Table 5. Effect of Voriconazole on Levels of Other Drugs
| Drug/Drug Class | Drug Level | Drug Dosage Adjustment |
|---|---|---|
| Sirolimus
(Rapamune®) (CYP3A4 Inhibition) |
Significantly increased | CONTRAINDICATED |
| Terfenadine,
astemizole, cisapride, pimozide, quinidine (CYP450 Inhibition) |
Drug levels likely increased | CONTRAINDICATED |
| Ergot
alkaloids (CYP450 Inhibition) |
Drug levels likely increased | CONTRAINDICATED |
| Cyclosporine (CYP3A4 Inhibition) |
AUC significantly increased | Decrease cyclosporine dose by one-half and follow levels |
| Tacrolimus
(Prograf®) (CYP3A4 Inhibition) |
Significantly increased | Decrease tacrolimus dose by one-third and follow levels |
| Phenytoin (Dilantin®) (CYP2C9 Inhibition) |
Significantly increased | Frequently monitor phenytoin levels and monitor for adverse effects |
| Warfarin
(Coumadin®) (CYP2C9 Inhibition) |
Increased INR/PT | Monitor INR/PT; may require dose adjustment of warfarin |
| Omeprazole
(Prilosec®) (CYP2C19/3A4 Inhibition) |
Significantly increased | If omeprazole dose > 40 mg/day decrease dose by one-half; other PPIs may require dose adjustment |
HIV Protease Inhibitors
(PIs) |
No
effects on indinavir; In-vitro studies show potential for interaction
|
Monitor for adverse effects and toxicity of PIs |
| Non-nucleoside reverse transcriptase inhibitors (NNRTIs) (CYP3A4 Inhibition) | Potential for increased levels | Monitor for adverse effects and toxicity of NNRTIs |
| HMG-CoA
Reductase Inhibitors (CYP3A4 Inhibition) |
Potential for increased levels | Monitor for adverse effects; may require dose adjustment of the HMG - CoA Reductase Inhibitor |
| Dihydropyridine
calcium channel blockers (CCBs) (CYP2C9 Inhibition) |
Potential for increased levels | Monitor for adverse effects; may require dose adjustment of CCB |
| Sulfonylurea (CYP2C9 Inhibition) |
Potential for increased levels | Monitor for hypoglycemia; may require dose adjustment |
| Vinka
alkaloids (CYP3A4 Inhibition) |
Potential for increased levels | Monitor for adverse events and neurotoxicity; may require dose adjustment of vinka alkaloids |
| Cyclophosphamide (CYP3A4 Inhibition) |
May prevent conversion to active metabolite | Unknown |
AUC = area-under-the-curve
INR = international normalized ratio
PT = prothrombin time
PPI = proton pump
inhibitor