To the Editor: Although many medicines transfer into breast milk, the amount received by the breastfed infant is usually low, with minimal risk to the infant.1 Because medicines are not tested on breastfeeding women, product information often states that the safety of use during lactation is unknown. This may lead to over-caution in prescribers, who may incorrectly advise women to stop breastfeeding during courses of medication.2 Even brief interruptions to breastfeeding can lead to complications, such as mastitis or breast refusal.1,2

Evidence-based assessments should be made for each mother–baby pair, depending on the baby’s age and the drug’s pharmacokinetics.2 Information about the safety of medicines during breastfeeding is available from books and websites,3 but doctors’ knowledge and use of these resources are not known. We carried out an observational study to describe general practitioners’ current and preferred sources of information about the safety of medicines during breastfeeding.

We surveyed the 640 GPs who provided shared maternity care at Victoria’s largest maternity hospital, the Royal Women’s Hospital (RWH), Melbourne. A postal survey to be completed anonymously was sent in November 2007 with a reminder postcard 2 weeks later; a second copy of the survey was sent in February 2008. The study was approved by the human research ethics committees at La Trobe University, University of Melbourne and the RWH.

Responses were received from 52% of GPs (335/640); most respondents were women (70%, 233/333), and most had personal experience of breastfeeding for longer than 6 months (68% of participants or their partners, 227/333). Over two-thirds (70%, 233/335) used the Internet during consultations. Eighty-two per cent (270/331) found the Internet helpful.

Most participants (73%) obtained information about medicines and breastfeeding from their software program, or from dedicated books (61%; predominantly the RWH’s Drugs and breastfeeding4), and 51% used telephone advice (predominantly from the RWH pharmacy). When asked where they would prefer to access this information, most nominated their software prescribing program (68%) or a reliable Internet database (57%) in their top three preferences (Box).

Although most participants (89%, 293/331) felt confident about prescribing for breastfeeding women, the majority were not aware that ibuprofen is considered safe for breastfeeding women; only 31% (102/330) agreed that “there is no problem taking this medicine while breastfeeding”. It appeared that some GPs erroneously believed that pregnancy drug ratings also apply to breastfeeding women. Ibuprofen has a category C pregnancy rating (drugs that have caused or may be suspected of causing harmful effects in the human fetus or neonate without causing malformations), yet the product information from Reckitt Benckiser (Slough, United Kingdom), the manufacturer of Nurofen, states that “no harmful effects are known in breastfed infants”.5 An additional problem is the contradictory advice given by different sources;6 another manufacturer, Abbott, does not recommend ibuprofen for breastfeeding mothers.5

As recommended by researchers in the United States, “We should replace the assumption ‘when in doubt, don’t breast-feed’ with the mandate ‘when in doubt, look it up in a reliable source’”.6 A central accessible source of up-to-date information about individual medications and lactation is urgently needed.7 Most GPs in our study would like this information available on the Internet.