The purpose of this study is to assess the clinical impact of reducing treatment failure rates after using genetic information targeting CYP2C19 in validating escitalopram prescription. 5 pharmacies in the canton of Vaud (Lausanne, Switzerland) will participate in the study.

The study will also explored the ability to perform the test in community pharmacy, physician and pharmacist approval of prescription changes, patient acceptance of the test and dose changes, the economic impact of the test, the association between genetic polymorphisms and therapeutic failures and the degree of satisfaction, barriers and facilitators by stakeholders.

Response to medication depends on many clinical, demographic, environmental, and genetic factors. Non-genetic factors that are often considered when prescribing treatments address not only drug-drug interactions, but also the patient's environment, comorbidities, gender, and age. Genetic factors, which are not commonly considered during prescribing except for some drugs, account for 15-30% of the variability in drug response. From a pharmacokinetic point of view, genetic polymorphisms are likely to modify drug absorption, metabolism, transport and elimination. Data from the literature indicate that the concentration profiles of many drugs are genetically influenced. It is also well known that genetic polymorphisms that alter the targeting of some drugs can alter drug response, especially in oncology.

Personalization of medicine is a fundamental approach to treating patients individually. Pilot studies to integrate pharmacogenetics into practice are already being conducted in hospitals, and some pharmacies abroad offer pharmacogenetic testing, as in Canada and Germany.

In Switzerland, a new Ordinance on Genetic Analysis Act was passed on September 23, 2022, allowing pharmacists to carry out genetic testing in the medical field.Because of the increasing evidence of the influence of CYP2C19 genetic polymorphisms on the efficacy and toxicity of escitalopram, the high prevalence of prescription of this drug in the treatment of depression, the prevalence of genetic polymorphisms in the Caucasian population (30% ultra-rapid metabolizers and 4% poor metabolizers) and the potential costs to public health, this drug was chosen as a prototype for this pilot project.

Therefore, investigators want to conduct a pilot study to evaluate the efficacy, safety, feasibility, and cost-effectiveness of pharmacy-based genetic testing as part of patient care management and identified barriers to using such tests.

Inclusion Criteria:

• Must consent to participate in the study,
• Must sign consent,
• Must be able to follow and understand the study procedures,
• Initiation of escitalopram treatment for unipolar depression with or without anxiety

Exclusion Criteria:

• Other condition than depression (such as panic disorder)
• Escitalopram treatment already received
• Not able to consent to participate in the study.

Patients in each group will be blinded, as CYP2C19 genetic information is not given until the study is completed.