Drug-prescribing challenges during pregnancy

Review

Drug-prescribing challenges during pregnancy
Anette M Freyer

Abstract
Most women take either prescribed or over-the-counter medication during pregnancy. Pregnant women often make independent decisions about their treatment and require careful counselling that allows them to balance the risk of taking a drug against the risk of not taking a drug and leaving a medical conditionuntreated. Advice needs to be tailored to the individual and is hampered by the lack of safety data on drugs in pregnancy and the puerperium. Prescribing is further complicated by both the mother’s and the foetus’ changing physiologies as risk–benefit assessments alter throughout pregnancy. Treatment decisions may require the input of multi-disciplinary teams that consider the severity of the mother’scondition, maternal physiology, a drug’s pharmacokinetic, pharmacodynamic and safety profile and the developmental stage of the foetus.

Keywords concordance; drug safety; pharmacokinetics; pregnancy;
prescribing; teratogen

Introduction
Almost all women use medication at some point during their pregnancy. Around one-third of women receive prescription drugs and many more useover-the-counter preparations. The ubiquitous advice on medicine bottles and package inserts to ‘consult your doctor’ before using the medication should direct a flurry of inquiries to general practitioners, obstetricians and medical specialists. Yet many of us are not well equipped to weigh up the risks and benefits of taking – or not taking – various treatments. There can never be a generic definitive formulaon prescribing for pregnant women (or those that are planning to conceive) but this article will highlight some of the important points to consider.

Challenge 1: preconception counselling
During pregnancy treatment is sought for three separate groups of conditions: pre-existing medical conditions, co-incidental illnesses and pregnancy-induced conditions. Pre-pregnancy counselling has the mostobvious potential benefit in the first instance but should be offered to all women as part of routine medical

care. It is a good opportunity to address the use of medication and supplements in the run up to pregnancy and after conception. It is well recognised that preconception health has an important bearing on pregnancy outcome – a pre-conception visit to offer general health advice and areview of any pre-existing conditions of the mother is, therefore, a good investment. Although there are some general guiding principles, specific advice will depend both on the underlying medical condition as well as the individual circumstances of the prospective mother. The overall aim is for the women to take the lowest effective dose of the least toxic drug for the shortest period to keep hercondition under control and achieve the best possible pregnancy outcome. Not only are women more likely to conceive if their disease is controlled, but they also tend to have fewer flares during pregnancy if they are well controlled when they become pregnant. This is especially true for inflammatory conditions such as inflammatory bowel disease and systemic lupus. Rarely medication will beincreased prior to pregnancy – for the reasons mentioned above or to achieve tight glycaemic control in diabetic patients. Tight diabetic control before and around the time of conception reduces the risk of congenital malformations and warrants intensified insulin regimens. More commonly treatment regimens are reduced – for instance statins for hypercholesterolaemia are usually discontinued andnon-lifesaving medication cut back where possible (e.g. antihistamines for allergic rhinitis, beta-blockers or tricyclic antidepressants for migraine prophylaxis). At other times switching to alternate drug regimens may be advisable (e.g. substituting lamotrigine for sodium valproate in certain forms of epilepsy, changing from an angiotensin-converting enzyme inhibitor to methyldopa in the treatment of...