CPIC® Guideline for Thiopurines and TPMT and NUDT15

Most recent guideline publication:

Clinical Pharmacogenetics Implementation Consortium Guidelines for thiopurine dosing based on TPMT and NUDT15 genotypes: 2018 Update (November 2018)

Updates since publication:

February 2019: Based on a recent publication confirming NUDT15*9 function and association with toxicity to thiopurines, NUDT15*9 function has been changed from “uncertain function” to “no function” (PMID: 30728528). The NUDT15 allele definition table, NUDT15 allele functionality table, NUDT15 diplotype-phenotype table and NUDT15 frequency table have been updated accordingly.

Tables and figures provided in the main manuscript of the guideline:

Figure 1. Metabolism of azathioprine, thioguanine, and mercaptopurine
Table 1. Assignment of likely TPMT and NUDT15 phenotypes based on genotypes
Table 2. Recommended Dosing of Thiopurines by TPMT phenotype
Table 3. Recommended Dosing of Thiopurines by NUDT15 phenotype
Figure 2. Recommended Starting Doses of Thiopurines by TPMT and NUDT15 phenotype

Supplement to: Clinical Pharmacogenetics Implementation Consortium Guidelines for thiopurine dosing based on TPMT and NUDT15 genotpes: 2018 Update (November 2018)

Tables and figure included in the supplement or referenced in the guidelinea:

Figure S1. Idealized depictions of TPMT activity in erythrocytes from a normal, healthy, non-transfused population
Supplemental Table S1. Evidence linking TPMT genotype with Thiopurine phenotype
Supplemental Table S2. Evidence linking NUDT15 genotype with Thiopurine phenotype
TPMT allele definition table 
TPMT allele functionality table 
TPMT frequency table 
TPMT diplotype-phenotype table 
NUDT15 allele definition table 
NUDT15 allele functionality table 
NUDT15 frequency table 
NUDT15 diplotype-phenotype table 

Gene resource mapping

TPMT gene resource mappings 

NUDT15 gene resource mappings 

Drug resource mapping




Clinical decision support:b

Thiopurines pre- and post-test alerts and flow chart 

aSome of the tables included in the guideline may have been updated online, particularly to reflect newly described or newly characterized alleles. These include the gene-specific information tables ( that support CPIC guidelines by providing information regarding star (*) allele definitions, allele function, allele frequency by major ethnic groups, translations of diplotype to phenotype, and gene resource mappings.

bThese resources support the adoption of CPIC guidelines into the electronic health record with clinical decision support and provide information that clinical implementers find helpful.

Older versions of this guideline:

Update (April 2013):

Original publication (March 2011):

This guideline has been endorsed by the American Society of Health-System Pharmacists (ASHP).