In clinical practice, there is a need for a more individualized selection of antidepressants and adequate dosage. The investigation of pharmacokinetically relevant genes is a promising approach to assist this selection. In the past 2 years, two commercially available tests have been subject of advertisement, a test from Stada, which analyses variants of the cytochrome P450 isoenzymes CYP2D6 and CYP2C19 and a test from HMNC Brain Health, which analyses variants of the ABCB1 gene. The costs for both kits are not covered by the statutory health insurance and it is therefore proposed that the patients are invoiced directly in the form of individual healthcare payment. The companies claim that by applying the tests antidepressant treatment failure can be avoided and that patients will respond faster to the antidepressant used. These claims are not based on appropriate clinical trials, which are either lacking or reveal conflicting results. Hence, the routine use of these tests is not recommended. In accordance with the German S3 Guideline for unipolar depression, therapeutic drug monitoring (TDM) of serum levels should be carried out in cases of non-response to an antidepressant with adequate dosage and duration. As a rule the costs for TDM are covered by the statutory health insurance. Cytochrome P450 genotyping is only indicated when the serum level is not within the expected range and other reasons to explain this discrepancy are excluded. Many laboratories provide these analyses and in individual cases the costs are reimbursed by the statutory health insurance. Further research should be carried out to investigate the importance of the ABCB1 gene for the treatment with antidepressants.
Keywords: ABCB1 gene; Cytochrome P450; Non-response; Pharmacogenetics; Therapeutic drug monitoring.