EDROPHONIUM

Fetal Risk Summary

Edrophonium is a short-acting quaternary ammonium chloride with anticholinesterase activity used in the diagnosis of myasthenia gravis. The drug has been used in pregnancy without producing fetal malformations (1,2,3,4,5,6 and 7).

Because it is ionized at physiologic pH, edrophonium would not be expected to cross the placenta in significant amounts. The molecular weight (about 202 for edrophonium chloride) is low enough, however, that placental transfer of the nonionized fraction probably occurs.

Caution has been advised against the use during pregnancy of IV anticholinesterases because they may cause premature labor (1,3). This effect on the pregnant uterus increases near term. IM neostigmine has been recommended as an alternative to IV edrophonium if diagnosis of myasthenia gravis is required in a pregnant patient (3). However, vaginal bleeding and abortion have occurred with IM neostigmine and are potential complications (see Neostigmine). In one report, IV edrophonium was given to a woman in the 2nd trimester in an unsuccessful attempt to treat tachycardia secondary to Wolff-Parkinson-White syndrome (6). No effect on the uterus was mentioned and she continued with an uneventful full-term pregnancy.

Transient muscular weakness has been observed in about 20% of newborns of mothers with myasthenia gravis (8). The neonatal myasthenia is caused by transplacental passage of antiacetylcholine receptor immunoglobulin G antibodies (8).

Breast Feeding Summary

No reports describing the use of edrophonium during lactation have been located. Edrophonium is ionized at physiologic pH and is not expected to be excreted into breast milk (9). The molecular weight (about 202 for edrophonium chloride) is low enough, however, that excretion of the nonionized fraction into milk may occur. The effects, if any, on a nursing infant from this exposure are unknown (9).

References

1. Foldes FF, McNall PG. Myasthenia gravis: a guide for anesthesiologists. Anesthesiology 1962;23:837–72.
2. Plauche WG. Myasthenia gravis in pregnancy. Am J Obstet Gynecol 1964;88:404–9.
3. McNall PG, Jafarnia MR. Management of myasthenia gravis in the obstetrical patient. Am J Obstet Gynecol 1965;92:518–25.
4. Hay DM. Myasthenia gravis in pregnancy. J Obstet Gynaecol Br Commonw 1969;76:323–9.
5. Heinonen OP, Slone D, Shapiro S. Birth Defects and Drugs in Pregnancy. Littleton, MA:Publishing Sciences Group, 1977:345–56.
6. Gleicher N, Meller J, Sandler RZ, Sullum S. Wolff-Parkinson-White syndrome in pregnancy. Obstet Gynecol 1981;58:748–52.
7. Blackhall MI, Buckley GA, Roberts DV, Roberts JB, Thomas BH, Wilson A. Drug-induced neonatal myasthenia. J Obstet Gynaecol Br Commonw 1969;76:157–62.
8. Plauche WC. Myasthenia gravis in pregnancy: an update. Am J Obstet Gynecol 1979;135:691–7.
9. Wilson JT. Pharmacokinetics of drug excretion. In Wilson JT, ed. Drugs in Breast Milk. Balgowlah, Australia:ADIS Press, 1981:17.