All drugs transfer into milk. The extent is less than drug transfer during pregnancy.
General Advice
  • For general advice, see Individualising Drug Therapy. Consider non-medicine measures first, and avoid all drug therapy if possible.
  • The infant benefits from breastfeeding (nutritional and immunological value) particularly in the first year of life.
  • The infant does not usually benefit from medicine exposure via breast milk.
  • The infant risk depends on the dose ingested via milk; and the medicine’s oral availability and clearance in the infant. The extent of drug transfer is less during breastfeeding than during pregnancy.
  • Monitor the infant for adverse effects of the medicine (e.g. failure to thrive, sedation, diarrhoea). Document any possible adverse effects, and reassess the infant risk and mother’s benefit, depending on symptom and severity.
  • Dose to minimise medicine exposure with respect to feeds. Concentrations in the milk usually follow concentrations in maternal plasma.
  • Medicine therapy rarely constitutes a reason to avoid breastfeeding in full-term healthy babies.
  • An infant dose < 10% of the maternal dose on a mg/kg basis – relative infant dose (RID) – is considered “safe” for medicines that are not highly toxic.
  • Cytotoxic drugs with low RID are not considered “safe” (because they are highly toxic).
  • Consult when the infant is premature, has significant renal or hepatic disease or G6PD deficiency, or when the maternal dose is unusually high or poorly controlled (e.g. social drugs).
Medicines considered “safe” when breastfeeding full-term healthy babies
The following is a guide only and the list is not exhaustive.
Class Examples of individual medicines
Analgesics paracetamol, diclofenac, ibuprofenopioid analgesics* (short courses < 2 days): morphine, oxycodone, codeine#
Anticoagulants enoxaparin, heparin, warfarin
Antiepileptic drugs* carbamazepine, lamotrigine, levetiracetam
Antidepressants* SSRIs: citalopram, escitalopram, paroxetine, sertralineSNRIs: venlafaxine

tricyclics: amitriptyline, nortriptyline

Antidiabetic insulin, metformin
Antihistamines cetirizine, loratadine
Antihypertensives ACE inhibitors: enalapril, perindoprilbeta blockers: labetalol, metoprolol, propanolol

calcium channel blockers: diltiazem, nifedipine

methyldopa

clonidine (if taken during pregnancy or under specialist care)

Antimicrobials betalactams: amoxicillin, flucloxacillincephalosporins: cefalexin, ceftriaxone, cefazolin, cefuroxime, cefotaxime, cefepime, ceftazidime

macrolides: azithromycin, clarithromycin, erythromycin, roxithromycin

metronidazole (shorter courses – e.g. 400 to 600 mg BD for 7 to 10 days; if using a 2000 mg dose, ideally avoid breastfeeding for 12 hours)

nitrofurantoin

trimethoprim, trimethoprim/sulfamethoxazole

aciclovir, valaciclovir

Antipsychotics* haloperidol, olanzapine, quetiapine, risperidone
Hypnotics* short courses (< 2 days) of midazolam, temazepam, zopiclone
Cardiac glycoside digoxin
Contraceptives progestogen-only, combined oral contraceptives once breastfeeding has been established
Corticosteroids (short courses) prednisone (≤ 40 mg/day)
Gastrointestinal drugs domperidoneproton pump inhibitors: omeprazole, pantoprazole

mesalazine

Immunosuppressants

azathioprine, mercaptopurine, thioguanine

hydroxychloroquine

* For all, monitor infant for adverse effects (e.g. sedation, jitteriness, lethargy, poor feeding).

# Codeine use in breastfeeding is controversial. However, drug concentration data show that short courses are likely to be safe.

Medicines considered “unsafe” during breastfeeding
amiodarone
cytotoxic drugs
ergotamine
iodine-containing X-ray contrast media
medicines used during nuclear medicine exams
opioids (long courses > 2 days and/or doses > 20 mg oral morphine or equivalent)
lithium (requires infant drug concentration monitoring)
retinoids (e.g. isotretinoin)
social drugs (e.g. alcohol, cannabis)