Materials and Methods: Seventy opioid-naïve methadone-intoxicated patients with a mean age of 26 ± 9 years were prospectively included in this study and were treated with naloxone. They were then consecutively assigned to A or B groups (including 35 patients each) receiving 100- and 50-mg naltrexone capsules, respectively. The patients were followed for 48 hours in the hospital and re-evaluated by a phone call follow-up after discharge. Finally, they were compared regarding re-development of the toxicity signs and symptoms, a need for re-administration of naloxone, and the final outcome.

Results: Based on the results, only diastolic blood pressure, serum bicarbonate, and base excess were significantly different between the groups. During hospitalization, one patient in group A experienced apnea while none of the patients in group B had such an experience (P > 0.05). In addition, in follow-up evaluations and after the hospital discharge, the mean venous blood gas (VBG) parameters were found to be identical between both groups. Hospitalization period was similar (all P values were greater than 0.05).

Conclusions: In general, 2 different 50- and 100-mg regimens of naltrexone have the same efficacy in preventing the apnea and respiratory depression in methadone-intoxicated opioid-naïve patients. However, the 50-mg dose is the superior regimen recommended in this respect.