TABLE 2.

DOSING RECOMMENDATIONS FOR ONDANSETRON AND TROPISETRON BASED ON CYP2D6 GENOTYPE

Phenotype	Implication	Therapeutic Recommendation	Classification of Recommendationa	Consideration for alternative 5- HT3 receptor antagonists antiemeticsb
CYP2D6 ultrarapid metabolizer	Increased metabolism to less active compounds when compared to normal metabolizers and is associated with decreased response to ondansetron and tropisetron (i.e. vomiting).	Select alternative drug not predominantly metabolized by CYP2D6 (i.e. granisetron).c	Moderate	Dolasetron, palonosetron, and ramosetron are also metabolized by CYP2D6. Limited evidence is available regarding the utilization of CYP2D6 genetic variation to guide use of these drugs.
CYP2D6 normal metabolizer	Normal metabolism	Initiate therapy with recommended starting dose.c	Strong
CYP2D6 intermediate metabolizer	Very limited data available for CYP2D6 intermediate metabolizers.	Insufficient evidence demonstrating clinical impact based on CYP2D6 genotype. Initiate therapy with recommended starting dose.c	No recommendation
CYP2D6 poor metabolizer	Very limited data available for CYP2D6 poor metabolizers.	Insufficient evidence demonstrating clinical impact based on CYP2D6 genotype. Initiate therapy with recommended starting dose.c	No recommendation

^aRating scheme described in the Supplement.

^bCPIC strength of recommendation: No Recommendation. See rating scheme described in the Supplement.

^cDrug-drug interactions and other patient characteristics (e.g., age, renal function, and liver function) should be considered when selecting alternative therapy.