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Informatics in Pharmacy

Common Pharmacogenomic SNPs and Interactions

December 5, 2021 By Dr. G, PharmD

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UM = ultrarapid metabolizer, EM = extensive metabolizer, IM = intermediate metabolizer, PM = poor metabolizer

Drug SNPTypesEffectRaceMisc 
IvacaftorCFTR     
amitriptylineCYP 2C19UM (R), EM, IM, PMPM = increased conc, side effects, UM = decreased concenPM =Common in Asians UM=Common in CaucasionsUM – Avoid or lower dose, IM/EM same, PM avoid or start at 50% dose.  Must calculate activity score 
citalopramCYP 2C19UM (R), EM, IM, PMPM = increased conc, side effects, UM = decreased concenPM =Common in Asians UM=Common in CaucasionsUM – Avoid or lower dose, IM/EM same, PM avoid or start at 50% dose.  Must calculate activity score 
escitalopramCYP 2C19UM (R), EM, IM, PMPM = increased conc, side effects, UM = decreased concenPM =Common in Asians UM=Common in CaucasionsUM – Avoid or lower dose, IM/EM same, PM avoid or start at 50% dose.  Must calculate activity score 
PlavixCYP2C19UM (R), EM, IM, PMProdrug – PM have decreased levels, UM have increased drug levelsPM =Common in Asians UM=Common in CaucasionsIM and PM should use alternative. Prasugrel is a prorug, but not CYP related.  Ticagrelor is not prodrug. 
SSRIsCYP2C19UM (R), EM, IM, PMPM = increased conc, side effects, UM = decreased concenPM =Common in Asians UM=Common in CaucasionsUM – Avoid or lower dose, IM/EM same, PM avoid or start at 50% dose.  Must calculate activity scoresee specific drugs
TricylicsCYP2C19UM (R), EM, IM, PMPM = increased conc, side effects, UM = decreased concenPM =Common in Asians UM=Common in CaucasionsUM – Avoid or lower dose, IM/EM same, PM avoid or start at 50% dose.  Must calculate activity scoresee specific drugs
PPICYP2C19UM (R), EM, IM, PM PM =Common in Asians UM=Common in Caucasions  
voriconazoleCYP2C19UM (R), EM, IM, PM New Terms: Plasma 3-4 times higher in PMS compared to Ems.  UM may have sub-thera levels (not as clear)PM =Common in Asians UM=Common in Caucasions2C19 polymorphism explains 50% of the variability. Adult specific and peditric specifif tables for this one.  NTI. Exposure can cause hepatotoxity, visual distburances, neurological side effects, etc.Also 2C9 and 3A4.  (Ultra rapid, Rapid (this has been split into two groups now, one is homozygous and one is not), Normal Metabolizer, Intermediate Metabolizer, Poor Metabolizer).  must still monitor drugs.
WarfarinCYP2C9EM, IM, PMIM and PM associated with lower dosesSome variants more common in AAdosage calculators available 
PhenytoinCYP2C9EM, IM, PMIM, decrease dose, PM decreased morePM= Mostly caucasiun Phenytoin needs 2 tests.  EM as usualy, IM decrease by 25%, PM decrease by 50%.   
PhenytoinCYP2C9EM, IM, PMEM as normal, IM = 25% of dose, PM 50% of dose Phenytoin needs 2 tests 
NSAIDsCYP2C9EM, IM, PM    
GlyburideCYP2C9EM, IM, PM    
SSRIsCYP2D6UM, EM, IM, PMUM =decreased concentrations, PM = increased concentrationsPM= Mostly caucasiun UM – Avoid or lower dose, IM/EM same, PM avoid or start at 50% dose.  Must calculate activity scorewatch for 2d6 inhibitors, see specific drugs
TricylicsCYP2D6UM, EM, IM, PMUM =decreased concentrations, PM = increased concentrationsPM= Mostly caucasiun UM – Avoid or lower dose, IM/EM same, PM avoid or start at 50% dose.  Must calculate activity scorewatch for 2d6 inhibitors, see specific drugs
nortriptylineCYP2D6UM, EM, IM, PMUM =decreased concentrations, PM = increased concentrationsPM= Mostly caucasiun UM – Avoid or lower dose, IM/EM same, PM avoid or start at 50% dose.  Must calculate activity scorewatch for 2d6 inhibitors
amitriptylineCYP2D6UM, EM, IM, PMUM =decreased concentrations, PM = increased concentrationsPM= Mostly caucasiun UM – Avoid or lower dose, IM/EM same, PM avoid or start at 50% dose.  Must calculate activity scorewatch for 2d6 inhibitors, also applies to imipramine and desipramine too
paroxetineCYP2D6UM, EM, IM, PMUM =decreased concentrations, PM = increased concentrationsPM= Mostly caucasiun UM – Avoid or lower dose, IM/EM same, PM avoid or start at 50% dose.  Must calculate activity scorewatch for 2d6 inhibitors
fluvoxamineCYP2D6UM, EM, IM, PMUM =decreased concentrations, PM = increased concentrationsPM= Mostly caucasiun UM – Avoid or lower dose, IM/EM same, PM avoid or start at 50% dose.  Must calculate activity scorewatch for 2d6 inhibitors
CodeineCYP2D6UM, EM, IM, PMProdrug, PM – lower concentration, UM = higherPM= Mostly caucasiun Beware of adding 2D6 inhibitors.Must calculate activity scoreDo not use in breastfeeding moms with known CYP2D6 UM.  Can harm baby.  Alternatives: morphine, non-opiod
tramadolCYP2D6UM, EM, IM, PMProdrug, PM = decresed response, UM = increased response and adverse effects.PM= Mostly caucasiun UM – Avoid, EM – As usual, IM – Consider alternative if it doesn’t work, PM avoid. Not as much evidenceDo not use in breastfeeding moms with known CYP2D6 UM.  Can harm baby.  Alternatives: morphine, non-opiod
hydrocodoneCYP2D6UM, EM, IM, PMProdrug, PM – lower concentration, UM = higherPM= Mostly caucasiun UM – Avoid, EM – As usual, IM – Consider alternative if it doesn’t work, PM avoidDo not use in breastfeeding moms with known CYP2D6 UM.  Can harm baby.  Alternatives: morphine, non-opiod
oxycodoneCYP2D6UM, EM, IM, PMProdrug, PM – lower concentration, UM = higherPM= Mostly caucasiun UM – Avoid, EM – As usual, IM – Consider alternative if it doesn’t work, PM avoidDo not use in breastfeeding moms with known CYP2D6 UM.  Can harm baby.  Alternatives: morphine, non-opiod
CodeineCYP3a4   not as much evidencealternatives: morphine, non-opiod
tegafurDPYDNormal, intermediate or low functionIM – increased conc, Low – much increased concen Normal – label recs, IM – decrase dose by 50%, titrate based on toxicity, low – DO NOT USEDPYD metabolizes to inactive form
5-FUDPYDNormal, intermediate or low functionIM – increased conc, Low – much increased concen Normal – label recs, IM – decrase dose by 50%, titrate based on toxicity, low – DO NOT USEDPYD metabolizes to inactive form
capecitabineDPYDNormal, intermediate or low functionIM – increased conc, Low – much increased concen Normal – label recs, IM – decrase dose by 50%, titrate based on toxicity, low – DO NOT USEDPYD metabolizes to inactive form
RasburicaseG6PD     
CarbamazepineHLA-B 15:02Not metabolism relatedPresence of 15:02=increased risk for TENS/SJS. Primarly in Asian or HAN Chinese, Vietnam, Cambodia, Runion Island, India, Hong KongDo not rechallenge. Do not initiate.  Should be pre-screened.  Also avoid phenytoin, fosphenytoin, oxcarbazepine, eslicarbazepine, lamotrigine 
PhenytoinHLA-B 15:02Not metabolism relatedPresence of 15:02=increased risk for TENS/SJS. Primarly in Asian or HAN Chinese, Vietnam, Cambodia, Runion Island, India, Hong KongDo not rechallenge. Do not initiate.  Should be pre-screened.  Also avoid phenytoin, fosphenytoin, oxcarbazepine, eslicarbazepine, lamotrigineAlso avoid phenytoin, fosphenytoin, oxcarbazepine, eslicarbazepine, lamotrigine
AbacavirHLA-B 57:01Not metabolism relatedPresence of 57:01=increased risk for TENS/SJS. Mostly in Southwest AsiansDo not rechallenge. Do not initiate.  Should be pre-screened.   
AllopurinolHLA-B 58:01Not metabolism relatedPresence of 58:01=increased risk for TENS/SJS.    
SimvastatinSLOCO1B1Normal, intermediate or low functionLF = decreased effect, increase side effects Not all statins are equally affected. OATP1b1 is affected. 
repaglinideSLOCO1B1Normal, intermediate or low functionLF = decreased effect, increase side effects Not all statins are equally affected. OATP1b1 is affected. 
ThiopurinesTPMTNormal, intermediate or low functionTPMT inactives drug Nm = normal dose, 2 week steady state, intermediate = 30-70% of dose, 2-4 weeks for SS, Low = 90% of dose, only three times a week, 4-6 weeks for steady state. Only use for low if malignency.inherited
AtazanavirUGT1A1     
WarfarinVKORC1decreaseddecreased mean less warfarin needed Vitamin K epoxide reductase 
       
Ondansetron CYP2D6UM, EM, IM, PMUM  decreased concentration UM should consider another choicegranisetron not metabolized by 2D6. Tripisetron is
TamoxifenCYP2D6UM, EM, IM, PMActive metabolite. PM have poorer drug response, less active metabolite.  Not as straight forward. No CPIC guideline. Don’t recommend testing as a tool.Dutch Working Group recomends in relapse. Level A on CPIC.  Most likely relevalent only postmenopausal women with ER-positive breast cancer deciding between aromatse inhib and tamoxifen.
ThiopurinesNUDT15Normal, intermediate or low function Asians and hispanics Low = 90% of dose 
IrinotecanUGT1A1UGT1AT*28decresed metabolism, increased accumulation and toxicity

Pro-drug, SN38 active metbolite inactivated and detoxified by a UDP-glucuronosyltransferase 
 No recs from CPIC.  May be pertinent to genotype in high dose (>240 mg/m2) situations. Watch neutrophil count7 TA repeats instead of 6 TA repeats. Homozygotes – Joubert’s syndrome

This chart was designed by Amanda Galiano, PharmD.
Sources: https://cpicpgx.org/ (CPIC Gudelines), https://www.pharmgkb.org/ (PharmGKB)

Filed Under: Explore, Guideline Materials and Tips, Pharmacogenomics

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