Mothers often ask their anaesthetist for information about breastfeeding after anaesthetic and surgical interventions. The majority of drugs administered to the mother enter her breast milk, but many are present in pharmacologically insignificant amounts and do not therefore pose a risk to the baby. The amount of drug that a breastfed baby receives depends on the concentration of drug in the milk and the volume of milk taken by the baby. In the first few days following delivery, the baby receives colostrum and then very small volumes of milk, so that any drug exposure is likely to be minimal. It is, however, common sense to administer drugs to the breastfeeding mother only if they are considered essential.
The British National Formulary (BNF) contains a comprehensive list of drugs that are known to be present in breast milk following maternal administration, but also points out that in many cases there are insufficient data to enable accurate information to be provided.
Breastfeeding and anaesthesia
Production of breast milk is dependent on adequate maternal hydration and regular stimulation (either by the baby feeding or by the mother expressing her milk). A mother scheduled for anaesthesia and surgery should be encouraged to feed her baby as near as possible to the planned time of surgery and also as soon as she feels able to postoperatively. In some cases it may be more appropriate for her to express milk preoperatively if the procedure or recovery period is expected to be long.
There is some evidence to suggest that following a caesarean section under regional anaesthesia compared with general anaesthesia, mothers are able to breastfeed more quickly; this is presumed to be due to the maternal and neonatal effects of general anaesthesia, but more research is required in this area. It has been proposed that babies born to mothers receiving epidural analgesia in labour are more likely to have delayed breastfeeding, but the evidence for this is extremely weak.
Intravenous and inhalational agents
Both thiopental and propofol are found in breast milk in insignificant amounts following maternal administration, and current data suggest that a mother can breastfeed as soon as she has adequately recovered from a general anaesthetic. Levels of volatile agent excreted into breast milk are also negligible (most information relates to halothane, but extrapolation of data based on pharmacokinetic information suggests that isoflurane, sevoflurane and desflurane would be present in breast milk in even lower concentrations). Neuromuscular blocking agents are large, water-soluble, ionized quaternary ammonium compounds and therefore are not excreted into breast milk in any measurable quantity.
Analgesics
Transfer of non-steroidal anti-inflammatory drugs and paracetamol into breast milk has been extensively studied, and neither type of analgesic is present in clinically important quantities.
Therapeutic doses of morphine and diamorphine given for postoperative analgesia (following either caesarean section or other surgical intervention) can be given to the mother as required, though the lowest effective dose for shortest duration should be administered. For those who require opioid analgesia for a longer period, it would be sensible to monitor the neonate for signs of opioid side effects. Longer-acting opioids given more than an hour before delivery may inhibit the neonatal suckling reflex. Codeine is no longer recommended for use in breastfeeding mothers because of the possibility of the mother or neonate being a rapid metaboliser, leading to supratherapeutic levels of morphine. The Medicines and Healthcare products Regulatory Agency (MHRA) currently recommends the prescription of tramadol or dihydrocodeine (at the lowest effective dose) instead, though evidence for their use remains limited. Maintenance on a methadone programme is not considered incompatible with breastfeeding, and there are no longer any restrictions on the maximum dose considered safe, although the lowest dose possible is generally recommended.
Antiemetics
All the commonly used antiemetics carry a manufacturers’ warning to ‘use with caution’ or ‘use only if essential’.
Benzodiazepines
Prolonged administration of benzodiazepines should be avoided because of the risk of neonatal toxicity and withdrawal symptoms. Diazepam is found in clinically significant quantities in breast milk and may cause hypotonia and impaired suckling in the baby. However, use of a single dose of temazepam or lorazepam as a premedicant drug is not contraindicated. Similarly, use of midazolam for intravenous sedation or during general anaesthesia is considered safe.
Other drugs
Anticoagulants
Warfarin and low-molecular-weight heparins are considered to be safe in breastfeeding mothers.
Antidepressants and anticonvulsants
The reports of the Confidential Enquiries into Maternal Deaths have highlighted the risk of postnatal depression and its potential to lead to postnatal psychosis and suicide. There are numerous case reports offering conflicting advice about the use of psychotropic and anticonvulsant drugs in lactating women. Since the recommendations vary with each individual drug, specialist advice should be sought.
Antihypertensives
It is common for pre-eclamptic women to receive β-blocking drugs for several weeks following delivery. Atenolol is excreted in breast milk in measurable amounts, and there is some evidence that it may cause neonatal bradycardia, hypotension or cyanosis; the World Health Organization advises using an alternative agent, particularly when the infant is less than 1 month old, given the immature renal function.
Key points
• Most drugs are excreted into breast milk, but information about the effects on the neonate is scarce.
• Commonly used anaesthetic and analgesic drugs can be safely used in breastfeeding mothers.