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The Dutch Pharmacogenetics Working Group (DPWG) aims to facilitate pharmacogenetics implementation in clinical practice by developing evidence-based guidelines to optimize pharmacotherapy. A guideline describing the gene-drug interaction between the genes CYP2D6, CYP3A4 and CYP1A2 and antipsychotics is presented here. The DPWG identified gene-drug interactions that require therapy adjustments when respective genotype is known for CYP2D6 with aripiprazole, brexpiprazole, haloperidol, pimozide, risperidone and zuclopenthixol, and for CYP3A4 with quetiapine. Evidence-based dose recommendations were obtained based on a systematic review of published literature. Reduction of the normal dose is recommended for aripiprazole, brexpiprazole, haloperidol, pimozide, risperidone and zuclopenthixol for CYP2D6-predicted PMs, and for pimozide and zuclopenthixol also for CYP2D6 IMs. For CYP2D6 UMs, a dose increase or an alternative drug is recommended for haloperidol and an alternative drug or titration of the dose for risperidone. In addition, in case of no or limited clinical effect, a dose increase is recommended for zuclopenthixol for CYP2D6 UMs. Even though evidence is limited, the DPWG recommends choosing an alternative drug to treat symptoms of depression or a dose reduction for other indications for quetiapine and CYP3A4 PMs. No therapy adjustments are recommended for the other CYP2D6 and CYP3A4 predicted phenotypes. In addition, no action is required for the gene-drug combinations CYP2D6 and clozapine, flupentixol, olanzapine or quetiapine and also not for CYP1A2 and clozapine or olanzapine. For identified gene-drug interactions requiring therapy adjustments, genotyping of CYP2D6 or CYP3A4 prior to treatment should not be considered for all patients, but on an individual patient basis only.

Pharmacogenetics (PGx) studies the effect of heritable genetic variation on drug response. Clinical adoption of PGx has remained limited, despite progress in the field. To promote implementation, the Dutch Pharmacogenetics Working Group (DPWG) develops evidence-based guidelines on how to optimize pharmacotherapy based on PGx test results. This guideline describes optimization of atomoxetine therapy based on genetic variation in the CYP2D6 gene. The CYP2D6 enzyme is involved in conversion of atomoxetine into the metabolite 4-hydroxyatomoxetine. With decreasing CYP2D6 enzyme activity, the exposure to atomoxetine and the risk of atomoxetine induced side effects increases. So, for patients with genetically absent CYP2D6 enzyme activity (CYP2D6 poor metabolisers), the DPWG recommends to start with the normal initial dose, bearing in mind that increasing this dose probably will not be required. In case of side effects and/or a late response, the DPWG recommends to reduce the dose and check for sustained effectiveness for both poor metabolisers and patients with genetically reduced CYP2D6 enzyme activity (CYP2D6 intermediate metabolisers). Extra vigilance for ineffectiveness is required in patients with genetically increased CYP2D6 enzyme activity (CYP2D6 ultra-rapid metabolisers). No interaction was found between the CYP2D6 and COMT genes and methylphenidate. In addition, no interaction was found between CYP2D6 and clonidine, confirming the suitability of clonidine as a possible alternative for atomoxetine in variant CYP2D6 metabolisers. The DPWG classifies CYP2D6 genotyping as being "potentially beneficial " for atomoxetine. CYP2D6 testing prior to treatment can be considered on an individual patient basis.

The Dutch Pharmacogenetics Working Group (DPWG) aims to facilitate PGx implementation by developing evidence-based pharmacogenetics guidelines to optimize pharmacotherapy. This guideline describes the starting dose optimization of the anti-cancer drug irinotecan to decrease the risk of severe toxicity, such as (febrile) neutropenia or diarrhoea. Uridine diphosphate glucuronosyl transferase 1A1 (UGT1A1 encoded by the UGT1A1 gene) enzyme deficiency increases risk of irinotecan-induced toxicity. Gene variants leading to UGT1A1 enzyme deficiency (e.g. UGT1A1*6, *28 and *37) can be used to optimize an individual's starting dose thereby preventing carriers from toxicity. Homozygous or compound heterozygous carriers of these allele variants are defined as UGT1A1 poor metabolisers (PM). DPWG recommends a 70% starting dose in PM patients and no dose reduction in IM patients who start treatment with irinotecan. Based on the DPWG clinical implication score, UGT1A1 genotyping is considered "essential", indicating that UGT1A1 testing must be performed prior to initiating irinotecan treatment.

Pharmacogenetics (PGx) studies the effect of heritable genetic variation on drug response. Clinical adoption of PGx has remained limited, despite progress in the field. To promote implementation, the Dutch Pharmacogenetics Working Group (DPWG) develops evidence-based guidelines on how to optimize pharmacotherapy based on PGx test results. This guideline describes optimization of atomoxetine therapy based on genetic variation in the CYP2D6 gene. The CYP2D6 enzyme is involved in conversion of atomoxetine into the metabolite 4-hydroxyatomoxetine. With decreasing CYP2D6 enzyme activity, the exposure to atomoxetine and the risk of atomoxetine induced side effects increases. So, for patients with genetically absent CYP2D6 enzyme activity (CYP2D6 poor metabolisers), the DPWG recommends to start with the normal initial dose, bearing in mind that increasing this dose probably will not be required. In case of side effects and/or a late response, the DPWG recommends to reduce the dose and check for sustained effectiveness for both poor metabolisers and patients with genetically reduced CYP2D6 enzyme activity (CYP2D6 intermediate metabolisers). Extra vigilance for ineffectiveness is required in patients with genetically increased CYP2D6 enzyme activity (CYP2D6 ultra-rapid metabolisers). No interaction was found between the CYP2D6 and COMT genes and methylphenidate. In addition, no interaction was found between CYP2D6 and clonidine, confirming the suitability of clonidine as a possible alternative for atomoxetine in variant CYP2D6 metabolisers. The DPWG classifies CYP2D6 genotyping as being "potentially beneficial" for atomoxetine. CYP2D6 testing prior to treatment can be considered on an individual patient basis.

The Dutch Pharmacogenetics Working Group (DPWG) aims to facilitate PGx implementation by developing evidence-based pharmacogenetics guidelines to optimize pharmacotherapy. This guideline describes the gene-drug interaction of ABCG2 with allopurinol, HLA-B with allopurinol, MTHFR with folic acid, and MTHFR with methotrexate, relevant for the treatment of gout, cancer, and rheumatoid arthritis. A systematic review was performed based on which pharmacotherapeutic recommendations were developed. Allopurinol is less effective in patients with the ABCG2 p.(Gln141Lys) variant. In HLA-B*58:01 carriers, the risk of severe cutaneous adverse events associated with allopurinol is strongly increased. The DPWG recommends using a higher allopurinol dose in patients with the ABCG2 p.(Gln141Lys) variant. For HLA-B*58:01 positive patients the DPWG recommends choosing an alternative (for instance febuxostat). The DPWG indicates that another option would be to precede treatment with allopurinol tolerance induction. Genotyping of ABCG2 in patients starting on allopurinol was judged to be 'potentially beneficial' for drug effectiveness, meaning genotyping can be considered on an individual patient basis. Genotyping for HLA-B*58:01 in patients starting on allopurinol was judged to be 'beneficial' for drug safety, meaning it is advised to consider genotyping the patient before (or directly after) drug therapy has been initiated. For MTHFR-folic acid there is evidence for a gene-drug interaction, but there is insufficient evidence for a clinical effect that makes therapy adjustment useful. Finally, for MTHFR-methotrexate there is insufficient evidence for a gene-drug interaction.

The Dutch Pharmacogenetics Working Group (DPWG) aims to facilitate PGx implementation by developing evidence-based pharmacogenetics guidelines to optimize pharmacotherapy. This guideline describes the starting dose optimization of the anti-cancer drug irinotecan to decrease the risk of severe toxicity, such as (febrile) neutropenia or diarrhoea. Uridine diphosphate glucuronosyl transferase 1A1 (UGT1A1 encoded by the UGT1A1 gene) enzyme deficiency increases risk of irinotecan-induced toxicity. Gene variants leading to UGT1A1 enzyme deficiency (e.g. UGT1A1*6, *28 and *37) can be used to optimize an individual's starting dose thereby preventing carriers from toxicity. Homozygous or compound heterozygous carriers of these allele variants are defined as UGT1A1 poor metabolisers (PM). DPWG recommends a 70% starting dose in PM patients and no dose reduction in IM patients who start treatment with irinotecan. Based on the DPWG clinical implication score, UGT1A1 genotyping is considered "essential", indicating that UGT1A1 testing must be performed prior to initiating irinotecan treatment.

Contains fulltext : 286842.pdf (Publisher’s version ) (Closed access) The Dutch Pharmacogenetics Working Group (DPWG) guideline presented here, presents the gene-drug interaction between the genes CYP2C19 and CYP2D6 and antidepressants of the selective serotonin reuptake inhibitor type (SSRIs). Both genes' genotypes are translated into predicted normal metabolizer (NM), intermediate metabolizer (IM), poor metabolizer (PM), or ultra-rapid metabolizer (UM). Evidence-based dose recommendations were obtained, based on a structured analysis of published literature. In CYP2C19 PM patients, escitalopram dose should not exceed 50% of the normal maximum dose. In CYP2C19 IM patients, this is 75% of the normal maximum dose. Escitalopram should be avoided in UM patients. In CYP2C19 PM patients, citalopram dose should not exceed 50% of the normal maximum dose. In CYP2C19 IM patients, this is 70% (65-75%) of the normal maximum dose. In contrast to escitalopram, no action is needed for CYP2C19 UM patients. In CYP2C19 PM patients, sertraline dose should not exceed 37.5% of the normal maximum dose. No action is needed for CYP2C19 IM and UM patients. In CYP2D6 UM patients, paroxetine should be avoided. No action is needed for CYP2D6 PM and IM patients. In addition, no action is needed for the other gene-drug combinations. Clinical effects (increase in adverse events or decrease in efficacy) were lacking for these other gene-drug combinations. DPWG classifies CYP2C19 genotyping before the start of escitalopram, citalopram, and sertraline, and CYP2D6 genotyping before the start of paroxetine as "potentially beneficial" for toxicity/effectivity predictions. This indicates that genotyping prior to treatment can be considered on an individual patient basis.

The current Dutch Pharmacogenetics Working Group (DPWG) guideline, describes the gene-drug interaction between CYP2D6 and the opioids codeine, tramadol and oxycodone. CYP2D6 genotype is translated into normal metaboliser (NM), intermediate metaboliser (IM), poor metaboliser (PM) or ultra-rapid metaboliser (UM). Codeine is contraindicated in UM adults if doses20 mg every 6 h (q6h), in children ≥12 years if doses10 mg q6h, or with additional risk factors. In PMs, an alternative analgesic should be given which is not or to a lesser extent metabolised by CYP2D6 (not tramadol). In IMs with insufficient analgesia, a higher dose or alternative analgesic should be given. For tramadol, the recommendations for IMs and PMs are the same as the recommendation for codeine and IMs. UMs should receive an alternative drug not or to a lesser extent metabolised by CYP2D6 or the dose should be decreased to 40% of the commonly prescribed dose. Due to the absence of effect on clinical outcomes of oxycodone in PMs, IMs and UMs no action is required. DPWG classifies CYP2D6 genotyping for codeine "beneficial" and recommends testing prior to, or shortly after initiation of treatment in case of higher doses or additional risk factors. CYP2D6 genotyping is classified as "potentially beneficial" for tramadol and can be considered on an individual patient basis.

Contains fulltext : 286843.pdf (Publisher’s version ) (Closed access) The current Dutch Pharmacogenetics Working Group (DPWG) guideline, describes the gene-drug interaction between CYP2D6 and the opioids codeine, tramadol and oxycodone. CYP2D6 genotype is translated into normal metaboliser (NM), intermediate metaboliser (IM), poor metaboliser (PM) or ultra-rapid metaboliser (UM). Codeine is contraindicated in UM adults if doses >20 mg every 6 h (q6h), in children ≥12 years if doses >10 mg q6h, or with additional risk factors. In PMs, an alternative analgesic should be given which is not or to a lesser extent metabolised by CYP2D6 (not tramadol). In IMs with insufficient analgesia, a higher dose or alternative analgesic should be given. For tramadol, the recommendations for IMs and PMs are the same as the recommendation for codeine and IMs. UMs should receive an alternative drug not or to a lesser extent metabolised by CYP2D6 or the dose should be decreased to 40% of the commonly prescribed dose. Due to the absence of effect on clinical outcomes of oxycodone in PMs, IMs and UMs no action is required. DPWG classifies CYP2D6 genotyping for codeine "beneficial" and recommends testing prior to, or shortly after initiation of treatment in case of higher doses or additional risk factors. CYP2D6 genotyping is classified as "potentially beneficial" for tramadol and can be considered on an individual patient basis.