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)
(CYP3A4 Inhibition)

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

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