Medication Safety While Breastfeeding: general principles

Written By Sophie Mace

Medication safety while breastfeeding is an area that is often unnecessarily controversial, and rife with miscommunication. Many health practitioners, simply not understand the underlying principals of drug safety in lactation, will advise breastfeeding parents to “pump and dump”, prematurely wean before starting medications, or withhold important medications “just in case”.

The main problems here are pretty clear when we consider that the majority of medications are safe to take while breastfeeding; women are either denied beneficial/necessary medications while they’re lactating, or they are forced to prematurely stop breastfeeding, with all the emotional and physical risks this entails for them and their baby. Pumping and dumping - expressing breastmilk then pouring it out - is time-consuming and stressful (if not downright distressing) and requires that either the whānau has stored breastmilk already or can give formula during the “dumping” period.

Below, I go into the general principles of determining medication safety during breastfeeding and then give some resources for health professionals and/or parents to help guide shared decision-making. Feel free to skip the background info and go straight to the resources at the end!

TL;DR: almost all medications are safe to take while breastfeeding, with a few exceptions, such as chemotherapy. The risk of not medicating, and the risk of early cessation of breastfeeding, should always be considered along any potential drug risks.

  • Does the medication get into breastmilk in any great amount?

The majority of medications will transfer into breastmilk to some degree. The amount that transfers depends on a number of factors, including the concentration of the drug in the parent’s bloodstream, the size of the medication itself (smaller molecular weight = more diffusion), protein binding (medications that are predominantly bound to proteins in the plasma, such as warfarin and NSAIDs, are less likely to diffuse as only the free/unbound drug can move), whether they are water- or lipid-soluble (lipid soluble = more diffusion), and whether there is an active transfer process (such as with iodine).

The concentration of most medications in the breastmilk will be in constant flux, dependent on the concentration in the parent’s bloodstream. Some medications will preferentially stay in the milk once there (because of the lower pH of breastmilk), though this isn’t the norm; for most, remember “the breast is not a bladder” - breastmilk is a living fluid that is constantly changing.

Medications with a short half-life (that are cleared from the parent’s bloodstream relatively quickly) will exit the milk sooner; be aware that some medications have a longer half-life in a baby than in adult, however, and that some drugs will accumulate in the baby even if the parent clears them faster.

  • Does it get absorbed from the baby’s gut?

Some medications are present in breastmilk that will never make it into the baby’s system because they’re not absorbed from the gut (poor oral availability). As a general rule, medications that need to be given via injection (e.g. monoclonal antibodies), are unlikely to be a problem because they’re not absorbed from the gut. Other medications are largely broken down in the stomach and upper intestine and never make it far enough to be absorbed. The “Relative Infant Dose (RID)” is used to try and quantify this - in general, an RID of <10% is considered safe (depending on the medication itself, of course).

An important caveat is that some medications can act on the gastrointestinal tract and cause side effects even if not absorbed, causing diarrhoea, constipation and rare syndromes like pseudomembranous colitis.

Advising a parent not to breastfeed after local anaesthetic or botox is non-sensical; if these drugs are entering the bloodstream in any significant amount, you have much bigger issues on your plate!

  • How much milk is the baby actually drinking?

This is particularly relevant to newborns and toddlers or babies who are mixed-feeding.

While medications tend to pass more freely into colostrum than mature milk (because of the larger spaces between breast alveolar cells), the total amount of milk ingested is low and therefore, the total dose is lower. For babies who are mixed feeding or toddlers who are often drinking less volume, the total amount of medication they receive will also be lower.

  • Is it safe for the baby if they absorb it?

This one is pretty obvious when you think about it but seemingly not always considered. Many medications women are told to avoid are actually commonly given to infants/babies and are safe. Consider paracetamol, ibuprofen, antibiotics and caffeine: All are completely safe when given to infants, but many breastfeeding parents avoid them!

  • Is the medication necessary?

I’ve put this so low because I think the majority of breastfeeding parents aren’t taking unnecessary medications. But this is something that especially needs to be considered with herbal medications and high-dose vitamins or supplements, or recreational drugs.

  • Does it impact on breastmilk production?

Some medications are safe for the infant, but may impact on breastmilk production. Common examples include the combined oral contraceptive pill (COCP), pseudoephedrine, cabergeline, and domperidone.

  • Is it safe for bedsharing?

I include this specifically, although it’s not about breastfeeding directly, because we know the majority of parents bedshare at some point, intentionally or otherwise. Some medications, particularly sedating ones, are not considered safe while bedsharing and should be avoided where possible. These include some anti-anxiety medications, anti-histamines, or anti-psychotics, and is relevant for breastfeeding, mixed feeding and bottle feeding dyads.

  • What is the risk of stopping breastfeeding?

The risks of formula feeding to an infant are well known and documented and should not be dismissed when it’s not necessary for formula to be introduced. Further, there are emotional and physical risks to birthing parents who don’t breastfeed or who prematurely wean and this should always be considered and discussed; not to demonise formula or judge parents who give formula, but because parents deserve to have this sort of information and be able to make an informed decision about their feeding practices.

  • What are the risks of not medicating?

Lastly, and possibly even the most important question to ask. What are the risks of not medicating?

Other medications, such as anti-depressants or stimulants for ADHD, are often withheld unnecessarily until a parent chooses to stop breastfeeding. This may be driven by comments from the health professional, pharmacist, or concerns from the breastfeeding parent or their whānau. However, the risk of not medicating isn’t often considered, and these risks can be significant. For example, the risk of untreated ADHD includes a significantly higher risk of car accidents, speeding, accidental injury (and even accidental death), perinatal anxiety and depression, overwhelm and dissociation, and emotional dysregulation. The risks of untreated perinatal anxiety and depression are well documented and can have long-lasting effects on the parent, infant, and their wider whānau.

Resources

Sophie Mace
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