Millions rely on prescription medications daily, often without concern. However, during pregnancy or breastfeeding, even common drugs like metformin may come under scrutiny due to concerns about infant safety. This article examines the safety of metformin use while breastfeeding, drawing upon available research and expert opinions.
What is Metformin?
Metformin, known by the brand name Glucophage XR, is an oral medication primarily used to manage Type 2 diabetes. Primary care provider and women’s health expert Navya Mysore, MD, explains that metformin improves insulin sensitivity, decreases glucose production in the liver (hepatic glucose production), and enhances glucose uptake by the body’s cells. It belongs to a class of drugs called biguanides, which reduce glucose absorption from food in the intestines, decrease glucose production in the liver, and increase the body’s sensitivity to insulin. It is the most commonly prescribed antidiabetic agent for Type 2 diabetes mellitus because it effectively reduces the progression of Type 2 diabetes.
Is Metformin Safe During Breastfeeding?
Generally, metformin is considered safe to take while breastfeeding as minimal amounts pass into breast milk. Dr. Mysore advises consulting with a healthcare provider to discuss individual circumstances but notes that metformin is generally considered safe for breastfeeding mothers. Multiple studies have examined the growth and development of breastfed infants whose mothers were taking metformin and found no adverse effects.
Jessica Madden, MD, a board-certified pediatrician and neonatologist, International Board-Certified Lactation Consultant (IBCLC) and Medical Director of Aeroflow Breastpumps, confirms that only a tiny amount of metformin passes into breast milk, so there is no need to wait after taking metformin to breastfeed or pump.
Benefits of Metformin for Breastfeeding Mothers
The primary benefit of metformin for breastfeeding mothers is its ability to stabilize blood sugar levels and prevent complications from diabetes. Metformin therapy is also sometimes used to treat polycystic ovary syndrome (PCOS), which has been linked to low milk supply in mothers attempting to breastfeed.
Read also: Berberine and Metformin
Potential Side Effects and Precautions
Metformin comes as a tablet taken two or three times a day, an oral solution taken one or two times a day, or an extended-release tablet taken once daily, all designed to maintain steady blood sugar levels throughout the day. Common side effects of metformin include:
- Nausea
- Vomiting
- Abdominal pain
- Bloating
- Dizziness
- Headache
- Hypoglycemia (low blood sugar levels)
- Symptoms of lactic acidosis (high lactate levels in the blood)
These side effects are the primary concerns whether breastfeeding or not. Contacting a healthcare provider is advisable if no side effects occur after starting metformin, as changes in blood sugar levels typically cause at least mild side effects.
While rare, monitoring for potential adverse reactions in breastfed babies is essential. However, Dr. Mysore notes that no adverse effects have been reported in breastfed infants whose mothers are taking metformin.
Dosing and Precautions
Since metformin is compatible with breastfeeding, no extra precautions need to be taken. If you were taking metformin before breastfeeding, continue taking it the same way, adhering to a set dosing schedule. If a dose is missed, take it as soon as remembered unless it is almost time for the next dose. As with any medication, discussing how you feel while taking metformin with your healthcare provider is crucial.
Breastfeeding Benefits for Mothers with Diabetes
Breastfeeding offers numerous health benefits for both mother and baby. Breastfeeding helps give your baby a head start to a healthier life. Even if you have diabetes, you can and should plan to breastfeed for at least six months. Breastfeeding can lower a mother’s risk of type 2 diabetes, high blood pressure, breast cancer, ovarian cancer, osteoporosis, and arthritis. It may also help you lose any weight you put on during pregnancy and recover from childbirth more quickly. If your baby is breastfed, they will be less likely to develop type 1 diabetes, overweight or obesity, and type 2 diabetes later in life. They’re also less likely to have asthma, eczema, respiratory disease, ear infections, and other serious health problems.
Read also: Comprehensive Study: Metformin and Phentermine/Topiramate
Diabetes Medications and Breastfeeding
Most diabetes medications are safe to use while breastfeeding, but some women with type 2 diabetes prefer to keep using insulin since it doesn’t get into your breast milk. Check with your health care provider about the amount of insulin to take since the amount you need may change. Breastfeeding may also make your blood glucose (blood sugar) levels a little harder to predict, so monitor it closely.
If your baby was born with low blood glucose (hypoglycemia), early breastfeeding and skin-to-skin contact with the mother are often the best treatments. This doesn’t mean they need formula supplementation or can’t be breastfed.
Formula Feeding as an Alternative
Yes, formula is also a good choice. Breastfeeding is sometimes more challenging than expected. But before completely switching to formula, getting breastfeeding support can help. Ask about peer groups and professional resources, such as a lactation consultant. Be sure to use a commercially prepared infant formula instead of making your own or using store bought milk that usually comes from a cow. The commercially prepared formulas are designed to provide the proteins, sugars, fats, and vitamins your baby needs, the same way breastmilk does. While formula feeding doesn’t offer all the benefits of breastfeeding, the most important thing is to nourish your child. If you have trouble breastfeeding at first or you don’t produce enough milk, discuss this with your OB/GYN or another health care provider. Keep trying to breastfeed while you supplement with formula or use donor milk. If your baby has trouble latching, you can also feed them breastmilk from a bottle which you will need to pump regularly.
Breastfeeding Tips for Mothers with Diabetes
- Breastfeed as soon as you can after delivery.
- Get lots of skin-to-skin contact with your baby and nurse several times a day in the beginning.
- Stay relaxed and try to be patient while your milk comes in.
- Have a snack before or during nursing. And keep something nearby to raise your blood glucose quickly, if your blood glucose may go low.
- Be sure to drink plenty of fluids to stay hydrated.
- Check your blood glucose levels before and after nursing.
Gestational Diabetes (GDM)
If you had GDM, you’re at higher risk for type 2 diabetes. See your health care provider to get tested one to three months after your baby is born. You can take steps to lower your risk, such as follow an eating plan, manage your weight, and be more active. Breastfeeding can reduce your risk for type 2 because it helps your body process glucose and insulin better. The longer you breastfeed also seems to affect your chance of developing type 2 diabetes. In one study, breastfeeding for longer than two months lowered the risk by almost half.
Medications and Breastfeeding: General Considerations
Breastfeeding is universally recognized as the preferred method of infant nutrition, but is sometimes abbreviated because of fear of harm to the infant from maternal medication. Comprehensive assessment can prevent unnecessary avoidance of breastfeeding, premature discontinuation of breastfeeding, or suboptimal treatment of the mother’s condition. The amount of medication that enters breast milk varies based on the maternal serum concentration and the pharmacologic properties of the medication.
Read also: Health Benefits of Metformin
Medications enter breast milk through diffusion from serum, so milk concentrations depend on maternal serum drug concentrations and diffusion characteristics. Few medications are actively transported into breast milk. Medications generally diffuse out of breast milk as the concentration in maternal plasma diminishes. The amount of medication that enters the infant through breast milk is determined by the medication concentration in the milk, volume consumed, and gastrointestinal absorption. In the early postpartum period, large gaps between mammary alveolar cells allow medication to enter the milk more readily. This effect is mitigated by the small volume of colostrum consumed. Topical medications are generally safer than oral medications, although medications applied to the nipple may be concerning. The infant’s health can alter the effect of exposure to maternal medication. A smaller exposure may be significant in an infant with less ability to metabolize medications.
Strategies to minimize infant exposure to maternal medication include dosing after breastfeeding and before the longest sleep interval for once-daily medications. Although pharmacologic knowledge can be helpful when prescribing medications for breastfeeding patients, use of up-to-date, accurate resources is essential.
When prescribing medications for a breastfeeding patient, those with the lowest risk to the infant should be selected, and dosing should be before the infant’s longest sleep interval. Prescribers should use current, accurate resources. LactMed is a convenient, government-sponsored, authoritative resource that lists safety information for many medications and is available free online.
Mental Health Medications and Breastfeeding
When mental health conditions occur during lactation, priority should be given to effectively treating the mother, often with medications that were effective during pregnancy.
Depression
The preferred approach for treating depression during lactation is to continue any treatment that was effective during pregnancy. Selective serotonin reuptake inhibitors are generally safe during breastfeeding. The most preferred are sertraline and paroxetine because these are the best studied, and they have low infant exposure and fewer adverse effects. Fluoxetine and its active metabolite have a long half-life and should be avoided if possible.
Anxiety
Antidepressant medications are commonly used to treat anxiety, but acute anxiety may be treated with benzodiazepines. Benzodiazepine use may rarely result in sedation of the breastfeeding infant, which must be weighed against the benefit of treating maternal anxiety.
Attention-Deficit/Hyperactivity Disorder
Although data for attention-deficit/hyperactivity disorder medications in breastfeeding are limited, methylphenidate appears to be the safest option if medical treatment is necessary. Methylphenidate is found in low levels in breast milk but not in infant serum.
Opioid Replacement Therapy
The benefits of breastfeeding while on opioid replacement therapy, including methadone and buprenorphine, outweigh the risks, especially during the current opioid epidemic. Potential adverse effects of opioid replacement therapy on breastfed infants include lethargy, respiratory difficulty, and poor weight gain.
Marijuana and Cannabinoids
Evidence regarding the effects of tetrahydrocannabinol in breast milk on infant development is limited and conflicting. Tetrahydrocannabinol is concentrated in breast milk, and breastfeeding infants have detectable levels. The use of marijuana can impair the ability to care for an infant effectively and safely. In many jurisdictions, marijuana use is reportable to child protective services. If marijuana use is continued, limiting the amount and avoiding direct inhalation by the infant are recommended.
Diabetes Medications During Breastfeeding: A Closer Look
Insulin, metformin, and second-generation sulfonylureas are not found in breast milk and are preferred when breastfeeding. Newer diabetes medications, including glucagon-like peptide-1 (GLP-1) receptor agonists and sodium-glucose cotransporter-2 (SGLT-2) inhibitors, have not been studied in lactation. These agents are large peptide molecules; therefore, the amount entering breast milk is presumably low and gastrointestinal absorption is unlikely. Manufacturers of SGLT-2 inhibitors do not recommend their use during breastfeeding because of the theoretical risk of injury to the infant’s developing kidneys. Medication labels recommend against the use of SGLT-2 inhibitors and GLP-1 receptor agonists during lactation.
Other Medications and Breastfeeding
Hypertension Medications
Medications for hypertension are generally acceptable to use during lactation. Calcium channel blockers pass poorly into breast milk. Diuretics used at the doses recommended for hypertension do not affect breast milk production and do not pass into the milk. Angiotensin-converting enzyme inhibitors do not pass significantly into breast milk. Angiotensin-receptor blockers are highly protein bound and are not expected to enter breast milk, but information is lacking regarding their use during lactation. Pending further study, they should generally be avoided in neonates and preterm infants. Excretion of beta blockers into breast milk can vary from drug to drug, and they are not typically first-line treatments for hypertension.
Upper Respiratory Medications
Topical treatments are the safest during lactation for upper respiratory symptoms. Nasal steroids such as fluticasone (Flonase) or budesonide are the safest and most effective treatments for allergic rhinitis while breastfeeding, because topical administration minimizes systemic absorption and infant exposure. Nasal saline, antihistamines, and cromolyn are safe but may be less effective. Management of asthma is not significantly changed during breastfeeding. Despite limited study, inhaled bronchodilator use is acceptable during breastfeeding because of low bioavailability and maternal serum medication levels after use. During exacerbations, oral or intravenous steroids may be used. The amount of prednisone in breast milk is very low and no adverse effects have been reported in breastfed infants. If the patient is taking high doses of steroids or has prolonged steroid use, breastfeeding should be delayed for four hours after a dose to decrease infant exposure.
Pain Medications
If an oral opioid is required for pain control, hydrocodone or morphine is preferred. When possible, patients should breastfeed their infants before taking opioids. Low doses should be used for short durations, and they should be avoided while using other sedating medications. Acetaminophen and ibuprofen are preferred analgesics during lactation. Maternal opioid use can cause infant sedation.
Antibiotics
Many commonly prescribed antibiotics are compatible with breastfeeding. There may be a risk of the infant experiencing an allergic reaction to the antibiotic or developing diarrhea because of changes in enteric flora. Hematochezia in infants exposed to intravenous clindamycin in breast milk has been reported. Because of the risk of bilirubin displacement and kernicterus, trimethoprim/sulfamethoxazole should be avoided in jaundiced, ill, stressed, or premature infants. Trimethoprim/sulfamethoxazole and nitrofurantoin should not be used while breastfeeding during the first month of life or in infants with glucose-6-phosphate dehydrogenase deficiency to prevent the risk of hemolysis. Cephalosporins are a safer alternative. Candida infections and diarrhea may be more common in infants exposed to metronidazole (Flagyl). The calcium in breast milk decreases the oral absorption of fluoroquinolones and doxycycline.
Herbal Supplements
Herbal products, particularly galactagogues, are frequently used to increase milk production. Herbal supplements are concerning for risk of impurities and lack of study of effects on breastfed infants.
Contraceptives
Nonhormonal contraceptive methods such as barrier methods or a copper intrauterine device (Paragard) are preferred during lactation, especially for the first four to six weeks postpartum. When an intrauterine device is inserted immediately postpartum, the risk of expulsion is likely higher in breastfeeding patients. The estrogen in oral contraceptives does not affect the composition of breast milk or infant growth and development but may decrease milk production. Progestin-only contraceptives, including the levonorgestrel-releasing intrauterine system, 52 mg, and etonogestrel subdermal contraceptive implant (Nexplanon), are the hormonal contraceptives of choice during breastfeeding to avoid potential complications of thrombosis and decreased milk supply from estrogen exposure. Acceptable timing of postpartum initiation of hormonal contraception is controversial.
Radiologic Imaging
Breastfeeding patients sometimes undergo radiologic imaging with contrast. The amount of iodinated and gadolinium contrast excreted into breast milk and absorbed by the infant gastrointestinal tract is expected to be small; therefore, both agents are considered compatible with breastfeeding. Radiopharmaceuticals, such as those used for thyroid or cardiac scanning, are concerning for the breastfeeding infant who may be exposed through breast milk ingestion and close maternal contact.
Metformin and Fertility
Based on the studies reviewed, is it not known if metformin can make it harder to get pregnant. One study suggested that men given a prescription for metformin in the 3 months before conception might be associated with genital defects in the infant. However, no higher chance for birth defects was reported in a different study that looked at ~1,700 children of men who were prescribed metformin to treat type 2 diabetes in the 3 months before conception. Prescription based studies cannot tell us if the person actually took the medication or if they took it correctly. In general, exposures that men have are unlikely to increase the risks to a pregnancy.
Metformin During Pregnancy
Sometimes when women find out they are pregnant, they think about changing how they take their medication, or stopping their medication altogether. However, it is important to talk with your healthcare providers before making any changes to how you take this medication. High blood sugar levels before and during pregnancy increase the chance of birth defects and other complications.
Metformin is not expected to increase the chance for miscarriage. Every pregnancy starts out with a 3-5% chance of having a birth defect. This is called the background risk. Use of metformin during pregnancy is not expected to increase the chance of having a baby with a birth defect. Some studies have suggested women with gestational or type II diabetes who were treated with metformin had smaller babies at the time of delivery than those who were treated with insulin. The children exposed to metformin during pregnancy quickly gained weight after birth. Some studies have shown that children exposed to metformin during pregnancy may have a higher chance of having obesity in childhood.
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