1. ¹Department of Clinical Pharmacy and Toxicology, Leiden University Medical Center, Leiden, The Netherlands
2. ²Department of Clinical Pharmacy, University Medical Center Utrecht, Utrecht, The Netherlands
3. ³Division of Pharmacoepidemiology and Pharmacotherapy, Utrecht Institute for Pharmaceutical Sciences (UIPS), Faculty of Science, Utrecht University, Utrecht, The Netherlands
4. ⁴Division of Drug Information Centre, Koninklijke Nederlandse Maatschappij ter bevordering der Pharmacie, The Hague, The Netherlands
5. ⁵Department of Clinical Pharmacy, Wilhelmina Hospital Assen, Assen, The Netherlands
6. ⁶Central Hospital Pharmacy, The Hague, The Netherlands
7. ⁷Laboratory for Pharmacology and Toxicology, Hospital Pharmacy Noordoost-Brabant, 's-Hertogenbosch, The Netherlands
8. ⁸Department of Internal Medicine, University Hospital Maastricht, Maastricht, The Netherlands
9. ⁹Department of Clinical Chemistry, St. Jansdal Hospital, Harderwijk, The Netherlands
10. ¹⁰Department of Pharmacotherapy and Pharmaceutical care, GUIDE, University of Groningen, Groningen, The Netherlands
11. ¹¹Department of Clinical Pharmacy, Zorggroep Noorderbreedte and De Tjongerschans, Leeuwarden, The Netherlands
12. ¹²Department of Clinical Pharmacy, St. Antonius Hospital, Nieuwegein, The Netherlands

Correspondence: H.-J. Guchelaar, (h.j.guchelaar@lumc.nl)

Received 30 October 2007; Accepted 13 December 2007; Published online 6 February 2008.

Abstract

Despite initial enthusiasm,^1,2,3 the use of pharmacogenetics has remained limited to investigation in only a few clinical fields such as oncology and psychiatry.^4,5,6,7,8 The main reason is the paucity of scientific evidence to show that pharmacogenetic testing leads to improved clinical outcomes.^9,10 Moreover, for most pharmacogenetic tests (such as tests for genetic variants of cytochrome P450 enzymes) a detailed knowledge of pharmacology is a prerequisite for application in clinical practice, and both physicians and pharmacists might find it difficult to interpret the clinical value of pharmacogenetic test results. Guidelines that link the result of a pharmacogenetic test to therapeutic recommendations might help to overcome these problems, but such guidelines are only sparsely available. In 2001, an early step was taken to develop such guidelines for the therapeutic use of antidepressants, and these included CYP2D6-related dose recommendations drawn from pharmacokinetic study data.¹¹ However, the use of such recommendations in routine clinical practice remains difficult, because they are currently outside the ambit of the clinical environment and are not accessible during the decision-making process by physicians and pharmacists, namely the prescription and dispensing of drugs.