CYP2C9Your two copies: *1/*2
Intermediate metabolizer
One copy works and one works less well.
1.5 activity scoreTypical: 2Clears warfarin, phenytoin, celecoxib and some other pain relievers.
This result changes the label.
Example report. Made from Leslie Knope's DNA data so you can see what yours will look like. Get your own report
AnticonvulsantsExample report
Phenytoin
Dilantin
Use with caution
Your body breaks down this drug more slowly, so it can build up. That raises the risk of side effects on the brain and nerves.
The genes behind this label
The guidelines read one gene for phenytoin. Each card shows the two copies this person inherited and what they mean.
What the guidelines say
What each guideline says about your result.
CYP2C9Intermediate metabolizer (activity score 1.5)
CPIC guideline
Use as directed Evidence: moderateRead the guideline (Clinical Pharmacogenetics Implementation Consortium, opens in a new tab)
- In plain words
- Your body slows the drug slightly, but no dose changes are usually needed.
- What it means
- Slightly reduced phenytoin metabolism; however, this does not appear to translate into increased side effects.
- What the guideline suggests
- No adjustments needed from typical dosing strategies. Subsequent doses should be adjusted according to therapeutic drug monitoring, response, and side effects. An HLA-B*15:02 negative test does not eliminate the risk of phenytoin-induced SJS/TEN, and patients should be carefully monitored according to standard practice.
FDA drug label
Use with caution See the FDA table (U.S. Food and Drug Administration, opens in a new tab)
- In plain words
- Your body breaks down this drug more slowly, so it can build up. That raises the risk of side effects on the brain and nerves.
- What it means
- May result in higher systemic concentrations and higher adverse reaction risk (central nervous system toxicity). Refer to FDA labeling for specific dosing recommendations. Carriers of CYP2C9*3 alleles may be at increased risk of severe cutaneous adverse reactions. Consider avoiding phenytoin as an alternative to carbamazepine in patients who are CYP2C9*3 carriers. Genotyping is not a substitute for clinical vigilance and patient management.
- What the label suggests
- Refer to FDA labeling for dosing. CYP2C9*3 carriers may be at higher risk of severe skin reactions; consider avoiding phenytoin as an alternative to carbamazepine in them.
About phenytoin
Phenytoin (Dilantin) is an older antiseizure medicine with a narrow gap between an effective and a toxic blood level.
- Used for
- Tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures; preventing and treating seizures during or after neurosurgery
Others in anticonvulsants
Compare all 4 anticonvulsantsDon't change a dose on your own. Bring this report to your prescriber or pharmacist. They can weigh it with everything else they know about you.