Letter to the Editor
Editor, – With regard to the editorial ‘Classifying drugs in pregnancy’, we would like to comment on the statement that ‘topical or inhaled exposures are generally less concerning than oral or parenteral ones’. While this is an accepted generalisation, important exceptions should be highlighted including topical retinoids and cytotoxics, as well as transdermal opioid patches.
According to several resources, topical tretinoin and isotretinoin (Australian category D) are not recommended during pregnancy.1-4 The Australian Medicines Handbook states that ‘although absorption via skin is minimal, in view of the teratogenicity of systemic retinoids, topical retinoids should not be used in pregnancy’. This is in line with the manufacturers’ recommendations.
Topical 5-fluorouracil cream (Australian category D) is another important example. Spontaneous abortion and two cases of malformations in infants exposed in utero due to maternal application of the cream have been reported.1
Safety concerns of using transdermal fentanyl patches (Australian category C) during pregnancy should also be considered as the patch is designed to provide equivalent serum concentrations to parenteral formulations. The product information for Durogesic states that ‘neonatal withdrawal syndrome has been reported in newborn infants with chronic maternal use of Durogesic during pregnancy’.
Hunter Drug Information Service
Calvary Mater Newcastle Hospital
Letter to the editor
Editor, – The recent editorial by Debra Kennedy (Aust Prescr 2014;37:38-40) describes a longstanding and complex problem in medicines information. Unfortunately, Dr Kennedy’s understanding of content found in the Australian Medicines Handbook (AMH) – that it ‘essentially consists of the Australian Drug Evaluation Committee categorisation and the company product information' – is incorrect.
Great care and significant consideration of available evidence is taken in crafting the brief advice we provide. In the section on prescribing for pregnant women we say:
Our advice is based on human data and clinical experience. Animal studies are not used as the sole sources of information upon which advice is based, as their interpretation with respect to human risk is not clear. Advice provided may not mirror the approved product information. Absence of information in AMH does not imply safety. Australian categories of safety, from the database Prescribing medicines in pregnancy, are included where they exist.
For nifedipine, the product information states ‘Category C: nifedipine is contraindicated throughout pregnancy’. It then describes a range of potential fetal impacts on the basis of maternal hypotension, and adverse fetal effects seen in animal species.
However, the AMH advises nifedipine is ‘used to suppress preterm labour and for hypertension in pregnancy’. This reflects current evidence and practice, as nifedipine is the preferred tocolytic in Australia. The AMH also includes preterm labour as an accepted indication for use of nifedipine.
It is impossible to reduce complex information to a one-letter categorisation. The plan announced by the US Food and Drug Administration over five years ago, to eliminate the pregnancy categorisation, and replace it with drug-specific interpretations of available data, confirms this.
- Briggs GG, Freeman RK, Yaffe SJ. Drugs in pregnancy and lactation: A reference guide to fetal and neonatal risk. 9th ed. Philadelphia, USA: Lippincott Williams & Wilkins; 2011.
- Australian Medicines Handbook. Adelaide: Australian Medicines Handbook Pty Ltd; 2014.
- eMIMS. Sydney: MIMS Australia Pty Ltd; 2014.
- Bozzo P, Chua-Gocheco A, Einarson A. Safety of skin care products during pregnancy. Can Fam Physician 2011;57:665-7.