NALORPHINE

Fetal Risk Summary

Nalorphine is a narcotic antagonist that is used to reverse respiratory depression from narcotic overdose. It has been used either alone or in combination with meperidine or morphine during labor to reduce neonatal depression (1,2,3,4,5 and 6). Nalorphine has also been given to the newborn to prevent neonatal asphyxia (3,7). Although some benefits were initially claimed, caution in the use of nalorphine during labor has been advised for the following reasons: (a) a statistically significant reduction in neonatal depression has not been demonstrated; (b) the antagonist reduces analgesia; and (c) the antagonist may increase neonatal depression if an improper narcotic-to–narcotic antagonist ratio is used (8).

An adverse effect on fetal cord blood pH, pCO2, and base deficit was shown when nalorphine was given in combination with meperidine during labor (9). As indicated above, nalorphine may cause respiratory depression in the absence of narcotics or if the critical ratio is exceeded (8). Because of these considerations, the use of nalorphine either alone or in combination therapy in pregnancy should be discouraged. If a narcotic antagonist is indicated, other agents that do not cause respiratory depression, such as naloxone, are preferred.

Breast Feeding Summary

No data are available.

References

1. Cappe BE, Himel SZ, Grossman F. Use of a mixture of morphine and N-allylnormorphine as an analgesic. Am J Obstet Gynecol 1953;66:1231–4.
2. Echenhoff JE, Hoffman GL, Funderburg LW. N-Allylnormorphine: an antagonist to neonatal narcosis produced by sedation of the parturient. Am J Obstet Gynecol 1953;65:1269–75.
3. Echenhoff JE, Funderburg LW. Observations in the use of the opiate antagonists nalorphine and levallorphan. Am J Med Sci 1954;228:546–53.
4. Baker FJ. Pethidine and nalorphine in labor. Anaesthesia 1957;12:282–92.
5. Gordon DWS, Pinker GD. Increased pethidine dosage in obstetrics associated with the use of nalorphine. J Obstet Gynaecol Br Commonw 1958;65:606–11.
6. Bullough J. Use of premixed pethidine and antagonists in obstetrical analgesia with special Reference to cases in which levallorphan was used. Br Med J 1959;2:859–62.
7. Paterson S, Prescott F. Nalorphine in prevention of neonatal asphyxia due to maternal sedation with pethidine. Lancet 1954;1:490–3.
8. Bonica JJ. Principles and Practice of Obstetric Analgesia and Anesthesia. Philadelphia, PA: FA Davis, 1967:254–9.
9. Hounslow D, Wood C, Humphrey M, Chang A. Intrapartum drugs and fetal blood pH and gas status. J Obstet Gynaecol Br Commonw 1973;80:1007–12.