Despite preclinical evidence supporting the role of the endogenous opioid system in the reinforcing effects of nicotine, the efficacy of the opioid antagonist naltrexone (NTX) as a tobacco dependence treatment remains unresolved. Research is needed to identify those smokers for whom NTX will have the strongest beneficial effects on smoking behavior. The research bridges existing knowledge of genetic, pharmacologic, and behavioral responses to nicotine, and translates this knowledge to treatment for tobacco dependence. The immediate goal was to test whether genetic variation in the mu-opioid receptor gene predicts the effects of naltrexone (NTX) on nicotine reinforcement.
Name: NaltrexoneDescription: All participants took naltrexone during one of the two 4-day study medication periods. Both 4-day study medication periods were randomized and counterbalanced between naltrexone and placebo; all study medication periods were separated by a 5-7 day washout period. Dosing of the naltrexone was the same for all participants: Day 1: 12.5mg, Day 2: 25mg, Days 3 and 4: 50mg.Type: Drug
Name: PlaceboDescription: All participants took a placebo (sugar pill) during one of the two 4-day study medication periods. Both 4-day study medication periods were randomized and counterbalanced between naltrexone and placebo. Placebo capsules matched the naltrexone in color, weight and inactive ingredients. The only difference the lack of active naltrexone in each capsule.Type: Drug
Description: On day 4 of each study medication period, participants completed a cigarette choice procedure where the subject is asked to take 4 puffs from a nicotinized (nicotine-containing) or a denicotinized (no nicotine) cigarette every 30 minutes for 2 hours (maximum of 24 puffs). The outcome variable is the number of nicotine cigarette choices or puffs out of 24 total puffs during these cigarette choice procedures. Subjects who had the A/A genotype took an average of 18.5 puffs from the nicotine-containing cigarettes. Subjects with the A/G or G/G genotypes took an average of 16.2 puffs from the nicotine-containing cigarettes.Measure: Number of Nicotine Cigarette Choices Taken During the Cigarette Choice Procedure. Time: 2 hours
There are 2 SNPs
A key question was whether smokers differ in their responses based on the mu opioid receptor gene (OPRM1) Asn40Asp (A118G) variant. --- Asn40Asp --- --- A118G ---
A key question was whether smokers differ in their responses based on the mu opioid receptor gene (OPRM1) Asn40Asp (A118G) variant. --- Asn40Asp ---