Prescribing During Breastfeeding

Prescribing during breastfeeding aims to treat the mother effectively while keeping infant exposure low enough to avoid harm. Most medicines are compatible; interrupting breastfeeding is rarely needed and carries its own risks to infant nutrition, immunity and, in East Africa, survival.

Transfer into milk. Favoured by low molecular weight, low protein binding, high lipid solubility, weak basicity and long half-life. Milk is slightly acidic, so weak bases concentrate in it (ion trapping).

Relative infant dose. Infant dose (mg/kg daily) divided by maternal dose (mg/kg daily) as a percentage. Under 10% is generally acceptable; many common drugs are under 2%.

Infant factors. Preterm infants, neonates under 2 months and infants with renal, hepatic or respiratory disease clear drugs poorly and need closer review. Oral bioavailability in the infant also matters; gentamicin and heparins are barely absorbed.

Colostrum phase. In the first 3 to 4 days the volume of milk is small, so total infant exposure is low even when cell junctions are open.

Analgesia. Paracetamol 1 g orally every 4 to 6 hours, maximum 4 g daily. Ibuprofen 400 mg orally every 6 to 8 hours, maximum 1.2 g daily (2.4 g daily under supervision). Morphine short courses at the lowest dose; avoid codeine and tramadol.

Antibiotics. Penicillins, cephalosporins, macrolides, clindamycin, nitrofurantoin (avoid if infant has G6PD deficiency or is under 1 month with jaundice), metronidazole at usual doses, gentamicin. Single 2 g metronidazole dose: express and discard for 12 to 24 hours.

Hypertension after birth. Enalapril 5 mg once daily, up to 20 mg twice daily; nifedipine modified release 20 to 40 mg twice daily; amlodipine 5 to 10 mg once daily; labetalol 100 to 400 mg 2 to 3 times daily. Change methyldopa to another agent within 2 days of birth because of depression risk.

Depression and anxiety. Sertraline 50 mg daily up to 200 mg daily, or paroxetine 20 mg daily up to 50 mg daily, have the lowest infant levels. Continue an antidepressant that worked in pregnancy rather than switching.

Contraception. Progestogen-only methods at any time: etonogestrel or levonorgestrel implant, levonorgestrel or copper intrauterine device (within 48 hours or after 4 weeks), medroxyprogesterone acetate 150 mg IM every 12 weeks, desogestrel 75 micrograms daily. Combined hormonal methods only from 6 weeks (many advise 6 months) as oestrogen can reduce supply and raises early thrombosis risk.

Low milk supply. Correct feeding technique first. Domperidone 10 mg orally 3 times daily for up to 7 days is used in some regions; it prolongs the QT interval and is avoided in cardiac disease, with QT-prolonging drugs or strong CYP3A4 inhibitors.

Lactation suppression (when needed). Cabergoline 1 mg orally as a single dose on day 1 after birth, or 250 micrograms every 12 hours for 2 days once lactation is established. Avoid in hypertension and pre-eclampsia.

HIV. Breastfeeding is supported on suppressive antiretroviral therapy, with exclusive breastfeeding for 6 months and continued breastfeeding to 24 months in many East African programmes. Maternal viral load monitoring and infant prophylaxis (nevirapine with or without zidovudine) follow local schedules.

Avoid. Codeine and tramadol (ultra-rapid CYP2D6 metabolisers produce high morphine or O-desmethyltramadol levels; neonatal deaths reported). Amiodarone (iodine load, long half-life). Radioactive iodine and most radiopharmaceuticals (interrupt for a set period). Cytotoxic chemotherapy. Ergotamine. High-dose aspirin (Reye syndrome risk). Iodine-containing antiseptics on large areas.

Use with care and infant monitoring. Lithium (infant levels, thyroid and renal function). Lamotrigine (infant levels up to 30 to 50% of maternal; watch for rash and apnoea). Benzodiazepines (prefer short-acting lorazepam or oxazepam at low dose). Clozapine (agranulocytosis and sedation in the infant). Sedating antihistamines.

Reduce supply. Combined oestrogen methods, pseudoephedrine, cabergoline and bromocriptine, high-dose diuretics.

Interactions. Rifampicin and enzyme-inducing antiepileptics reduce progestogen implant and pill efficacy; use a copper or levonorgestrel intrauterine device or medroxyprogesterone injection.

Special groups.

• Preterm or unwell infants: prefer drugs with relative infant dose under 2% and short half-life.
• Maternal kidney or liver impairment: higher maternal levels mean higher milk levels; adjust maternal dose.
• Regional: CYP2D6 ultra-rapid metaboliser genotype is markedly more common in some North-East African populations, notably in Ethiopia, which strengthens the case against codeine and tramadol.

Infant monitoring. Feeding, weight gain, sleepiness, irritability, rash, diarrhoea and oral thrush. Measure infant serum levels for lithium, lamotrigine, clozapine or phenobarbital if the infant is unwell.

Dose timing. Take once-daily medicines just after the longest feed, often at night, to reduce peak exposure.

Stopping rules. Stop the medicine or pause breastfeeding if the infant is excessively sleepy, feeds poorly or breathes slowly after maternal opioid, benzodiazepine or sedating drug use; seek urgent review.

Referral and escalation. Discuss with a specialist lactation pharmacist or medicines information service before cytotoxics, radiopharmaceuticals, immunosuppressants without data, or when the infant is preterm or unwell.