative to pretreatment levels.Opioid substitution treatment with LAAM substantially reduces illicit opioid use. The clinical efficacy of LAAM is positively related to dose.

Buprenorphine is an opioid partial agonist being developed for possible use in the treatment of opioid dependence. In a previous study up to 8 mg of buprenorphine administered 20 hr after a daily dose of methadone in methadone-maintained volunteers produced neither agonist-like nor antagonist-like effects. The purpose of this study was to examine the effects of buprenorphine challenges given 2 hr after a daily methadone dose in maintained volunteers. Seven male volunteers maintained on 30 mg of methadone daily underwent pharmacologic challenges two to three times per week. Medication challenges consisted of double-blind i.m. injections of buprenorphine (0.5-8.0 mg), the opioid antagonist naloxone (0.1 and 0.2 mg), the prototypic opioid mu agonist hydromorphone (5 and 10 mg) or saline. Assessments of physiologic measures, volunteers' self-reports and observer ratings of drug effects were collected in a laboratory session for 2 hr after drug administration, and then for 8 additional hr postsession. Results from the laboratory session showed that on subject and observer ratings naloxone produced typical antagonist-like effects, hydromorphone produced mild agonist-like effects and buprenorphine produced antagonist-like effects. Interestingly, buprenorphine's antagonist activity was not directly dose-related; its most prominent antagonist effects occurred at the 1- and 2-mg doses. These results are consistent with buprenorphine's action as a partial mu opioid agonist and demonstrate that antagonist-like effects can occur under some conditions suggesting buprenorphine should have a low abuse liability in methadone-maintained patients.

The extent to which daily caffeine use is associated with a substance dependence syndrome similar to that associated with other psychoactive drugs is unknown. The purpose of this study was to assess volunteers who reported problems with their use of caffeine for evidence suggesting a diagnosis of caffeine dependence based on the generic criteria for substance dependence from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV).Case-series evaluations.An academic research center.Self-identified adults who believed they were psychologically or physically dependent on caffeine.Diagnoses made by a psychiatrist using a structured clinical interview that included a section on caffeine dependence based on genetic criteria for DSM-IV substance dependence.Double-blind caffeine-withdrawal evaluation.Ninety-nine subjects were screened for the study, and 16 were identified as having a diagnosis of caffeine dependence. Median daily caffeine intake was 357 mg, and 19% of subjects consumed less than the national (US) daily average of caffeine. Criteria used for making diagnoses (and rates of their prevalence) were as follows: withdrawal (94%), use continued despite knowledge of a persistent or recurrent physical or psychological problem that is likely to have been caused or exacerbated by caffeine use (94%), persistent desire or unsuccessful efforts to cut down or control use (81%), and tolerance (75%). Eleven subjects underwent the double-blind caffeine-withdrawal evaluation portion of the study, and nine (82%) of the 11 showed objective evidence of caffeine withdrawal, including eight of 11 with functional impairment.These results, together with other experimental evidence, suggest that caffeine exhibits the features of a typical psychoactive substance of dependence. It is valuable to recognize caffeine dependence as a clinical syndrome, since some people feel compelled to continue caffeine use despite desires and recommendations to the contrary.

Pentazocine is a partial mu agonist opioid with one-half to one-sixth the parenteral analgesic potency of morphine. The purpose of this study was to characterize the effects of pentazocine in comparison to naloxone (an opioid antagonist), hydromorphone (an opioid mu agonist) and saline in methadone-dependent volunteers by using the same experimental methods used previously in the study of the opioid analgesics buprenorphine, butorphanol and nalbuphine. In a residential laboratory, five volunteer male opioid abusers, maintained on 30 mg p.o. of methadone daily, underwent pharmacological challenges 2 to 3 times per week. Pharmacological challenges consisted of a double-blind i.m. injection of: pentazocine (dose range 7.5-120 mg), hydromorphone (5 and 10 mg), naloxone (0.1 and 0.2 mg) or saline. Injections were given 20 hr after the last dose of methadone. Measures included physiological indices and self-reports and observer ratings of drug effects. Naloxone and hydromorphone produced characteristic antagonist-like and agonist-like effects, respectively, on subjective, observer and physiological indices. Pentazocine produced primarily antagonist-like effects, with higher doses (= 60 mg) producing significant elevations of visual analog scale ratings of Drug Effects, Bad Effects and Sick; of observer ratings of piloerection, restlessness and adjective scores of opioid withdrawal; as well as increases in blood pressure, heart rate and pupil diameter and decreases in skin temperature. Similar to the previous study of butorphanol, the specific profile of effects produced by pentazocine differed from that produced by naloxone, suggesting non-mu effects may modulate the mu effects of pentazocine.

This study was conducted to determine whether the acute administration of bromocriptine, a dopamine agonist, modulates the acute pharmacologic effects of i.v. cocaine in humans. Eight current users of i.v. cocaine who were not seeking treatment for their cocaine abuse completed the study while they were inpatients on a research unit. Twelve drug conditions were tested in all subjects in randomized order under double-blind, double-dummy conditions and included cocaine (0, 12.5, 25 and 50 mg, i.v.) in combination with bromocriptine (0, 1.2 and 2.5 mg given orally 2 hr before the cocaine injection). Physiologic and subject- and observer-rated responses were measured. Cocaine alone significantly increased pupil diameter, heart rate and blood pressure, and ratings of drug effect, good effects, liking and rush. Bromocriptine alone significantly increased pupil diameter and heart rate, decreased blood pressure and had only minor effects on subjective measures. There were significant cocaine/bromocriptine interactions on diastolic and mean arterial blood pressure, with combinations producing significantly smaller increases compared to cocaine alone, and on heart rate, with combinations producing significantly larger increases compared to cocaine alone. The physiologic and subjective effects of cocaine were not modified by pretreatment with bromocriptine in any other way that might indicate either a therapeutic benefit or a safety concern. However, bromocriptine alone produced undesirable effects (fainting) that should be considered before administration to outpatient cocaine abusers. Any possible therapeutic benefits of acute administration of bromocriptine in cocaine abuse are not likely to be due directly to modulation of the acute effects of cocaine.

Buprenorphine is an opioid agonist-antagonist being evaluated for treatment of opioid dependence. This study characterized the effects of buprenorphine in comparison to naloxone, hydromorphone and saline, in methadone-dependent volunteers. In a residential laboratory, 6 volunteer male opioid abusers maintained on 30 mg of methadone daily underwent pharmacological challenges 2 to 3 times per week. Pharmacological challenges consisted of a double-blind i.m. injection of: buprenorphine (dose range 0.5-8.0 mg), hydromorphone (5 and 10 mg), naloxone (0.1 and 0.2 mg) or saline. Injections were given 20 hr after the last dose of methadone. Measures included physiologic indices, and self-report and observer ratings of drug effects. Naloxone and hydromorphone produced characteristic antagonist-like and agonist-like effects, respectively, on subjective, observer and physiologic indices. None of the doses of buprenorphine were consistently or systematically identified as an opioid agonist or antagonist on any of the measures. Thus buprenorphine produced minimal effects in methadone-dependent patients. The lack of agonist effects suggests buprenorphine has a low abuse potential in methadone-dependent patients. The lack of antagonist effects suggests buprenorphine can be administered safely to subjects dependent on a low dose of methadone. This lack of effect of buprenorphine distinguishes it from other mixed agonist antagonists previously tested, which produced antagonist effects in this procedure.