Drug Levels and Effects:

Summary of Use during Lactation:

Because of the low levels of pyridostigmine in breastmilk, amounts ingested by the infant are small and infant serum levels are very low. Pyridostigmine is not be expected to cause any adverse effects in breastfed infants. Most mothers with myasthenia gravis are able to nurse successfully with pyridostigmine treatment, but occasionally breastfeeding must be discontinued to avoid excessive fatigue in the mother.

Drug Levels:

Maternal Levels.

A woman was taking pyridostigmine 120mgevery 4 to5hours for myasthenia gravis during pregnancy. After delivery, she had an undetectable (<100 mcg/L) pyridostigmine level in breastmilk 120 minutes after a 60mgoral dose.[1]

A mother who was taking pyridostigmine 60mg3 times daily (3mg/kg daily) had milk pyridostigmine levels ranging from 13 to 24 mcg/L at various times during the 8-hour dosage interval at5and 35 days postpartum. At 102 days postpartum while taking 40mgtwice daily (2mg/kg daily), milk pyridostigmine levels ranged from the limit of detection (2 to5mcg/L) to5mcg/L during a dosage interval. The time of the peak milk level was about 4 hours after a dose. Another mother who was taking pyridostigmine 60mg5times daily (</span>5mg/kg daily) had milk pyridostigmine levels of 25 and 22 mcg/L at the time of a dose and 2.5hours after a dose, respectively, at 60 days postpartum. The authors estimated that an exclusively breastfed infant would receive a maximum of 0.1% of the maternal weight-adjusted dosage.

Infant Levels.

In an exclusively breastfed 60-day-old infant whose mother was taking pyridostigmine 60mg5times daily (</span>5mg/kg daily), the drug was not detectable in serum (<2 mcg/L) at the time of a dose or 2.6 hours later.[2]

Effects in Breastfed Infants:

A woman was taking pyridostigmine 120mgevery 4 to5hours for myasthenia gravis. Her breastfed (extent not stated) infant reportedly thrived and had no cholinergic side effects.[1]

Two infants whose mothers were taking pyridostigmine 3 and5mg/kg daily during pregnancy and lactation were exclusively breastfed. Both infants gained weight and developed normally and had no signs of cholinergic side effects.[2]

Possible Effects on Lactation:

Relevant published information in nursing mothers was not found as of the revision date. In animals, cholinergic drugs increase oxytocin release,[3] and have variable effects on serum prolactin.[4] The prolactin level in a mother with established lactation may not affect her ability to breastfeed.

In a case series of 69 pregnancies in 65 women with myasthenia gravis over 27 years, 49 patients received pyridostigmine during pregnancy and lactation. Lactation data were available for 33 patients, and 25 of them nursed successfully, although the number of these mothers who were taking pyridostigmine was not given. Nursing was sometimes disrupted to avoid exhaustion in the mother.[5]

Alternate Drugs to Consider:



1. Skoglund RR, Roberts CC, Huddlestone J. The role of anti-acetylcholine receptor antibody in neonatal myasthenia gravis. Bull Los Angeles Neurol Soc. 1978;43:66-9. PMID:757366
2. Hardell LI, Lindstrom B, Lonnerholm G, Olofosterman P. Pyridostigmine in human breast milk. Br J Clin Pharmacol. 1982;14:565-7. PMID:7138742
3. Clarke G, Fall CH, Lincoln DW, Merrick LP. Effects of cholinoceptor antagonists on the suckling-induced and experimentally evoked release of oxytocin. Br J Pharmacol. 1978;63:519-27. PMID:566601
4. Muller EE, Locatelli V, Cella S et al. Prolactin-lowering and -releasing drugs: mechanisms of action and therapeutic applications. Drugs. 1983;25:399-432. PMID:6133737
5. Djelmis J, Sostarko M, Mayer D, Ivanisevic M. Myasthenia gravis in pregnancy: report on 69 cases. Eur J Obstet Gynecol Reprod Biol. 2002;104:21-5. PMID:12128277

Substance Identification:

Substance Name:


CAS Registry Number:


Drug Class:

  • Cholinesterase Inhibitors

  • Parasympathomimetics

  • Administrative Information:

    LactMed Record Number:


    Last Revision Date:

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