Reliability of sequential naloxone challenge tests.

To determine the reliability of serial naloxone challenges, five heroin addicts stabilized on methadone were given 0.2 mg naloxone intravenously on three consecutive days. Two-factor ANOVA revealed that the between-subjects effect accounted for at least 63% of the variance in each of the dependent measures, and the effect of challenge number for at most 22%. Withdrawal tended to be slightly more severe for the first challenge. Intraclass correlation coefficients were calculated for the area-under-the-curve of the change from baseline: subject-rated (.74) and observer-rated (.71) withdrawal, pulse (.88), systolic blood pressure (.58), diastolic blood pressure (.85), and skin temperature (.63).