Despite initial enthusiasm, the use of pharmacogenetics has remained limited to investigation in only a few clinical fields such as oncology and psychiatry. The main reason is the paucity of scientific evidence to show that pharmacogenetic testing leads to improved clinical outcomes. 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. 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.

In carriers of the CYP2C9*3 allele more difficulties in terms of stabilization and overanticoagulation were found as compared with wild-type subjects or CYP2C9*2 carriers. CYP2C9 genotyping could be useful to identify potential candidates for more frequent INR controls to minimize problems with acenocoumarol anticoagulation status.

The advanced CDSS produced a higher proportion of clinically relevant medication alerts, but the number of irrelevant alerts remained high. To improve the PPV of the advanced CDSS, the algorithms should be optimized by identifying additional risk modifiers and more data should be made electronically available to improve the performance of the algorithms. Our study illustrates and corroborates the need for cyclic testing of technical improvements in information technology in circumstances representative of daily clinical practice.

The presence of at least 1 CYP2C9*2 or *3 allele in phenprocoumon users is associated with an increased risk of severe overanticoagulation. Similar to warfarin and acenocoumarol, phenprocoumon had a lower dosage requirement in carriers of CYP2C9*2 or *3 compared with that in CYP2C9 wild-type subjects.

6 cases of contact allergy to the antitumor antibiotic mitomycin C from intravesical instillation are described. Reports suggest that up to 9% of patients treated with mitomycin C for chemoresection/prevention of superficial bladder cancer will develop cutaneous side-effects. Patients may present either with vesicular dermatitis of the hands and feet and/or dermatitis of the genitals, or with more widespread eruptions. Probably most, if not all, skin reactions are caused by contact allergy. The distribution is suggestive of systemic contact dermatitis from mitomycin C absorbed from the vesical mucosa.