Pharmacogenetics
Ethical issues in treatment and clinical practice
Introduction
5.1 In this chapter, we consider ethical issues raised by the use of pharmacogenetic tests and medicines in clinical practice and examine the implications of pharmacogenetics for the individual patients and their physicians. There are currently relatively few clinical applications of pharmacogenetics. Moreover, it is important to realise that the discovery of genetic factors that influence response to medicines may not equate with direct or immediate changes in clinical practice, since the factors influencing the efficacy and safety of medicines are varied and complex, and since the use of pharmacogenetic tests may not necessarily be cost-effective or clinically useful.
5.2 Notwithstanding these caveats, there will be situations in which pharmacogenetic tests provide information of considerable clinical value. The medicine Herceptin (Box 2.3: Case study 2) and the test used in patients with acute lymphoblastic leukaemia who are to be treated with 6-mercaptopurine (paragraph 4.5) are two good examples. Herceptin has been licensed in the UK for use only in patients with the relevant type of tumour, which means that tests must be undertaken to determine the genetic characteristics of the disease before the medicine can be prescribed.1 There are various other medicines which are metabolised by cytochrome P450 enzymes which contain warnings regarding potential adverse reactions in patients with particular variants of these enzymes (such as variants in CYP2D6 - see Box 2.2: Case study 1). However, there is no requirement in the licence conditions of these medicines for patients to undertake a pharmacogenetic test before prescription. Preliminary findings, such as the research into adverse reactions in response to abacavir (Box 2.4: Case study 3), have not been transferred to clinical practice in most countries, as further research is still taking place
Footnotes1 British National Formulary (2002) BNF, 44 ed (London: British Medical Association and the Royal Pharmaceutical Society of Great Britain).