Effectiveness of Genotype-Specific Tricyclic Antidepressant Dosing in Patients With Major Depressive Disorder: A Randomized Clinical Trial

Optimizing Nortriptyline Dosing: A Comparison between Pharmacogenetics-Based, Phenotype-Based, and Standard Dosing

BACKGROUND AND OBJECTIVE

Nortriptyline, a tricyclic antidepressant, has an important role in the pharmacotherapy of major depressive disorder (MDD). Individualized dosing approaches, such as pharmacogenetics-based and phenotype-based dosing, may enhance early achievement of therapeutic plasma concentrations, but their comparative accuracy has not been investigated. Our objective was to compare the accuracy of three nortriptyline dosing strategies: pharmacogenetics-based, phenotype-based, and standard dosing.

METHODS

Using pharmacokinetic modeling based on data from a randomized controlled trial, we assessed and compared the following dosing strategies: pharmacogenetics-based dosing depending on the cytochrome P-450 (CYP) 2D6 genotype, phenotype-based dosing determined by the plasma concentration measured after a single nortriptyline administration, and standard dosing (125 mg/day). A population pharmacokinetic model was developed to assess phenotype-based dosing recommendations. We evaluated the dosing strategies by comparing the number of participants with predicted therapeutic, subtherapeutic, and supratherapeutic plasma concentrations using Chi-squared (χ2) tests. Variability in plasma concentrations was assessed using F-tests.

RESULTS

Both pharmacogenetics-based (χ2 (1) = 8.0, p = 0.01) and phenotype-based dosing (χ2 (1) = 5.3, p = 0.02) significantly increased the likelihood of achieving therapeutic plasma concentrations compared with standard dosing while reducing plasma concentration variability. No significant difference was found in the prediction of therapeutic concentrations between the two individualized dosing strategies (χ2 (1) = 0.33, p = 0.56).

CONCLUSIONS

Pharmacogenetics-based and phenotype-based dosing demonstrate greater accuracy in predicting therapeutic nortriptyline plasma concentrations than standard dosing. Further research is warranted to explore the clinical application of model-informed precision dosing for nortriptyline and other psychotropic medications.

Impact of using dosing criteria to refine pharmacogenomic clinical decision support for tricyclic antidepressants

PURPOSE

To evaluate the impact of dose-specific logic for tricyclic antidepressant (TCA) pharmacogenomics (PGx) clinical decision support (CDS). We aimed to provide guidance in an area with limited supporting literature, ensure optimal dosing through CDS, and limit alert fatigue. The primary outcome was the reduction in alerts prescribers encountered, while the secondary outcome included an analysis across specialties.

METHODS

A retrospective chart review was conducted to examine TCA PGx CDS before and after implementation of dosing criteria for alerts. Data were abstracted from the electronic medical record. A χ2 test was performed to analyze the frequency of alerts in behavioral health and other specialties.

RESULTS

In the cohort lacking dose criteria, most TCA orders were for indications other than depression (76%) and guidelines would not apply to the majority of these orders. Using dosing criteria to refine CDS reduced the volume of TCA alerts by 74.8%. Alert volume decreased the most in specialties other than behavioral health due to prescriptions for indications other than anxiety or depression (P = 0.035).

CONCLUSION

Dose-centric alerts may be used as a strategy to achieve optimal dosing. Alerting clinicians when dose modifications should occur contributes to getting the right dose to the right patient. Future efforts should focus on optimal dosing of medication through CDS enhancements.

A comparison between rTMS and antidepressant medication on depressive symptom clusters in treatment-resistant depression

BACKGROUND

Antidepressive treatment outcomes can be assessed using sum scores from measurement scales, but symptom clusters may better capture the multidimensional structure of depression. Little is known about the comparative effectiveness of different treatment modalities on these clusters. We sought to evaluate the effects of rTMS and antidepressant medication on four symptom clusters and the extent to which these differ between treatments. In addition, we assessed whether baseline cluster scores predicted (non)response.

METHODS

Data were obtained from two clinical trials (DETECT: rTMS vs. medication; PITA: tricyclic antidepressants). Primary outcomes were symptom cluster scores: 'General Depression', 'Anxiety', 'Somatic Symptoms' and 'Insomnia'. In the primary analysis based on DETECT, a MANCOVA comparing rTMS with medication was performed. For validation, a MANCOVA was performed replacing medication data from DETECT with data from PITA. Baseline symptom cluster scores were compared between responders and non-responders, as well as treatment groups.

RESULTS

In both the primary and validation analyses, no difference was seen between rTMS and medication on the symptom clusters. Similar patterns of response were observed in all groups, with 'Insomnia' showing the greatest effect of treatment. Baseline cluster scores did not predict treatment response.

CONCLUSIONS

We did not find a differential effect of rTMS or antidepressant medication on depressive symptom clusters. Both treatments demonstrated comparable response patterns for all clusters, and baseline cluster scores did not differ between responders and non-responders. Future studies with larger samples or more homogeneous treatments may elucidate the role of symptom clusters as a tool for more individualized treatment.

TRIAL REGISTRATION

PITA NCT03548675 DETECT The Netherlands Trial Register NL7628.

Associations between physical activities and self-harm behaviour in depression across the genotype: findings from the UK biobank

BACKGROUND

Physical activities are widely implemented for non-pharmacological intervention to alleviate depressive symptoms. However, there is little evidence supporting their genotype-specific effectiveness in reducing the risk of self-harm in patients with depression.

AIMS

To assess the associations between physical activity and self-harm behaviour and determine the recommended level of physical activity across the genotypes.

METHOD

We developed the bidirectional analytical model to investigate the genotype-specific effectiveness on UK Biobank. After the genetic stratification of the depression phenotype cohort using hierarchical clustering, multivariable logistic regression models and Cox proportional hazards models were built to investigate the associations between physical activity and the risk of self-harm behaviour.

RESULTS

A total of 28 923 subjects with depression phenotypes were included in the study. In retrospective cohort analysis, the moderate and highly active groups were at lower risk of self-harm behaviour. In the followed prospective cohort analysis, light-intensity physical activity was associated with a lower risk of hospitalisations due to self-harm behaviour in one genetic cluster (adjusted hazard ratio, 0.28 [95% CI, 0.08-0.96]), which was distinguished by three genetic variants: rs1432639, rs4543289 and rs11209948. Compliance with the guideline-level moderate-to-vigorous physical activities was not significantly related to the risk of self-harm behaviour.

CONCLUSIONS

A genotype-specific dose of light-intensity physical activity reduces the risk of self-harm by around a fourth in depressive patients.

Exploring perceived barriers and attitudes in young adults towards antidepressant pharmacotherapy, including the implementation of pharmacogenetic testing to optimize prescription practices

Introduction

The field of pharmacogenetics (PGx) is experiencing significant growth, with increasing evidence to support its application in psychiatric care, suggesting its potential to personalize treatment plans, optimize medication efficacy, and reduce adverse drug reactions. However, the perceived utility and practicability of PGx for psychiatric treatment in youth remains underexplored. This study investigated perceived barriers and attitudes in Australian young adults towards the implementation of PGx testing to guide antidepressant treatment in primary care.

Methods

Semi-structured focus groups and interviews were conducted with 17 participants aged between 18 and 24 years. These sessions were recorded and transcribed before thematic analysis was used to identify collective themes.

Results

Three key themes were identified, including attitudes towards the medication prescription process, concerns and attitudes towards PGx testing, and perceived barriers to its clinical implementation. Although PGx testing was positively perceived by most participants, all participants shared concerns about PGx testing. Participants voiced concerns about the financial impact of PGx testing, the potential for treatment delays, and the accuracy of PGx testing in guiding antidepressant treatment. Additionally, participants noted that the low awareness and willingness of general practitioners to incorporate PGx testing into routine practice could hinder successful clinical implementation.

Discussion

Prior to the implementation of PGx testing into Australian primary practices, it is essential to acknowledge patient perspectives and ensure that clinical practices remain patient-focused. This study highlights important considerations for integrating PGx testing into antidepressant pharmacotherapy and emphasizes the need for future research to address and mitigate the perceived barriers of young adults.

Pharmacogenetics: Opportunities for the All of Us Research Program and Other Large Data Sets to Advance the Field

Pharmacogenetic variation is common and an established driver of response for many drugs. There has been tremendous progress in pharmacogenetics knowledge over the last 30 years and in clinical implementation of that knowledge over the last 15 years. But there have also been many examples where translation has stalled because of the lack of available data sets for discovery or validation research. The recent availability of data from very large cohorts with linked genetic, electronic health record, and other data promises new opportunities to advance pharmacogenetics research. This review presents the stages from pharmacogenetics discovery to widespread clinical adoption using prominent gene-drug pairs that have been implemented into clinical practice as examples. We discuss the opportunities that the All of Us Research Program and other large biorepositories with genomic and linked electronic health record data present in advancing and accelerating the translation of pharmacogenetics into clinical practice.

CYP2C19 Genetic Variants and Major Depressive Disorder: A Systematic Review

Major depressive disorder (MDD) affects over 300 million people globally and has a multifactorial etiology. The CYP2C19 enzyme, involved in metabolizing certain antidepressants, can influence treatment response. Following the PRISMA protocol and PECOS strategy, this systematic review assessed the variation in common CYP2C19 gene variants' frequencies across populations with MDD, evaluating their impact on clinical characteristics and treatment response. We comprehensively searched five databases, identifying 240 articles, of which only nine within the last decade met our inclusion criteria. Except for one study that achieved 74.28% of STROPS items, the rest met at least 75% of GRIPS and STROPS guidelines for quality and bias risk assessment. The CYP2C19's *1 allele, the *1/*1 genotype, and the NM phenotype, considered as references, were generally more frequent. Other CYP2C19 polymorphism frequencies exhibit significant variability across different populations. Some studies associated variants with MDD development, a more extended history of depression, prolonged depressive episodes, and symptom severity, while others reported no such association. Some studies confirmed variants' effects on escitalopram and citalopram metabolism but not that of other drugs, such as sertraline, venlafaxine, and bupropion. Treatment tolerability and symptom improvement also varied between studies. Despite some common findings, inconsistencies highlight the need for further research to clarify the role of these polymorphisms in MDD and optimize treatment strategies.

rTMS as a Next Step in Antidepressant Nonresponders: A Randomized Comparison With Current Antidepressant Treatment Approaches

OBJECTIVE

Although repetitive transcranial magnetic stimulation (rTMS) is an effective treatment for depression, little is known about the comparative effectiveness of rTMS and other treatment options, such as antidepressants. In this multicenter randomized controlled trial, rTMS was compared with the next pharmacological treatment step in patients with treatment-resistant depression.

METHODS

Patients with unipolar nonpsychotic depression (N=89) with an inadequate response to at least two treatment trials were randomized to treatment with rTMS or to a switch of antidepressants, both in combination with psychotherapy. Treatment duration was 8 weeks and consisted of either 25 high-frequency rTMS sessions to the left dorsolateral prefrontal cortex or a switch of antidepressant medication following the Dutch treatment algorithm. The primary outcome was change in depression severity based on the Hamilton Depression Rating Scale (HAM-D). Secondary outcomes were response and remission rates as well as change in symptom dimensions (anhedonia, anxiety, sleep, rumination, and cognitive reactivity). Finally, expectations regarding treatment were assessed.

RESULTS

rTMS resulted in a significantly larger reduction in depressive symptoms than medication, which was also reflected in higher response (37.5% vs. 14.6%) and remission (27.1% vs. 4.9%) rates. A larger decrease in symptoms of anxiety and anhedonia was observed after rTMS compared with a switch in antidepressants, and no difference from the medication group was seen for symptom reductions in rumination, cognitive reactivity, and sleep disorders. Expectations regarding treatment correlated with changes in HAM-D scores.

CONCLUSIONS

In a sample of patients with moderately treatment-resistant depression, rTMS was more effective in reducing depressive symptoms than a switch of antidepressant medication. In addition, the findings suggest that the choice of treatment may be guided by specific symptom dimensions.

Association of CYP2D6 and CYP2C19 metabolizer status with switching and discontinuing antidepressant drugs: an exploratory study

BACKGROUND

Tailoring antidepressant drugs (AD) to patients' genetic drug-metabolism profile is promising. However, literature regarding associations of ADs' treatment effect and/or side effects with drug metabolizing genes CYP2D6 and CYP2C19 has yielded inconsistent results. Therefore, our aim was to longitudinally investigate associations between CYP2D6 (poor, intermediate, and normal) and CYP2C19 (poor, intermediate, normal, and ultrarapid) metabolizer-status, and switching/discontinuing of ADs. Next, we investigated whether the number of perceived side effects differed between metabolizer statuses.

METHODS

Data came from the multi-site naturalistic longitudinal cohort Netherlands Study of Depression and Anxiety (NESDA). We selected depression- and/or anxiety patients, who used AD at some point in the course of the 9 years follow-up period (n = 928). Medication use was followed to assess patterns of AD switching/discontinuation over time. CYP2D6 and CYP2C19 alleles were derived using genome-wide data of the NESDA samples and haplotype data from the PharmGKB database. Logistic regression analyses were conducted to investigate the association of metabolizer status with switching/discontinuing ADs. Mann-Whitney U-tests were conducted to compare the number of patient-perceived side effects between metabolizer statuses.

RESULTS

No significant associations were observed of CYP metabolizer status with switching/discontinuing ADs, nor with the number of perceived side effects.

CONCLUSIONS

We found no evidence for associations between CYP metabolizer statuses and switching/discontinuing AD, nor with side effects of ADs, suggesting that metabolizer status only plays a limited role in switching/discontinuing ADs. Additional studies with larger numbers of PM and UM patients are needed to further determine the potential added value of pharmacogenetics to guide pharmacotherapy.

Drug-Gene Risk Stratification in Patients with Suspected Drug-Induced Interstitial Lung Disease

BACKGROUND

Pulmonary toxicity has been associated with drug use. This is often not recognized in clinical practice, and underestimated.

OBJECTIVE

We aimed to establish whether polymorphisms in certain genes corresponding with a metabolic pathway of drug(s) used are associated with pulmonary toxicity in patients with suspected drug-induced interstitial lung disease (DI-ILD).

METHODS

This retrospective observational study explored genetic variations in three clinically relevant cytochrome P450 (CYP) iso-enzymes (i.e., CYP2D6, CYP2C9, and CYP2C19) in a group of patients with a fibroticinterstitial lung disease, either non-specific interstitial pneumonia (n = 211) or idiopathic pulmonary fibrosis (n = 256), with a suspected drug-induced origin.

RESULTS

Of the 467 patients, 79.0% showed one or more polymorphisms in the tested genes accompanied by the use of drug(s) metabolized by a corresponding affected metabolic pathway (60.0% poor metabolizers and/or using two or more drugs [likely DI-ILD], 37.5% using three or more [highly likely DI-ILD]). Most commonly used drugs were statins (63.1%) with a predominance among men (69.4 vs 47.1%, p < 0.0001). Nitrofurantoin, not metabolized by the tested pathways, was prescribed more frequently among women (51.9 vs 4.5%, p < 0.00001).

CONCLUSIONS

In our cohort with suspected DI-ILD, 79% carried one or more genetic variants accompanied by the use of drugs metabolized by a corresponding affected pathway. In 60%, the diagnosis of DI-ILD was likely, whereas in 37.5%, it was highly likely, based on CYP analyses. This study underlines the importance of considering both drug use and genetic make-up as a possible cause, or at least a contributing factor, in the development and/or progression of fibrotic lung diseases.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT00267800, registered in 2005.

Current level of evidence for improvement of antidepressant efficacy and tolerability by pharmacogenomic-guided treatment: A Systematic review and meta-analysis of randomized controlled clinical trials

The aim of the study was to assess the clinical utility of currently available pharmacogenomic (PGx) tools compared with treatment as usual (TAU), using a meta-analysis of dichotomous and continuous antidepressant efficacy and tolerability data from previously published clinical trials. MEDLINE, clinicaltrial.gov, EU Clinical Trials Register, WHO ICTRP and CENTRAL were systematically searched; of the 962 results originally reviewed, 15 trials were included. Antidepressant efficacy was quantified by relative and absolute changes in symptom severity after eight weeks of treatment and by response and remission rates, while tolerability was estimated by the rate of study discontinuation for any reason. In the PGx-guided patients, symptom severity reduced by an average of 31.0% after eight weeks of treatment, compared to an average reduction of 26.8% in the TAU group. Accordingly, PGx-guided patients experienced a greater reduction in symptom severity of 3.4% (95%CI: 1.6-5.3%), which corresponded to a reduction in the Hamilton Depression score of 0.75 (0.30-1.21), a 37% (15-63%) higher remission rate, and an 18% (5-33%) higher response rate compared with TAU patients, while no difference was observed in discontinuation rate between groups. Notably, the majority of associations lost statistical significance when restricting the dataset to low risk of bias studies, while certain funnel plots suggested a potential publication bias favoring the reporting of statistically significant results. In summary, PGx tools marginally enhance antidepressant efficacy, but not antidepressant tolerability; thus, additional research and advancement of PGx tools are needed to improve integration of PGx in clinical pharmacotherapy of depression.

A review of real-world evidence on preemptive pharmacogenomic testing for preventing adverse drug reactions: a reality for future health care

Adverse drug reactions (ADRs) are a significant public health concern and a leading cause of hospitalization; they are estimated to be the fourth leading cause of death and increasing healthcare costs worldwide. Carrying a genetic variant could alter the efficacy and increase the risk of ADRs associated with a drug in a target population for commonly prescribed drugs. The use of pre-emptive pharmacogenetic/omic (PGx) testing can improve drug therapeutic efficacy, safety, and compliance by guiding the selection of drugs and/or dosages. In the present narrative review, we examined the current evidence of pre-emptive PGx testing-based treatment for the prevention of ADRs incidence and hospitalization or emergency department visits due to serious ADRs, thus improving patient safety. We then shared our perspective on the importance of preemptive PGx testing in clinical practice for the safe use of medicines and decreasing healthcare costs.

A New Intervention for Implementation of Pharmacogenetics in Psychiatry: A Description of the PSY-PGx Clinical Study

(1) Background Pharmacological treatment for psychiatric disorders has shown to only be effective in about one-third of patients, as it is associated with frequent treatment failure, often because of side effects, and a long process of trial-and-error pharmacotherapy until an effective and tolerable treatment is found. This notion emphasizes the urgency for a personalized medicine approach in psychiatry. (2) Methods This prospective patient- and rater-blinded, randomized, controlled study will investigate the effect of dose-adjustment of antidepressants escitalopram and sertraline or antipsychotics risperidone and aripiprazole according to the latest state-of-the-art international dosing recommendations for CYP2C19 and CYP2D6 metabolizer status in patients with mood, anxiety, and psychotic disorders. A total sample of N = 2500 will be recruited at nine sites in seven countries (expected drop-out rate of 30%). Patients will be randomized to a pharmacogenetic group or a dosing-as-usual group and treated over a 24-week period with four study visits. The primary outcome is personal recovery using the Recovery Assessment Scale as assessed by the patient (RAS-DS), with secondary outcomes including clinical effects (response or symptomatic remission), side effects, general well-being, digital phenotyping, and psychosocial functioning. (3) Conclusions This is, to our knowledge, the first international, multi-center, non-industry-sponsored randomized controlled trial (RCT) that may provide insights into the effectiveness and utility of implementing pharmacogenetic-guided treatment of psychiatric disorders, and as such, results will be incorporated in already available dosing guidelines.

Pharmacogenomics in clinical trials: an overview

With the trend towards promoting personalised medicine (PM), the application of pharmacogenetics and pharmacogenomics (PGx) is of growing importance. For the purposes of clinical trials, the inclusion of PGx is an additional tool that should be considered for improving our knowledge about the effectiveness and safety of new drugs. A search of available clinical trials containing pharmacogenetic and PGx information was conducted on ClinicalTrials.gov. The results show there has been an increase in the number of trials containing PGx information since the 2000 s, with particular relevance in the areas of Oncology (28.43%) and Mental Health (10.66%). Most of the clinical trials focus on treatment as their primary purpose. In those clinical trials entries where the specific genes considered for study are detailed, the most frequently explored genes are CYP2D6 (especially in Mental Health and Pain), CYP2C9 (in Hematology), CYP2C19 (in Cardiology and Mental Health) and ABCB1 and CYP3A5 (particularly prominent in Transplantation and Cardiology), among others. Researchers and clinicans should be trained in pharmacogenetics and PGx in order to be able to make a proper interpretation of this data, contributing to better prescribing decisions and an improvement in patients' care, which would lead to the performance of PM.

CYP2D6 and CYP2C19 Variant Coverage of Commercial Antidepressant Pharmacogenomic Testing Panels Available in Victoria, Australia

Pharmacogenomic (PGx) testing to inform antidepressant medication selection and dosing is gaining attention from healthcare professionals, patients, and payors in Australia. However, there is often uncertainty regarding which test is most suitable for a particular patient. Here, we identified and evaluated the coverage of CYP2D6 and CYP2C19 variants in commercial antidepressant PGx testing panels in Victoria, a large and ethnically diverse state of Australia. Test characteristics and star alleles tested for both genes were obtained directly from pathology laboratories offering PGx testing and compared against the Association of Molecular Pathology's recommended minimum (Tier 1) and extended (Tier 2) allele sets. Although all tests covered the minimum recommended alleles for CYP2C19, this was not the case for CYP2D6. This study emphasizes that PGx tests might not be suitable for all individuals in Australia due to the limited range of star alleles assessed. Inadequate haplotype coverage may risk misclassification of an individual's predicted metabolizer phenotype, which has ramifications for depression medication selection and dosage. This study underscores the urgent need for greater standardization in PGx testing and emphasizes the importance of considering genetic ancestry when choosing a PGx testing panel to ensure optimal clinical applicability.

Utility of pharmacogenetic testing to optimise antidepressant pharmacotherapy in youth: a narrative literature review

Pharmacogenetics (PGx) is the study and application of how interindividual differences in our genomes can influence drug responses. By evaluating individuals' genetic variability in genes related to drug metabolism, PGx testing has the capabilities to individualise primary care and build a safer drug prescription model than the current "one-size-fits-all" approach. In particular, the use of PGx testing in psychiatry has shown promising evidence in improving drug efficacy as well as reducing toxicity and adverse drug reactions. Despite randomised controlled trials demonstrating an evidence base for its use, there are still numerous barriers impeding its implementation. This review paper will discuss the management of mental health conditions with PGx-guided treatment with a strong focus on youth mental illness. PGx testing in clinical practice, the concerns for its implementation in youth psychiatry, and some of the barriers inhibiting its integration in clinical healthcare will also be discussed. Overall, this paper provides a comprehensive review of the current state of knowledge and application for PGx in psychiatry and summarises the capabilities of genetic information to personalising medicine for the treatment of mental ill-health in youth.

Frequencies of Combined Dysfunction of Cytochromes P450 2C9, 2C19, and 2D6 in an Italian Cohort: Suggestions for a More Appropriate Medication Prescribing Process

Improper drug prescription is a main cause of both drug-related harms (inefficacy and toxicity) and ineffective spending and waste of the healthcare system's resources. Nowadays, strategies to support an improved, informed prescription process may benefit from the adequate use of pharmacogenomic testing. Using next-generation sequencing, we analyzed the genomic profile for three major cytochromes P450 (CYP2C9, CYP2C19, CYP2D6) and studied the frequencies of dysfunctional isozymes (e.g., poor, intermediate, or rapid/ultra-rapid metabolizers) in a cohort of 298 Italian subjects. We found just 14.8% of subjects with a fully normal set of cytochromes, whereas 26.5% of subjects had combined cytochrome dysfunction (more than one isozyme involved). As improper drug prescription is more frequent, and more burdening, in polytreated patients, since drug-drug interactions also cause patient harm, we discuss the potential benefits of a more comprehensive PGX testing approach to support informed drug selection in such patients.

Pharmacogenomics and the Management of Mood Disorders-A Review

Due to the chronic relapsing nature of mental disorders and increased life expectancy, the societal burden of these non-communicable diseases will increase even further. Treatments for mental disorders, such as depression, are available, but their effect is limited due to patients' (genetic) heterogeneity, low treatment compliance and frequent side effects. In general, only one-third of the patients respond to treatment. Today, medication selection in psychiatry relies on a trial-and-error approach based mainly on physicians' experience. Pharmacogenetic (PGx) testing can help in this process by determining the person-specific genetic factors that may predict clinical response and side effects associated with genetic variants that impact drug-metabolizing enzymes, drug transporters or drug targets. PGxis a discipline that investigates genetic factors that affect the absorption, metabolism, and transport of drugs, thereby affecting therapy outcome. These genetic factors can, among other things, lead to differences in the activity of enzymes that metabolize drugs. Studies in depressed patients show that genotyping of drug-metabolizing enzymes can increase the effectiveness of treatment, which could benefit millions of patients worldwide. This review highlights these studies, gives recommendations and provides future perspectives on how to proceed with PGx testing. Finally, it is recommended to consider genotyping for CYP2D6 and CYP2C19, when there is an indication (side effects or inefficacy).