Within- and between-person effects of naltrexone on subjective response to alcohol and craving: A daily diary investigation

OBJECTIVE: Naltrexone is an effective treatment for heavy drinking among young adults, and laboratory-based studies have shown that naltrexone dampens the subjective response to alcohol and craving. However, few studies have tested naltrexone’s dynamic, within-person effects on subjective response and craving among young adults in natural drinking environments. METHODS: Using daily diary data from a randomized, placebo-controlled study of naltrexone efficacy in young adults, we examined the between-person effects of treatment condition (i.e., naltrexone vs. placebo) and medication dosage (daily, targeted, daily+targeted) on the subjective response to alcohol and craving on drinking days. Multilevel mediation models predicted subjective response and craving from treatment condition (between-person) and medication dosage (within-person), accounting for drinking levels. All effects were disaggregated within- and between-person. RESULTS: At the between-person level, naltrexone directly blunted intense subjective effects (i.e., “impaired”, “drunk”), and indirectly blunted subjective effects through reduced drinking. Naltrexone was not associated with craving. Between-person effects were not significant after alpha correction, but their effect sizes (bs=.14-.17) exceeded the smallest effect size of interest. At the within-person level, taking 2 (vs. 1) pills was associated with heavier drinking, and taking 1 (vs. 0) pills was associated with lighter drinking, and lighter drinking was associated with a lower subjective response and craving. Treatment condition did not moderate the within-person effects of dosing on outcomes. CONCLUSIONS: The findings suggest that the direct between-person effect of naltrexone was largest on intense subjective responses, blunting feeling “drunk” and “impaired”. Future research using momentary (rather than daily) assessments could confirm and extend these findings.