Measurement of Amiodarone Levels in the Breast Milk of a Japanese Woman With Peripartum Cardiomyopathy

Abstract

This study aimed to measure the concentrations of amiodarone (AM) and its active metabolite, mono-N-desethylamiodarone (DEA), in the breast milk of postpartum Japanese women treated with AM for ventricular tachycardia associated with peripartum cardiomyopathy and to conduct a follow-up study on the long-term growth and development of infants after resumption of breastfeeding. The patient was a 28-year-old Japanese woman with no underlying diseases who developed ventricular tachycardia and peripartum cardiomyopathy after giving birth. She was administered AM for three days via a combination of oral and intravenous administration. Breastfeeding began 35 days after the end of AM. Breast milk was collected 14 and 39 days after the end of AM, and its concentration in breast milk was measured using high-performance liquid chromatography. Furthermore, the growth and developmental test results of the twins were tracked for three years. Fourteen days after the end of AM administration, the AM concentration in breast milk was 111 ng/mL and the DEA concentration was 143 ng/mL. After 39 days, the AM concentration in breast milk was 11.8 ng/mL, and the DEA concentration in breast milk was 36.6 ng/mL. Studies have reported that pregnant women receiving AM are at risk of causing infant hypothyroidism and developmental delays due to the drug's high iodine content. Given the potential risks of invasive procedures and low milk intake, thyroid function testing was not conducted in the infant. Both twins were noted to be obese but had no clinical complications, and developmental evaluations showed no deficits. It was believed that resuming breastfeeding at that time was appropriate. Considering the risks associated with hypothyroidism, it is necessary to carefully determine the timing of breastfeeding initiation based on factors such as the mother's AM dosage, maternal blood concentration, and the infant's breast milk intake. However, it is considered acceptable for breastfeeding women who have received oral or intravenous AM for several days postpartum to breastfeed their infants.

Keywords: amiodarone; japanese; mono-n-desethyl amiodarone; peripartum cardiomyopathy; transferable into milk.

Figure 1. Chest X-ray of the mother

A: At the time of admission; B: First day after giving birth

Figure 2. Twelve-lead electrocardiogram waveform of the mother

A: At the time of admission; B: Four days after giving birth (when amiodarone treatment ended)

Figure 3. Dosage of amiodarone for the mother after childbirth

The gray band at the top of the diagram indicates the intravenous infusion of amiodarone (AM). On the second day after birth, 150 mg AM was administered intravenously for 10 min (black arrow). Subsequently, 288 mg was administered at a rate of 33 mL/h as a loading dose, and the rate was reduced to a maintenance rate of 17 mL/h; 462 mg was administered for a total of 750 mg, at which point intravenous administration was completed. Arrhythmia recurrence was observed at the end of the third day after birth. AM administration was resumed at a rate of 17 mL/h, and intravenous administration was terminated after 337 mg was administered. The lower part of the figure shows oral administration of AM (white arrow). The mother started taking 100 mg orally once the second night after childbirth and completed four doses at 12-hour intervals.

Figure 4. Pulse rate changes in the mother postpartum

Figure 5. Timeline of medications administered to the mother during the perinatal period

Figure 6. Results of measuring the maternal blood and milk concentrations of AM and DEA

AM: amiodarone, DEA: mono-N-desethylamiodarone