A laboratory study of hydromorphone and cyclazocine on smoking behavior in residential polydrug users

Spontaneous reductions in smoking during double-blind buprenorphine detoxification

OBJECTIVE

Evidence suggests a positive association between administration of psychoactive drugs and rates of cigarette smoking. Prevalence of smoking among opioid-dependent individuals, for example, is four times greater than the general population. We recently completed a randomized double-blind trial evaluating outpatient buprenorphine taper for prescription opioid (PO) abusers, which provided a unique opportunity to examine naturalistic changes in smoking among participants who detoxified without resumption of illicit opioid use.

METHOD

Participants received no smoking-cessation services and were not encouraged to alter their smoking in any way. A subset of 10 opioid-dependent smokers, who were randomized to receive the same 4-week buprenorphine taper and successfully completed detoxification, were included in the present study. They provided staff-observed urine specimens thrice-weekly throughout the 12-week trial. Specimens were analyzed on-site via enzyme-multiplied immunoassay for urinary cotinine, a metabolite of nicotine that provides a sensitive biochemical measure of smoking status.

RESULTS

Mean cotinine levels were significantly different across study phases, with significantly lower cotinine levels during taper (1317.5 ng/ml) and post-taper (1015.8 ng/ml) vs. intake (1648.5 ng/ml) phases (p''s<.05). Overall, mean cotinine levels decreased by 38% between intake and end-of-study, reflecting a reduction of approximately eight cigarettes per day.

CONCLUSIONS

These data provide additional evidence that opioids influence smoking and extend prior findings to include primary PO abusers, rigorous double-blind opioid dosing conditions and urinary cotinine. These results also suggest that, while likely insufficient for complete cessation, patients who successfully taper from opioids may also experience concurrent reductions in smoking and thus may be ideal candidates for smoking cessation services.

Make your own cigarettes: toxicant exposure, smoking topography, and subjective effects

BACKGROUND

Despite considerable use of make your own (MYO) cigarettes worldwide and increasing use in the United States, relatively little is known about how these cigarettes are smoked and the resultant toxicant exposure.

METHODS

In a laboratory study, we compared two types of MYO cigarettes-roll your own (RYO) and personal machine made (PMM)-with factory-made (FM) cigarettes in three groups of smokers who exclusively used RYO (n = 34), PMM (n = 23), or FM (n = 20). Within each group, cigarettes were smoked in three conditions: (i) after confirmed overnight tobacco abstinence; (ii) in an intense smoking paradigm; and (iii) without restrictions. All cigarettes were smoked ad lib through a smoking topography unit.

RESULTS

Plasma nicotine significantly increased after cigarettes in all conditions except PMM in the intense smoking paradigm. Puff volume, puff duration, total puff volume, and puff velocity did not differ between cigarette types but the puffs per cigarette and time to smoke were significantly smaller for RYO compared with PMM and FM. Regardless of the cigarette, participants consumed the first three puffs more vigorously than the last three puffs.

CONCLUSIONS

Despite the belief of many of their consumers, smoking MYO cigarettes is not a safe alternative to FM cigarettes. Like FM, MYO cigarettes expose their users to harmful constituents of tobacco smoke. Despite differences in size and design their puffing profiles are remarkably similar.

IMPACT

These data are relevant to health and regulatory considerations on the MYO cigarettes.

Mixed κ/μ partial opioid agonists as potential treatments for cocaine dependence

Cocaine use activates the dopamine reward pathway, leading to the reinforcing effects of dopamine. There is no FDA-approved medication for treating cocaine dependence. Opioid agonists and antagonists have been approved for treating opioid and alcohol dependence. Agonists that activate the μ opioid receptor increase dopamine levels in the nucleus accumbens, while μ receptor antagonists decrease dopamine levels by blocking the effects of endogenous opioid peptides. Activation of the κ opioid receptor decreases dopamine levels and leads to dysphoria. In contrast, inhibition of the κ opioid receptor decreases dopamine levels in the nucleus accumbens. Antagonists acting at the κ receptor reduce stress-mediated behaviors and anxiety. Mixed partial μ/κ agonists have the potential of striking a balance between dopamine levels and attenuating relapse to cocaine. The pharmacological properties of mixed μ/κ opioid receptor agonists will be discussed and results from clinical and preclinical studies will be presented. Results from studies with some of the classical benzomorphans and morphinans will be presented as they lay the foundation for structure-activity relationships. Recent results with other partial opioid agonists, including buprenorphine derivatives and the mixed μ/κ peptide CJ-15,208, will be discussed. The behavioral effects of the mixed μ/κ MCL-741, an aminothiazolomorphinan, in attenuating cocaine-induced locomotor activity will be presented. While not a mixed μ/κ opioid, results obtained with GSK1521498, a μ receptor inverse agonist, will be discussed. Preclinical strategies and successes will lay the groundwork for the further development of mixed μ/κ opioid receptor agonists to treat cocaine dependence.

Alteration of intravenous nicotine self-administration by opioid receptor agonist and antagonists in rats

RATIONALE

The role played by endogenous opioids in mediating the reinforcing properties of nicotine is unclear. As with preclinical studies, clinical trials with naloxone, a prototypic opioid receptor antagonist have yielded equivocal findings with regard to its efficacy in reducing cigarette smoking.

OBJECTIVE

The aim of the present study was to examine the effects of three opioids that exhibit relative selectivity at mu-, kappa- and delta-opioid receptors on nicotine self-administration in male hooded Lister rats.

METHODS

Graded doses (0.3, 1.0, and 3.0 mg/kg IP) of each opioid agonist or antagonist were tested in different groups of rats repeatedly over three consecutive nicotine intravenous nicotine-self administration (0.03 mg/kg/infusion) sessions. The same treatments were tested in parallel groups of rats trained to respond for food reinforcement.

RESULTS

Naloxone was very effective in attenuating the levels of nicotine self-administered across all doses tested. The selective kappa-opioid receptor agonist U50,488, reduced nicotine self-administration in doses of 1 and 3 mg/kg, while the 0.3 mg/kg dose produced a small increase in nicotine intake. Finally, the specific delta-opioid receptor antagonist, naltrindole did not significantly modify nicotine self-administration behaviour. In contrast, all three opioids failed to modify behaviour maintained by food reinforcement.

CONCLUSIONS

These findings suggest endogenous opioids are crucial in mediating the reinforcing effects of nicotine and that the mu-opioid receptor subtype may represent a potential target for selectively reducing nicotine-taking behaviour as part of a pharmacological approach to develop smoking cessation aids.

Endogenous opiates and behavior: 2004

This paper is the 27th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over 30 years of research. It summarizes papers published during 2004 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.