Correspondence: Pregnancy; Polypharmacy

Questions about the safety of medicines in pregnancy arise when a pregnant woman is already taking an established treatment, or when a new medicine is being considered to treat a condition that occurs during pregnancy.

The medicine’s Safety Data Sheet usually contains some information about use during pregnancy but this is often insufficient to guide decision making. Manufacturers are not going to recommend a medicine’s use in pregnancy if there is any uncertainty or the absolute safety cannot be guaranteed or proven. However, if the medicine is known to be teratogenic in humans or contraindicated in pregnancy this should be clearly stated in the data sheet.

The level of information required will depend on the clinical context. For more complex scenarios, the first step may be to contact a specialist for advice about on-going management; e.g., a woman with depression or epilepsy.

For more routine questions there are a number of quick reference resources available which provide useful guidance. Some examples are:

• The New Zealand Formulary (NZF) www.nzformulary.org
• The British National Formulary (BNF) contains a section on use of medicines in pregnancy. While this often re-iterates the manufacturer’s information, it does clearly point out medicines that are known to be teratogenic and those with definitive safety concerns. A useful feature is the description of the trimester(s) of risk and at what stage of pregnancy the medicine will pose the most risk to the foetus.
• Christchurch Drug Information (Clinical Pharmacology) website provides a good overview of the general principles of prescribing in pregnancy. There are also articles on a few specific medicines but the list is not comprehensive.
  www.druginformation.co.nz/pregnancy.htm
• Prescribing Medicines in Pregnancy (Therapeutic Goods Authority � Australia) is a comprehensive resource that assigns a “pregnancy safety category” giving an indication of the relative safety of the medicine based on the available evidence. A copy of the booklet can be downloaded as a pdf and printed. Although the latest edition was published in 1999, a full update is due very soon. The web site includes some updates and amendments to the original publication.
  www.tga.gov.au/DOCS/HTML/mip/medicine.htm

The most up-to-date information should always be sought, especially in the case of newer drugs. Medsafe provides information on current safety concerns and updates to datasheets. This is available from www.medsafe.govt.nz keyword: pregnancy.

Polypharmacy is difficult to apply a standard definition to and various values have been used in the literature, ranging from four to seven or more medicines. A value (i.e. number of concurrent medicines) has often been selected for research purposes so that associations can be made between events (e.g. falls, interactions, hospital admissions) and the “degree” of polypharmacy. This is the context of the statement in the BPJ 26 which described a link between polypharmacy and increased risk of falls. This is an association rather than a causal relationship and does not take into consideration specific regimens which might be perfectly justified.

The statement in the May 2006 polypharmacy POEM was based on a therapeutic view rather than a research or literature based definition. In this context our assertion is that one additional medicine is “polypharmacy” if it is not indicated, no longer required or causes drug-related harm.

The main message is to encourage regular medicines review. This edition of BPJ (BPJ 27) includes an article which provides practical guidance on how to stop unnecessary medicines in older people.