General information on drug use in breastfeeding: nonprescribed drugs

In this topic:

Introduction

Alcohol

Nicotine

Caffeine

Cannabis

Amphetamine and methamphetamine

Introduction

The postnatal period may represent an opportunity for the clinician to discuss the modification of maternal drinking and smoking behaviours. Every effort should be made to capitalise on a woman's motivation to enter treatment during this time.

Educational and behavioural interventions should be the mainstay of treatment. Pharmacological treatments should only be considered after specialist consultation.

Alcohol

Findings in this area are complicated by the fact that alcohol consumption during breastfeeding often represents a continuation of consumption during pregnancy, making it difficult to separate adverse effects on the infant from each period. Confounders such as smoking also make interpretation difficult.

Alcohol has been associated with delayed let-down reflex and reduced breast milk supply, probably related to inhibition of oxytocin and prolactin release. Thus, in contrast to a prevailing folklore in many cultures of the benefits of alcohol for milk production, the opposite is more likely the case.

The infant's liver maturation is not complete until approximately three months, and the resultant decreased capacity to metabolise alcohol could potentially lead to accumulation. Both excessive drowsiness and irritability have been described in breastfed infants whose mothers consume alcohol.

Both animal and human studies point towards potential adverse long-term effects in the offspring. Significantly poorer development of motor skills has been reported in breastfed infants of mothers who consumed one standard drink per day. There is also evidence (both human and animal) that exposure to alcohol in breast milk is associated with subsequent active seeking of alcohol. Whether this translates into earlier initiation of drinking in later life (eg adolescence) is unclear.

A safe level of alcohol consumption during breastfeeding has not been defined. The clinician is faced with a dilemma in terms of weighing up the relative harms and benefits of breastfeeding in women who regularly consume alcohol.

The safety of the anticraving drugs naltrexone and acamprosate has not been established in breastfeeding.

Nicotine

In Australia, over half of women who quit smoking during pregnancy resume smoking in the postnatal period. This is thought to be due to postnatal smoking being perceived as more socially acceptable (as compared to pregnancy), as well as smoking being seen as helpful for losing weight. The powerful influence of having a partner who smokes has also been emphasised.

There is a well-established dose–response relationship between the number of cigarettes smoked and reduced likelihood or duration of breastfeeding.

Smoking has a number of adverse effects upon lactation in terms of decreased production, interference with the let-down reflex and altered taste of breast milk (which the infant may refuse). The infant may be affected through both nicotine in the milk and side-stream smoke. The effects may include colic, diarrhoea, tachycardia, irritability, apnoeic episodes and immune system impairment. These are especially likely if the woman smokes more than 15 cigarettes per day.

There is debate as to whether or not the adverse effects of nicotine in breast milk are outweighed by the benefits (especially immunological ones) to the infant of being breastfed. It has been argued that if a woman cannot cease smoking during the postnatal period she should nevertheless still breastfeed. The resultant boosted immunological competence of the infant has, in some studies, been shown to be protective against the increased risk of respiratory tract infection resulting from passive smoking. Delaying smoking until after having just breastfed the baby will minimise the nicotine available in the milk by the time of the next breastfeed.

Ongoing exposure to cigarette smoke in the postnatal period is a well-recognised risk factor for sudden infant death syndrome (SIDS).

The use of nicotine replacement therapy (NRT) during breastfeeding remains controversial. Serum concentrations of nicotine in breastfed infants of mothers using NRT are low (approximately 6% of maternal serum concentration), possibly due to the infant's first pass metabolism of oral nicotine. Moreover, the milk will not contain other cigarette-derived toxic substances. The additional benefits for a young baby in a nonsmoking household should also be taken into account (eg reduced risk of SIDS). If nonpharmacological measures are unsuccessful, consideration of the use of NRT is warranted. Rather than patches, intermittent regimens are sometimes advocated to allow breastfeeding to precede nicotine dose.

Data suggest that infant bupropion dose from breastfeeding is approximately 2% of maternal dose. Using the guideline that less than 10% is likely to be safe for most drugs, this is reassuring. A small number of case reports have found bupropion undetectable in the serum of breastfed babies whose mothers were taking the drug. However, bupropion has several active metabolites and further data are required to fully establish safety in breastfeeding.

Caffeine

Caffeine is readily transferred into breast milk, and young infants have lower capacity to metabolise it, which raises the possibility of caffeine toxicity. Infants breastfed by mothers ingesting more than 300 mg/day (2 to 3 cups of coffee) may become jittery, restless and experience sleep difficulties. No long-term adverse effects have been documented. Conflicting findings have emerged regarding the relationship between caffeine and SIDS, and confounding factors (eg smoking) may explain the association found in one study, which was unable to be replicated. For information on the approximate caffeine content in drinks and other preparations (see Caffeine use in pregnancy).

Cannabis

Cannabis passes readily into breast milk. Animal studies have repeatedly demonstrated adverse effects on the rapidly developing infant brain. Human data are difficult to interpret due to confounding factors (including side-stream smoke) but appear to support the detrimental neurocognitive impact.

Amphetamine and methamphetamine

There are very few data on amphetamine and methamphetamine. One study of four babies breastfed by mothers on dexamphetamine reported that this was readily transferred, but relative infant dose was less than 10% (which is generally considered acceptable in the short term). No adverse infant effects were observed.