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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: 56-54-2

Chemical structure

Drug Levels and Effects

Summary of Use during Lactation

Limited information indicates that maternal doses of quinidine up to 1.8 grams daily produce low levels in milk and would not be expected to cause any adverse effects in breastfed infants, especially if the infant is older than 2 months. Exclusively breastfed infants should be carefully monitored if this drug is used during lactation, possibly including measurement of serum levels to rule out toxicity if there is a concern.

Drug Levels

Maternal Levels. In one case report, a quinidine milk level of 6.4 mg/L was reported 3 hours after a dose while taking 600 mg every 8 hours orally of a sustained-release quinidine sulfate preparation (Quninidex). In the same patient, a random milk level of 8.2 mg/L was also measured.[1] Data from this case indicate that a breastfed infant would receive about 3 to 4% of the maternal weight-adjusted dosage of quinidine.

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.


Hill LM, Malkasian GD Jr. The use of quinidine sulfate throughout pregnancy. Obstet Gynecol. 1979;54:366-8. [PubMed: 471380]

Substance Identification

Substance Name


CAS Registry Number


Drug Class

Disclaimer: Information presented in this database is not meant as a substitute for professional judgment. You should consult your healthcare provider for breastfeeding advice related to your particular situation. The U.S. government does not warrant or assume any liability or responsibility for the accuracy or completeness of the information on this Site.

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

Bookshelf ID: NBK501089PMID: 30000148


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