Summary of Use during Lactation

Because of the low levels of vonoprazan in breastmilk, amounts ingested by the infant are small and would not be expected to cause any adverse effects in breastfed infants. No special precautions are required.

Drug Levels

Maternal Levels. Concentrations of vonoprazan were measured in breastmilk from 15 healthy lactating women following administration of vonoprazan 20 mg once daily (n = 5) or twice daily (n = 10) for 4 days. With the 20 mg vonoprazan once daily regimen, an average peak milk concentration of 20.9 mcg/L occurred at 1.9 hours after the dose and the average concentration of vonoprazan in breastmilk was 7.55 mcg/L. The estimated mean daily infant dose was 0.4 mg/kg, representing 0.128% of the maternal weight-adjusted dose or RID. With the 20 mg twice daily dosage regimen, an average peak milk concentration of 24.7 mcg/L occurred at 1.9 hours after the dose and the average concentration of vonoprazan in breastmilk was 13.3 mcg/L. The estimated average total amount of vonoprazan present in breastmilk over 24 hours was 9 mcg. The estimated mean daily infant dose was 1.5 mcg/kg, representing 0.269% of the maternal weight-adjusted dosage or RID.[1,2]

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

Effects in Breastfed Infants

A woman with peripartum cardiomyopathy and severe nonsustained ventricular tachycardia gave birth to twins. Vonoprazan 10 mg daily as well as amiodarone, bisoprolol, edoxaban, febuxostat, imidapril, and pitavastatin were started postpartum. Breastfeeding began 39 days after birth when the daily intake of breastmilk was 160 mL for the first infant and 120 mL for the second, smaller infant. Breastmilk was mixed with infant formula and accounted for approximately one-quarter of their total daily milk intake. The mother breastfed in infants for approximately two months after starting breastfeeding and the infants had no bleeding tendency. At 3 years of age, both infants had a tendency toward obesity, but no other complications or developmental delay.[3]

Effects on Lactation and Breastmilk

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

Alternate Drugs to Consider

Omeprazole, Pantoprazole

References

1.

Phathom Pharmaceuticals Inc. A study to evaluate vonoprazan concentrations in breast milk of healthy lactating women receiving vonoprazan 20 mg once daily or vonoprazan 20 mg twice daily. clinicaltrials 2025https://clinicaltrials.gov/study/NCT06391177?intr=Vonoprazan&rank=3&tab=results

2.

Mulford D, Brimhall D, Chang YM, et al. A Phase 1, open-label study to evaluate vonoprazan concentrations in breast milk of healthy lactating women receiving vonoprazan 20 mg once daily or vonoprazan 20 mg twice daily. Gastroenterology 2026;170 (6 Suppl):S2602–S3. doi:10.1016/S0016-5085(26)06160-3 [CrossRef]

3.

Watanabe C, Wachi T, Kamada S, et al. Measurement of amiodarone levels in the breast milk of a Japanese woman with peripartum cardiomyopathy. Cureus 2025;17:e89301. [PMC free article: PMC12404898] [PubMed: 40909045]

Substance Name

Vonoprazan

CAS Registry Number

881681-00-1

Drug Class

Breast Feeding

Lactation

Milk, Human

Anti-Ulcer Agents

Gastrointestinal Agents

Proton Pump Inhibitors