Is Metformin Safe in Breastfeeding

I am a breastfeeding mother and i want to know if it is safe to use Metformin? Is Metformin safe for nursing mother and child? Does Metformin extracts into breast milk? Does Metformin has any long term or short term side effects on infants? Can Metformin influence milk supply or can Metformin decrease milk supply in lactating mothers?

Oral antidiabetic medication used for treatment of Diabetes Type II, Obesity and Polycystic Ovarian Syndrome (PCOS). Biguanide drugs act by decreasing Neoglycogenesis (new formation of sugar) in the liver. Low risk of Hypoglycemia. Metformin is excreted into breast milk in non-significant amount and without harmful effect on breastfed infants of treated mothers, Obesity is associated with breastfeeding difficulties. In spite of Metformin has beneficial effect on Obesity, this is not true with PCOS because lactation capacity is related to growth of breast tissue during pregnancy which is not improved by the use of Metformin, Oral antidiabetic drugs are not effective for Diabetes Type I. For Diabetes Type II diet, physical exercise and breastfeeding may ameliorate glycemia levels. See remarks on mother's Diabetes Mellitus by consulting specific item.

Data from well-conducted studies indicate that metformin levels in milk are low and infants would receive less than 0.5% of their mother's weight-adjusted dosage. Milk metformin levels are relatively constant during maternal metformin use, so timing of breastfeeding with respect to the administration times is of little benefit. Although the dose in milk is low, metformin is sometimes detectable in low levels in the serum of breastfed infants. One sizeable prospective study found no adverse effects in breastfed infants. Metformin should be used with caution while nursing newborn and premature infants and those with renal impairment.

Seven infants aged 5 to 25 months whose mothers were taking metformin (start date and duration not stated) were judged to be healthy with growth and development progressing as expected. Two of the infants also had normal Denver Developmental Screening tests.[1] Three infants aged 2, 5 and 14 months whose mothers were taking metformin 500 mg twice daily had no detectable adverse effects from metformin.[3] In 3 breastfed (extent not stated) infants aged 10 to 11 days postpartum whose mothers were taking an average metformin dosage of 9.6 mg/kg (range 7.5 to 12.4 mg/kg) daily, none of the infants had low blood glucose levels. Their mothers reported no adverse reactions in the infants.[4] Ninety-two mothers of 111 infants were treated with metformin in a mean dosage of 2.2 grams daily (range 1.5 to 2.55 mg daily) throughout pregnancy and postpartum. A 6-month, nonrandomized, prospective trial followed 61 predominantly breastfed and 50 formula-fed infants of these women. No differences in 3- and 6-month outcomes were found by blinded observers between the 2 groups of infants in height, weight, motor-social development or rates of illness.[6][7]

In a study of 250 women who received metformin 500 mg to 2 grams daily in either the immediate- or extended-release formulation for polycystic ovary syndrome, information on breastfeeding was available on 164 women. Of these, 97 (59%) were successful at breastfeeding, 27 (17%) failed, and 40 (27%) made no attempt to breastfeed. Of the 124 who attempted to breastfeed, 78% were successful. Failures were attributed to poor milk production in 4 women, demands of multiple births, infant prematurity, cleft palate and mastitis.[8] In a follow-up to a placebo-controlled study on metformin use during pregnancy in women with polycystic ovary syndrome, women were asked about the duration and extent of breastfeeding. No difference in breastfeeding in the duration of exclusive or partial breastfeeding was observed between the women who received metformin during pregnancy and those who received placebo.[9]