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
Fosphenytoin
Cerebyx
Use with caution
Your body clears this drug more slowly, so it can build up and cause nervous system side effects. A lower starting dose and blood level checks are suggested.
The genes behind this label
The guidelines read one gene for fosphenytoin. 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 fosphenytoin 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 clears this drug more slowly, so it can build up and cause nervous system side effects. A lower starting dose and blood level checks are suggested.
- What it means
- May result in higher systemic concentrations and higher adverse reaction risk (central nervous system toxicity). Consider starting at the lower end of the dosage range and monitor serum concentrations. 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 fosphenytoin 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
- Consider starting at the lower end of the dosage range and monitor serum concentrations. CYP2C9*3 carriers may be at higher risk of severe skin reactions; consider avoiding fosphenytoin as an alternative to carbamazepine in them.
About fosphenytoin
Fosphenytoin (Cerebyx) is an injectable prodrug of phenytoin: the body converts it to phenytoin within minutes, and all of its antiseizure effect comes from that phenytoin.
- Used for
- Generalized tonic-clonic status epilepticus; preventing and treating seizures during neurosurgery; short-term replacement for oral phenytoin when it cannot be taken by mouth
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.