Pharmacogenomics
Tramadol Therapy and <em>CYP2D6</em> Genotype
2015 Sep 10 [updated 2024 Aug 21]. In: Pratt VM, Scott SA, Pirmohamed M, Esquivel B, Kattman BL, Malheiro AJ, editors. Medical Genetics Summaries [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2012–.
ABSTRACT
Tramadol (brand names ConZip, Ultram, UltramER, Odolo) is an analgesic used to treat moderate to severe pain. It is used for a variety of pain conditions, including post-operative pain, cancer pain, and musculoskeletal pain. Tramadol is a centrally acting opioid analgesic with mu-opioid binding activity as well as weak inhibition of reuptake of norepinephrine and serotonin.
The CYP2D6 enzyme converts tramadol to the active metabolite, O-desmethyltramadol (M1), which has a significantly higher affinity for the mu-opioid receptor than tramadol. The M1 metabolite is up to 6 times more potent than tramadol in producing analgesia.
Individuals who have reduced CYP2D6 activity are known as “intermediate metabolizers” and those with absent CYP2D6 activity are known as “poor metabolizers.” The standard recommended doses of tramadol may not provide adequate pain relief in these individuals because of reduced levels of M1. Whereas in individuals who have increased CYP2D6 activity (“ultrarapid metabolizers”), standard doses of tramadol may result in a higher risk of adverse events because of increased exposure to M1.
The 2021 FDA-approved drug label warns that individuals who are ultrarapid metabolizers (UMs) should not use tramadol because of the risk of life-threatening respiratory depression and signs of opiate overdose (for example, extreme sleepiness, confusion, or shallow breathing) (Table 1) (1).
The prevalence of CYP2D6 UM varies but is thought to be present in approximately 1–10% of Caucasians (European, North American), 3–4% of Blacks (African Americans), and 1–2% of East Asians (Chinese, Japanese, Korean). The frequency of UM phenotype has been reported to be even higher in some groups, including Ashkenazi Jews and regional populations in the Middle East.
Furthermore, tramadol is not recommended in nursing mothers due to the potential exposure to high levels of M1 causing life-threatening respiratory depression, if the mother is a UM. At least one death was reported in a nursing infant who was exposed to high levels of morphine in breast milk because the mother was an UM of codeine, which—similar to tramadol—is activated by CYP2D6 metabolism.
Tramadol is contraindicated for all children younger than age 12 and for all individuals under the age of 18 when being used for post-operative analgesia following tonsillectomy or adenoidectomy, or both. The label warns that life-threatening respiratory depression and death have occurred in children who received tramadol, and in at least one case, the child was an UM of tramadol.
The Clinical Pharmacogenetics Implementation Consortium (CPIC) recommends that for an individual identified as a CYP2D6 UM, a different non-CYP2D6 dependent analgesic should be used to avoid the risk of severe toxicity with standard dosing of tramadol. The CPIC also recommends avoiding tramadol in individuals identified as CYP2D6 poor metabolizers (PMs) due to the possibility of lack of effect (Table 2) (2).
The Dutch Pharmacogenetics Working Group (DPWG) of the Royal Dutch Association for the Advancement of Pharmacy (KNMP) provides dosing recommendations for tramadol based on CYP2D6 genotype (Table 3). The DPWG states it is not possible to calculate a dose adjustment for tramadol, because when the ratio of tramadol and M1 is altered, the nature and total analgesic effect of tramadol also changes. For CYP2D6 UM, DPWG recommends selecting an alternative drug to tramadol - but not codeine, which is also metabolized by CYP2D6. Alternative drugs include morphine (not metabolized by CYP2D6) and oxycodone (which is metabolized by CYP2D6 to a limited extent, but this does not result in differences in side effects in clinical practice). For CYP2D6 poor (PM) and intermediate metabolizers (IM), DPWG recommends increasing the dose of tramadol, and if this does not have the desired effect, selecting an alternative drug (not codeine) (Table 3) (3).
Lecanemab Therapy and <em>APOE</em> Genotype
2024 Aug 12. In: Pratt VM, Scott SA, Pirmohamed M, Esquivel B, Kattman BL, Malheiro AJ, editors. Medical Genetics Summaries [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2012–.
ABSTRACT
Lecanemab, brand name Leqembi, is a monoclonal antibody that targets amyloid beta (Aβ) aggregates for the treatment of Alzheimer disease (AD) (1). It is approved by the US Food and Drug Administration (FDA) for individuals with mild cognitive impairment (MCI) or mild dementia stage AD with confirmed amyloid pathology (1). Tests to confirm Aβ pathology in the clinical trials included positron emission tomography (PET) or cerebrospinal fluid (CSF) measurement of the Aβ42/Total Tau ratio (2). This disease-modifying medication is based on the amyloid cascade hypothesis, which suggests Aβ aggregates are a key driver in AD pathogenesis and that the removal of Aβ aggregates should slow cognitive decline.
Lecanemab is associated with amyloid-related imaging abnormalities (ARIA) due to edema (ARIA-E) or hemorrhage (ARIA-H) from blood vessels in the brain (3, 4). Individuals who have one or 2 copies of the AD risk-associated apolipoprotein E (APOE) ε4 (NM_000041.4:c.388T>C) allele have an increased risk of ARIA-E or -H (1) (Table 1). These individuals require additional monitoring during the first year of treatment (5). The FDA-approved label reports that concomitant antithrombotic medication (aspirin, antiplatelet, or anticoagulant) with lecanemab therapy resulted in intracerebral hemorrhage in 2.5% of individuals during clinical trials (1).
The appropriate use recommendations from the Alzheimer’s Disease and Related Disorders Therapeutics Work Group state that individuals requiring anticoagulants should not be treated with lecanemab until additional data regarding this interaction are available (5). Both the FDA-approved label and Alzheimer’s Disease and Related Disorders Therapeutics Work group encourage clinicians to consider participation in a registry for AD treatment to gather additional real-world data on lecanemab therapy (1, 5).
Introduction
2016 Sep 15 [updated 2024 Jun 28]. In: Pratt VM, Scott SA, Pirmohamed M, Esquivel B, Kattman BL, Malheiro AJ, editors. Medical Genetics Summaries [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2012–.
NO ABSTRACT
Dabrafenib Therapy and <em>BRAF</em> Genotype
2017 Aug 15 [updated 2023 Dec 4]. In: Pratt VM, Scott SA, Pirmohamed M, Esquivel B, Kattman BL, Malheiro AJ, editors. Medical Genetics Summaries [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2012–.
ABSTRACT
Dabrafenib (brand name Tafinlar) is a kinase inhibitor used in the treatment of individuals with unresectable or metastatic melanoma, metastatic non-small cell lung cancer (NSCLC), locally advanced or metastatic anaplastic thyroid cancer (ATC), pediatric low-grade glioma (LGG), and other unresectable or metastatic solid tumors with specific BRAF variants. Dabrafenib can be used as a single agent to treat melanoma with the BRAF valine 600 to glutamic acid (V600E) variant or in combination with the MEK inhibitor trametinib to treat multiple tumor types with BRAF V600E or V600K variants. (1)
The BRAF protein is an intracellular kinase in the mitogen-activated protein kinases (MAPK) pathway. Functionally, BRAF regulates essential cell processes such as cell growth, division, differentiation, and apoptosis. The gene BRAF is also a proto-oncogene—when mutated, it transforms normal cells into cancerous cells.
Variation in the kinase domain of BRAF is associated with various cancers. The most common BRAF variant, V600E, constitutively activates the kinase and causes cell proliferation in the absence of growth factors that would usually be needed. The V600E variant is detected in approximately 50% of melanomas, 25% of ATC, 2% of NSCLC, and 20% of pediatric LGGs (2, 3, 4, 5, 6, 7, 8).
The FDA-approved label for dabrafenib states that the presence of BRAF mutation in tumor specimens (V600E for dabrafenib monotherapy; V600E or V600K for dabrafenib plus trametinib) should be confirmed using an FDA-approved test before starting treatment with dabrafenib. Dabrafenib is not indicated for the treatment of individuals with wild-type BRAF tumors, or the treatment of colorectal cancer due to intrinsic resistance to BRAF inhibitor monotherapy. (1)
The label also states that individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency should be monitored for signs of hemolytic anemia while taking dabrafenib (1). However, it is important to note that an independent literature review by the Clinical Pharmacogenetics Implementation Consortium found no publications to support or refute this risk and thus issued no guidance for G6PD deficiency and dabrafenib therapy (9).
Atazanavir Therapy and <em>UGT1A1</em> Genotype
2023 Oct 17. In: Pratt VM, Scott SA, Pirmohamed M, Esquivel B, Kattman BL, Malheiro AJ, editors. Medical Genetics Summaries [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2012–.
ABSTRACT
Atazanavir is indicated for managing human immunodeficiency virus (HIV) infection as part of a multi-drug regimen (1). While it was once widely recommended as a first-line therapy, it is now primarily suggested as a second-line therapeutic option due to potential adverse effects leading to discontinuation of therapy (2, 3). Atazanavir can cause hyperbilirubinemia (not associated with liver injury) leading to jaundice, which is a common cause of drug discontinuation. Individuals with 2 decreased-function alleles for UGT1A1 are most likely to experience jaundice leading to atazanavir discontinuation, although this can occur despite the individual having a reference UGT1A1 genotype (4). The Clinical Pharmacogenetics Implementation Consortium (CPIC) recommends that when an individual is a known UGT1A1 poor metabolizer, an alternative therapy should be considered particularly when jaundice is of concern to the individual (Table 1) (4). The US Food and Drug Administration (FDA) approved drug label states that certain comedications that depend upon UGT1A1 or the cytochrome P450 family member CYP3A are contraindications for atazanavir therapy due to the potential for elevated plasma concentrations of these comedications (1).
Siponimod Therapy and <em>CYP2C9</em> Genotype
2023 Aug 9. In: Pratt VM, Scott SA, Pirmohamed M, Esquivel B, Kattman BL, Malheiro AJ, editors. Medical Genetics Summaries [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2012–.
ABSTRACT
Siponimod (brand name Mayzent) is a sphingosine-1-phosphate (S1P) receptor modulator used in the treatment and management of relapsing forms of multiple sclerosis (MS) in adults. It works by targeting lymphocytes to decrease the number of circulating cells that are associated with MS symptomatic attacks and disease progression and may also have a direct neuroprotective impact. Siponimod strongly binds to the S1P type 1 and type 5 receptors that are abundantly expressed on lymphocytes and multiple other cell types in the central nervous system (CNS). Off-target interactions and effects on cardiac cells may occur, also. The use of a dose titration schedule is recommended to decrease the risk of bradycardia (see Table 1, Table 2) (1, 2). This medication is approved for multiple forms of relapsing MS (RMS) in the United States (1) and for active, secondary progressive disease in Europe and Canada (2, 3).
Siponimod is metabolized by members of the cytochrome P450 family, specifically CYP2C9 and, to a lesser extent CYP3A4. The CYP2C9 gene is polymorphic and activity scores are used to categorize diplotype into phenotype. Decreased CYP2C9 metabolic activity is associated with increased exposure to siponimod and increased risk of adverse effects. Therefore, individuals with the CYP2C9*3/*3 diplotype (activity score = 0) are contraindicated from taking siponimod (1, 2). Individuals with one copy of the no-function *3 allele (diplotype with activity scores of 0.5 or 1.0) are advised to take half the standard maintenance dose (1, 2). Consideration of genotype and activity score is essential for CYP2C9-based siponimod dosing because labeled dose recommendations are not categorized by phenotype. In the US, there is a modified titration schedule for individuals with a CYP2C9*3 allele (Table 1)(1); however, the European prescribing guidelines do not modify the titration schedule for individuals with a single copy of the CYP2C9*3 allele (heterozygous for CYP2C9*3) (Table 2) (2). The Dutch Pharmacogenetics Working Group (DPWG) of the Royal Dutch Association for the Advancement of Pharmacy similarly recommends a 50% reduced maintenance dosage for intermediate metabolizers (IM) (Table 3) (4). It should be noted that dose recommendations in the Siponimod package label are limited to diplotypes consisting of only CYP2C9 *1,*2, and *3 alleles due to lack of clinical data on the impact of other decreased or no-function alleles(1), while other medication and testing guidelines also consider*5, *6, *8, and *11 (5, 6).
Belinostat Therapy and <em>UGT1A1</em> Genotype
2023 Jul 20. In: Pratt VM, Scott SA, Pirmohamed M, Esquivel B, Kattman BL, Malheiro AJ, editors. Medical Genetics Summaries [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2012–.
ABSTRACT
Belinostat (brand name Beleodaq) is a histone deacetylase (HDAC) inhibitor, approved for the treatment of relapsed or refractory peripheral T-cell lymphomas (PTCLs) (1). Belinostat targets 3 classes of HDACs (I, II and IV), resulting in higher levels of acetylation of both histone and non-histone proteins, thus reversing the changes in protein acetylation that are frequently disrupted during oncogenesis. Belinostat is administered as an infusion at a rate of 1000 mg/m2 for 30 minutes on days 1–5 of a 21-day cycle (1).
Belinostat has a relatively short half-life and is primarily metabolized by uridine diphosphate (UDP)-glucuronosyltransferase 1A1 (UGT1A1)-mediated glucuronidation, with minor contributions from other UGT and cytochrome P450 (CYP) enzymes (1, 2). Genetic variation at the UGT1A1 locus can result in decreased enzyme activity and thus increased exposure to belinostat. The US Food and Drug Administration (FDA)-approved drug label recommends a 25% decrease in dose for individuals who are known to be homozygous for the UGT1A1*28 reduced function allele (Table 1) (1). Additional indications for dose reduction include grade 3 or 4 adverse reactions or significant decrease in neutrophil or platelet counts following belinostat administration (1). Some studies have suggested that other variant alleles may also lead to increased belinostat exposure, such as UGT1A1*60; however, no specific recommendations for dose reduction have been made for these alleles by either the FDA or other professional pharmacogenetic consortia. Belinostat should not be administered with other medications that can inhibit UGT1A1 function (1), such as nilotinib, ketoconazole, or ripretinib.
Primaquine Therapy and <em>G6PD</em> and <em>CYP2D6</em> Genotype
2023 Jul 6. In: Pratt VM, Scott SA, Pirmohamed M, Esquivel B, Kattman BL, Malheiro AJ, editors. Medical Genetics Summaries [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2012–.
ABSTRACT
Primaquine is a potent antimalarial medication indicated for the radical cure of malaria caused by Plasmodium vivax (P. vivax) and Plasmodium ovale (P. ovale) species (1, 2). Malaria is a blood borne infection caused by infection of Plasmodium parasites that is spread by mosquitos. The P. vivax and P. ovale species present a particular challenge to treat because the parasitic life cycle includes a dormant, liver-specific stage that is not susceptible to other antimalarial medications. Thus, primaquine is often used with other therapies such as chloroquine or artemisinin-based medicines that target the reproductive, active forms of the parasite. Primaquine is also used to prevent transmission of malaria caused by Plasmodium falciparum (P. falciparum) species. A single, low dose (SLD) of primaquine has gametocidal activity, which does not cure the individual but does provide malaria transmission control.
Primaquine is a pro-drug that must be activated by the cytochrome P450 (CYP) enzyme system. Metabolism by the cytochrome P450 member 2D6 (CYP2D6) and cytochrome P450 nicotinamide adenine dinucleotide phosphate (NADPH):oxidoreductase (CPR) generates 2 hydroxylated active metabolites that generate hydrogen peroxide (H2O2). This causes significant oxidative stress to the malarial parasite and the host human cells. Individuals who are glucose-6-phosphate dehydrogenase (G6PD) deficient are particularly susceptible to oxidative stress and may experience acute hemolytic anemia (AHA). Before starting a course of primaquine, individuals should be tested for G6PD deficiency to ensure safe administration (1, 2). According to the FDA-approved drug label, individuals with severe G6PD deficiency should not take primaquine (Table 1) (1).
The World Health Organization (WHO) recommends that individuals with G6PD deficiency should be treated with a modified course of primaquine therapy. The recommended course for individuals with G6PD deficiency is a single dose once per week for 8 weeks, while the standard course is daily administration for 14 days (Table 2) (2). The Clinical Pharmacogenetics Implementation Consortium (CPIC) reports that the risk of adverse effects of primaquine therapy for G6PD-deficient individuals is dose-dependent, with the SLD regimen presenting the least risk (Table 3) (3).
Primaquine is contraindicated during pregnancy and is not recommended for breastfeeding individuals when the G6PD status of the baby is unknown (1, 2). Primaquine is not approved for individuals under 6 months of age. Individuals with acute illness that are prone to granulocytopenia or individuals taking another hemolytic medication are also contraindicated from taking primaquine. (1)
Chloroquine Therapy and <em>G6PD</em> Genotype
2023 May 16. In: Pratt VM, Scott SA, Pirmohamed M, Esquivel B, Kattman BL, Malheiro AJ, editors. Medical Genetics Summaries [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2012–.
ABSTRACT
Chloroquine is used for the treatment of uncomplicated malaria and extra-intestinal amebiasis. Malaria is caused by infection of Plasmodium parasites. Chloroquine is active against the erythrocytic forms of susceptible strains of Plasmodium falciparum (P. falciparum), Plasmodium malariae (P. malariae), Plasmodium ovale (P. ovale), and Plasmodium Vivax (P. vivax). Chloroquine is not active against the gametocytes and the exoerythrocytic forms including the hypnozoite stage (P. vivax and P. ovale) of the Plasmodium parasites. Additionally, resistance to chloroquine and hydroxychloroquine has been reported in Plasmodium species, thus chloroquine therapy is not indicated if the infection arose in a region with known resistance. Chloroquine is used in first-line treatment of P. vivax malaria with primaquine. Studies have indicated chloroquine is effective against the trophozoites of Entamoeba histolytica (E. histolytica), which causes amebic dysentery, or amebiasis. (1) Chloroquine also has off-label uses for treatment of rheumatic diseases and has been investigated as a potential antiviral therapy as well as an adjuvant chemotherapy for several types of cancer. (2, 3, 4, 5)
Chloroquine accumulates in cellular acidic compartments such as the parasitic food vacuole and mammalian lysosomes, leading to alkalinization of these structures. This change in pH can impair the action of enzymes responsible for the formation of hemozoin by the parasite from ingestion of the host’s hemoglobin; this reaction occurs in the parasitic vacuole (6). Thus, chloroquine targets the blood-stage of the malaria parasites but cannot eliminate dormant hypnozoites and must be administered with a drug that targets the dormant parasitic form (1). Chloroquine, developed in the 1940s, has been superseded as the first-line recommended antimalarial therapy by both the US Centers for Disease Control (CDC) and World Health Organization (WHO), with the exceptions of during the first trimester of pregnancy or for malarial prophylaxis of a pregnant individual who is also deficient for glucose-6-phosphate dehydrogenase (G6PD) (7, 8). Among antimalarial medications, chloroquine is less likely than other medicines to cause hemolysis in G6PD-deficient individuals; however, the FDA-approved drug label states there is still a risk of hemolysis (Table 1) (1). In contrast, the Clinical Pharmacogenetics Implementation Consortium (CPIC) performed a systematic review of the available clinical literature and found low-to-no risk of acute hemolytic anemia for individuals with G6PD deficiency who take hydroxychloroquine or chloroquine (9) (Table 2). It should be noted that G6PD deficiency has a range of severity; CPIC advises caution for all medications when used by an individual with a severe G6PD deficiency with chronic non-spherocytic hemolytic anemia (CNSHA).
Clopidogrel Therapy and <em>CYP2C19</em> Genotype
2012 Mar 8 [updated 2022 Dec 1]. In: Pratt VM, Scott SA, Pirmohamed M, Esquivel B, Kattman BL, Malheiro AJ, editors. Medical Genetics Summaries [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2012–.
ABSTRACT
Clopidogrel (brand name Plavix) is an antiplatelet medicine that reduces the risk of myocardial infarction (MI) and stroke in individuals with acute coronary syndrome (ACS), and in individuals with atherosclerotic vascular disease (indicated by a recent MI or stroke, or established peripheral arterial disease) (1). Clopidogrel is also indicated in combination with aspirin for individuals undergoing percutaneous coronary interventions (PCI), including stent placement.
The effectiveness of clopidogrel depends on its conversion to an active metabolite, which is accomplished by the cytochrome P450 2C19 (CYP2C19) enzyme. Individuals who have 2 loss-of-function copies of the CYP2C19 gene are classified as CYP2C19 poor metabolizers (PM). Individuals with a CYP2C19 PM phenotype have significantly reduced enzyme activity and cannot activate clopidogrel via CYP2C19, which means the drug will have a reduced antiplatelet effect. Approximately 2% of Caucasians, 4% of African Americans, 14% of Chinese, and 57% of Oceanians are CYP2C19 PMs (2). The effectiveness of clopidogrel is also reduced in individuals who are CYP2C19 intermediate metabolizers (IM). These individuals have one loss-of-function copy of CYP2C19, with either one normal function copy or one increased function copy. The frequency of the IM phenotype is more than 45% in individuals of East Asian descent, more than 40% in individuals of Central or South Asian descent, 36% in the Oceanian population, approximately 30% in individuals of African descent, 20–26% in individuals of American, European, or Near Eastern descent, and just under 20% in individuals of Latino descent (2).
The 2022 FDA-approved drug label for clopidogrel includes a boxed warning on the diminished antiplatelet effect of clopidogrel in CYP2C19 PMs (Table 1). The warning states that tests are available to identify individuals who are CYP2C19 PMs, and to consider the use of another platelet P2Y12 (purinergic receptor P2Y, G-protein coupled 12) inhibitor in individuals identified as CYP2C19 PMs.
The 2022 Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline for clopidogrel recommends that for individuals with ACS or non-ACS indications who are undergoing PCI, being treated for peripheral arterial disease (PAD), or stable coronary artery disease following MI, an alternative antiplatelet therapy (for example, prasugrel or ticagrelor) should be considered for CYP2C19 PMs if there is no contraindication (Table 2) (3). Similarly, CPIC strongly recommends that CYP2C19 IMs should avoid clopidogrel for ACS or PCI but makes no recommendations for other cardiovascular indications (Table 2). For neurovascular indications, CPIC recommends avoidance of clopidogrel for CYP2C19 PMs and consideration of alternative medications for both IMs and PMs if not contraindicated (Table 3) (3).
The Dutch Pharmacogenetics Working Group (DPWG) of the Royal Dutch Association for the Advancement of Pharmacy (KNMP) have also made antiplatelet therapy recommendations based on CYP2C19 genotype. For individuals with ACS who undergo PCI, they recommend an alternative antiplatelet agent in PMs, and for IMs they recommend choosing an alternative antiplatelet agent or doubling the dose of clopidogrel to 150 mg daily dose, 600 mg loading dose (Table 4) (4).
Oxycodone Therapy and <em>CYP2D6</em> Genotype
2022 Oct 4. In: Pratt VM, Scott SA, Pirmohamed M, Esquivel B, Kane MS, Kattman BL, Malheiro AJ, editors. Medical Genetics Summaries [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2012–.
ABSTRACT
Oxycodone (brand names OxyContin, Roxicodone, Xtampza ER, and Oxaydo), is an opioid analgesic used for moderate to severe pain caused by various conditions for which alternative analgesic treatments are inadequate.(1) Oxycodone exerts its analgesic affects by binding to the mu-opioid receptors (MOR) in the central and peripheral nervous system. While it is an effective pain reliever, this agent also has a high potential for addiction, abuse, and misuse.
Oxycodone is metabolized by members of the cytochrome P450 (CYP) enzyme superfamily. The CYP3A4, CYP3A5, and CYP2D6 enzymes convert oxycodone to either less-active (CYP3A4 and CYP3A5) or more-active (CYP2D6) metabolites. Most of the analgesic effect is mediated by oxycodone itself, rather than its metabolites. Variation at the CYP3A4 and CYP3A5 loci leading to altered enzyme activity is rare. A handful of altered-function alleles are known, but there is no documented evidence to support altered oxycodone response in the presence of these variant alleles. The FDA approved drug label for oxycodone cautions that co-medication with CYP3A inhibitors or inducers may lead to altered pharmacokinetics and analgesia, but does not discuss genotype-based recommendations for prescribing (1).
Genetic variation at the CYP2D6 locus has conflicting evidence regarding altered response of individuals to oxycodone therapy. Thus, the Clinical Pharmacogenetics Implementation Consortium (CPIC) has determined that there is insufficient evidence to recommend alterations to standard clinical use based on CYP2D6 genotype (2). Similarly, the Dutch Pharmacogenetics Working Group (DPWG) of the Royal Dutch Association for the Advancement of Pharmacy (KNMP) recognizes the drug-gene interaction between CYP2D6 and oxycodone but states that the interaction does not affect analgesia achieved by the medication (3, 4). The PharmGKB online resource reports that drug labels in Switzerland (regulated by Swissmedic) state that CYP2D6 variation can alter oxycodone response (5, 6).
Interactions among drugs from polypharmacy may be further enhanced by genetic variation, but there are no professional recommendations to alter prescribing based on drug-drug-gene interactions. Regardless of genotype, oxycodone is contraindicated in individuals with significant respiratory depression, acute or severe bronchial asthma, known or suspect gastrointestinal obstruction, or known hypersensitivity to the medication (1).
Codeine
2021 Aug 16. Drugs and Lactation Database (LactMed) [Internet]. Bethesda (MD): National Library of Medicine (US); 2006–.
ABSTRACT
Maternal use of codeine during breastfeeding can cause infant drowsiness, central nervous system depression and possibly even death, with pharmacogenetics possibly playing a role.[1,2] Newborn infants seem to be particularly sensitive to the effects of even small dosages of narcotic analgesics. Once the mother's milk comes in, it is best to provide pain control with a nonnarcotic analgesic and limit maternal intake of oral codeine to 2 to 4 days at a low dosage with close infant monitoring, especially in the outpatient setting.[2-4] If the baby shows signs of increased sleepiness (more than usual), difficulty breastfeeding, breathing difficulties, or limpness, a physician should be contacted immediately.[5] Excessive sedation in the mother often correlates with excess sedation in the breastfed infant. Following these precautions can lower the risk of neonatal sedation.[6] Numerous professional organizations and regulatory agencies recommend that other agents are preferred over codeine or to avoid codeine completely during breastfeeding;[7-11] however, other opioid alternatives have been studied less and may not be safer.[12,13]
Dihydrocodeine
2021 Jun 21. Drugs and Lactation Database (LactMed) [Internet]. Bethesda (MD): National Library of Medicine (US); 2006–.
ABSTRACT
Maternal use of oral narcotics during breastfeeding can cause infant drowsiness, central nervous system (CNS) depression and even death. Like codeine, pharmacogenetics probably plays a role in the extent of CNS depression. Newborn infants seem to be particularly sensitive to the effects of even small dosages of narcotic analgesics. Dihydrocodeine possibly caused severe respiratory depression in one newborn infant whose mother was taking the drug for cough. Once the mother's milk comes in, it is best to provide pain control with a nonnarcotic analgesic and limit maternal intake of hydromorphone to a few days at a low dosage with close infant monitoring. If the baby shows signs of increased sleepiness (more than usual), difficulty breastfeeding, breathing difficulties, or limpness, a physician should be contacted immediately. Because there is little published experience with dihydrocodeine during breastfeeding, an alternate drug may be preferred, especially while nursing a newborn or preterm infant.