No CYP2C19 enzyme activity. Greatly reduced conversion to secondary amines, which may affect response or adverse effects (e.g., anticholinergic, CNS, and cardiac) based on CYP2C19 alone.
Important Instructions: Please use CYP2D6 Activity Score to select the appropriate recommendation below.
CYP2D6 Ultrarapid Metabolizer (Activity score >2.25)
Increased CYP2D6 enzyme activity. Increased risk of treatment failure based on CYP2D6 alone.
Therapeutic Recommendation
- Avoid use of tertiary amines or if warranted, utilize therapeutic drug monitoring to guide dose adjustments.
CYP2D6 Normal – Ultrarapid Metabolizer (Activity Score >1.5+ or 2+)*
Normal to increased CYP2D6 enzyme activity. Possible increased risk of treatment failure based on CYP2D6 alone.
Therapeutic Recommendation
- Avoid use of tertiary amines or if warranted, utilize therapeutic drug monitoring to guide dose adjustments.
CYP2D6 Normal Metabolizer (Activity Score of 1.25-2.25)*
Normal CYP2D6 enzyme activity. Normal response expected based on CYP2D6 alone.
Therapeutic Recommendation
- Avoid use of tertiary amines or if warranted, decrease dose by 50%.
CYP2D6 Intermediate – Ultrarapid Metabolizer (Activity Score 0.25+. 0.5+, 0.75+ or 1+)*
Possible increases, normal, or decreased CYP2D6 enzyme activity. Exact activity cannot be determine because of gene duplication and assay limitations. Possible increase risk of treatment failure OR increase rise of adverse effects (e.g., anticholinergic, CNS, and cardiac) based on CYP2D6 alone.
Therapeutic Recommendation
- Avoid use of tertiary amines or if warranted, utilize therapeutic drug monitoring to guide dose adjustments.
CYP2D6 Intermediate Metabolizer (Activity Score 0.25-1)*
Decreased CYP2D6 enzyme activity. Increased risk of adverse effects (e.g., anticholinergic, CNS, and cardiac) based on CYP2D6 alone.
Therapeutic Recommendation
- Avoid use of tertiary amines or if warranted, utilize therapeutic drug monitoring to guide dose adjustments.
CYP2D6 Poor Metabolizer (Activity Score 0)
No CYP2D6 enzyme activity. Increased risk of adverse effects (e.g., anticholinergic, CNS, and cardiac) based on CYP2D6 alone.
Therapeutic Recommendation
- Avoid use of tertiary amines or if warranted, utilize therapeutic drug monitoring to guide dose adjustments.
*Previously some labs have designated an Activity Score of 1 as Normal Metabolizers.