Objective. It has been demonstrated clearly that sweet-tasting solutions given before a painful intervention can reduce pain among newborns. There is no fully accepted explanation for this effect, but activation of endogenous opioids has been suggested as a possible mechanism. The aim of this study was to obtain deeper knowledge of the underlying mechanism by investigating whether administration of an opioid antagonist would reduce the effect of orally administered glucose at heel stick among term newborns.

Design. A randomized, placebo-controlled, double-blind trial with a validated, neonatal, pain-rating scale.

Participants. The trial included 30 term newborns undergoing heel stick, who were assigned randomly to 1 of 2 groups, ie, group I, with naloxone hydrochloride (opioid antagonist) 0.01 mg/kg administered intravenously before oral administration of 1 mL of 30% glucose, or group II, with a corresponding amount of placebo (saline solution) administered intravenously before oral administration of glucose.

Outcome Measures. Pain-related behavior during blood sampling was measured with the Premature Infants Pain Profile. Crying time and heart rate were also recorded.

Results. The 2 groups did not differ significantly in Premature Infant Pain Profile scores during heel stick. The median crying time during the first 3 minutes was 14 seconds (range: 0–174 seconds) for the naloxone group and 105 seconds (range: 0–175 seconds) for the placebo group. There was no significant difference in heart rate between the 2 groups.

Conclusion. Administration of an opioid antagonist did not decrease the analgesic effect of orally administered glucose given before blood sampling.

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