Naltrexone plasma levels, clinical response and effect on weight in autistic children.

This research measured naltrexone levels in plasma, to assess the relationship between behavioral response to naltrexone and plasma levels, and the effects of naltrexone on weight in hospitalized autistic children (n = 41). A double-blind, placebo-controlled, parallel groups design with fixed dose was used, with random assignment to naltrexone or placebo. Drug plasma levels were analyzed by gas chromatography/mass spectrometry, and weights were obtained weekly. Naltrexone levels measured in 17 children ranged from 0.12 to 5.60 ng/mL (mean = 0.71, standard error of the mean = 0.32). There was no relationship between plasma levels and age, level of intellectual functioning, scores on the 14 selected Children's Psychiatric Rating Scale (CPRS) items, Clinical Global Impressions, Global Clinical Consensus, and the CPRS hyperactivity factor. There was a trend (p = .06) for children receiving naltrexone in the highest weight percentile (> or = 90th) to lose weight (mean = -0.42 kg) but this was not the case for those in the lower weight percentiles (mean = +0.03 kg).