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Drugs and Lactation Database (LactMed®) [Internet]. Bethesda (MD): National Institute of Child Health and Human Development; 2006-.

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Drugs and Lactation Database (LactMed®) [Internet].

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Last Revision: January 7, 2019.

Estimated reading time: 1 minute

CASRN: 51-06-9

Chemical structure

Drug Levels and Effects

Summary of Use during Lactation

Maternal doses of procainamide 2 grams daily produced low levels of the drug and its active metabolite in the milk of one mother. Although it would not be expected to cause adverse effects in older breastfed infants, the relative lack of data concerning breastfeeding during maternal procainamide therapy would argue for careful monitoring if this drug is used while breastfeeding a neonate possibly Measurement of infant serum levels could help to rule out toxicity if there is a concern.

Drug Levels

Maternal Levels. One mother was taking a dose of 500 mg 4 times daily (dosage form not stated, but probably immediate-release). Milk procainamide and N-acetyl procainamide (NAPA) levels were measured on one of the first postpartum days. Procainamide levels averaged 5.4 mg/L (range 2.6 to 10.2 mg/L), and NAPA averaged 3.5 mg/L (range 3.1 to 5 mg/L). Because the mother's serum levels were consistently below the therapeutic range, usual milk levels would probably be higher than reported here. There was no clear correlation between time after the dose and milk levels.[1] Based on data in this case, the average expected dose of procainamide plus NAPA that an infant would receive in breastmilk is less than 5% and the maximum would be less than 7% of the mother's weight-adjusted dosage.

Infant Levels. Relevant published information was not found as of the revision date.

Effects in Breastfed Infants

Relevant published information was not found as of the revision date.

Effects on Lactation and Breastmilk

Relevant published information was not found as of the revision date.


Pittard WB III, Glazier H. Procainamide excretion in human milk. J Pediatr. 1983;102:631-3. [PubMed: 6187910]

Substance Identification

Substance Name


CAS Registry Number


Drug Class

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Attribution Statement: LactMed is a registered trademark of the U.S. Department of Health and Human Services.

Bookshelf ID: NBK501078PMID: 30000137


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