Course of weight change during naltrexone versus methadone maintenance for opioid-dependent patients

micro-Opiate receptor agonism has been associated with weight gain, whereas micro-antagonists have been associated with weight neutrality, or even weight loss.

This study examined the course of weight changes in opiate-dependent patients over the first 6 months of treatment in methadone (agonist) versus naltrexone (antagonist) maintenance.

A retrospective chart review was conducted on 36 opiate-dependent patients maintained on methadone (n=16) or naltrexone (n=20). OUTCOME MEASURES AND ANALYSES: The primary outcome measure was change in body weight from baseline to 3 months and 6 months into treatment. Analysis of variance was used to compare mean weights between the methadone- and naltrexone-maintained patients. Secondarily, mean percent weight changes from baseline to 3 months and from baseline to 6 months into treatment were compared using Student's t-test.

There was no difference between weight at baseline, 3 months, or 6 months into treatment between the two treatment groups. Furthermore, there was also no difference between the two groups regarding percent weight change from baseline to 3 months or baseline to 6 months. At 3 months, n=16 methadone patients had a mean weight increase of 1.86 percent (standard deviation [SD] = 7.22 percent) when compared with n=20 Behavioral Naltrexone Therapy (BNT) patients with an increase of 4.63 percent (SD = 6.49 percent). At 6 months, n=16 methadone patients had a mean weight increase relative to baseline of 3.67 percent (SD = 9.52percent) when compared with n=20 BNT patients, who demonstrated a mean increase of 6.69 percent (SD = 7.56 percent). No association was found between baseline weight, defined as "low" or "high" relative to group medians, and percent gain within and between treatment groups.

This study did not detect a statistically different course of weight gain between methadone and naltrexone maintenance treatment for opiate-dependent patients.