Table 3. Examples of phenotype terms that trigger clinical decision support (CDS).

Gene	High Risk Phenotype	High Risk Drug	Example CDS provided in CPIC guideline	Reference
CYP2C19	CYP2C19 Ultrarapid Metabolizer	Citalopram	This patient is predicted to be a CYP2C19 ultrarapid metabolizer and may be at an increased risk of a poor response due to low plasma concentrations of citalopram. Consider selecting an alternative SSRI not extensively metabolized by CYP2C19.	Hicks, et al. (2015)17
CYP3A5	CYP3A5 Normal Metabolizer	Tacrolimus	Based on the genotype result, this patient is predicted to have lower tacrolimus serum drug levels if initiated on a standard tacrolimus starting dose. Consider increasing the starting dose to 1.5 times to 2 times the standard dose. Total starting dose should not exceed 0.3mg/kg/day. Further dose adjustments or selection of alternative therapy may be necessary due to other clinical factors (e.g., medication interactions, or hepatic function). Use therapeutic drug monitoring to guide dose adjustments.	Birdwell, et al. (2015)18
CYP2C9	CYP2C9 Intermediate Metabolizer	Phenytoin	Based on the genotype result, this patient is predicted to be a CYP2C9 Intermediate Metabolizer and is at increased risk for developing phenytoin-induced toxicities. Consider a 25% reduction of recommended starting maintenance dose. Subsequent maintenance doses should be adjusted according to therapeutic drug monitoring and response.	Caudle, et al. (2014)40
HLA-B*57:01	HLA-B*57:01 positive	Abacavir	The HLA-B*57:01 allele has been detected in this patient. This allele is associated with high risk of severe hypersensitivity to abacavir. DO NOT prescribe abacavir per the FDA’s black box warning. Please choose an alternate antiretroviral.	Martin, et al. (2014)19