Drug distribution in human milk

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Editor, – It was disappointing to find that the informative article 'Drug distribution in human milk' (Aust Prescr 1997;20:35-40) did not contain information regarding either oral or inhaled corticosteroids. For many lactating women with asthma, it is essential to maintain inhaled steroid medication and to treat acute exacerbations of asthma with increased doses. These drugs currently carry a B3 listing in the 'Medicines in Pregnancy' publication.

The prescribing information for budesonide states that 'there is no information available on the passage of budesonide into breast milk. It is recommended therefore that breast feeding be discontinued in women receiving budesonide'. This wording has the potential to alarm mothers and their doctors and to result in inappropriate advice to breast-feeding mothers. In view of the evidence suggesting that breast feeding may protect against the development of asthma, this is a double jeopardy.

Is it possible that this wording could be altered in keeping with clinical experience, which suggests that these medications do not pose a risk to the babies of breast-feeding mothers with asthma who are taking inhaled corticosteroids? Can the authors provide any information which informs us of the risk of breast feeding in women taking oral corticosteroids? The current prescribing information for most of the oral steroids suggests that administration to breast-feeding mothers is not recommended. Clinical experience tells us that it is not recommended to withhold oral steroids in asthma exacerbations.

Christine Jenkins
Thoracic Physician
North Sydney, N.S.W.

Susan Parker, Medical Information Manager, Astra Pharmaceuticals, comments:
Thank you for the opportunity to respond to Dr Christine Jenkins' letter regarding the wording of the information about breast feeding in the product information for budesonide.

Drug treatment during pregnancy and lactation continues to be an area of limited data, based on experiential rather than experimental science. Unfortunately, because there are no clinical data available on the passage of budesonide into breast milk, we have no data on which to base a request to the Therapeutic Goods Administration (TGA) to amend the product information.

Astra Pharmaceuticals would be happy to work with respiratory physicians to obtain data regarding the passage of budesonide into breast milk so that the statement may be amended to be more practical.

Alternatively, we would be happy to approach the TGA in an attempt to include a statement similar to that for fluticasone such as: In view of the pharmacokinetic profile, transfer into breast milk is unlikely.

It is interesting to note that the product information for products containing beclomethasone dipropionate do not include any lactation statement.

The Editor comments:
Based on information supplied by the New South Wales Medicines Information Centre, it would appear that inhaled corticosteroids can probably be used safely by women who are breast feeding. While the milk: plasma ratios are unknown, the concentrations secreted into milk following normal inhaled doses are probably small.

Prednisolone is secreted into breast milk, but, following a single 5 mg dose, only 0.2% appears in the milk. The milk: plasma ratio may increase with increasing serum concentrations, but exposure is probably minimal for daily doses of 20 mg. As prednisone requires conversion into prednisolone, the latter is probably preferred during lactation.

The lack of data on the safety of inhaled and oral steroids taken during breast feeding should be discussed with asthmatic mothers. They can then decide if the known benefits of breast feeding and good asthma control outweigh the probably small risk of adverse effects.