Fluoropy-*1/*1 Normal • Standard dose. CPIC rimidines *1/*2A, *1/*13, Reduced • Reduce initial dose 50% and titrate based *1/rs67376798A activity on toxicity or on pharmacokinetic test results (if available).
*2A/*2A, *2A/*13, Complete • Different non-fluoropyrimidine anticancer agent. *13/*13, rs67376798A/ deficiency rs67376798A
Irinotecan *1/*1, *1/*28 Normal • Standard starting dose.
*28/*28 Reduced • Reduce starting dose by at least one dose level. Or, Drug label • Dose > 250 mg/m2: Reduce starting dose 30% DPWG3 and increase in response to neutrophil count. Dose = 250 mg/m2: No dose adjustment.
Atazanavir *1/*1, *1/*36, Normal No reason to avoid prescribing atazanavir. Inform CPIC *36/*36, patient of risks. Based on this genotype, there is a rs887829 C/C less than 1 in 20 chance of stopping atazanavir for jaundice.
*1/*28, *1/*37, Intermediate No reason to avoid prescribing atazanavir. Inform *36/*28, *36/*37, patient of risks. Based on this genotype, there is a rs887829 C/T, *1/*6 less than 1 in 20 chance of stopping atazanavir for jaundice.
*28/*28, *28/*37, Reduced Consider alternative agent. Based on this *37/*37, rs887829 T/T genotype, there is a high (20–60%) likelihood of (*80/*80), *6/*6 developing jaundice that will result in discontinuation of atazanavir.
Thiopurines *1/*1 Normal, high • Standard starting dose. CPIC activity *1/*2, *1/*3A, Intermediate • Start at 30–70% of target dose and titrate *1/*3B, *1/*3C, activity every 2–4 weeks with close clinical monitoring of *1/*4 tolerability, eg, white blood cell counts and liver function tests.
TABLE 5–2 Gene-based dosing recommendations for selected drugs. (Continued) 1Diplotypes are shown as the two members of a chromosome pair, eg, *1/*1 indicates both chromosomes contain the *1 allele for that gene, whereas *1/*17 denotes a heterozygote with one *1 allele and one *17 allele. 2CPIC: Clinical Pharmacogenetics Implementation Consortium: Full drug-specific recommendations are available online at http://www.pharmgkb.org/page/cpic. 3DPWG: Dutch Pharmacogenetics Working Group: Full drug-specific recommendations are available online https://www.pharmgkb.org/page/dpwg. 4SVR: sustained viral response. 5IWPG: International Warfarin Pharmacogenetics Consortium.