C. diff Risk


Oral Bioavailability


Approximate Cost


See drug monitoring information

PO: 400 mg PO q12h x 2 doses, then 200-300 mg PO q12h
May require dose adjustment if low body weight

IV: 6 mg/kg IV q12h x 2 doses, then 4 mg/kg IV q12h

Mild to moderate (Child-Pugh A/B) - Standard loading dose then reduce maintenance by 50%

Severe impairment (Child-Pugh C) - Should only be used if benefit outweighs risk

General Information

Common Usage

Infectious Diseases consultation recommended for use.

Drug Monitoring

Therapeutic drug monitoring may be helpful to ensure adequate concentrations and exclude toxicity.

QTc interval in patients at elevated risk

Monitor hepatic profile

Creatinine, electrolytes (K+, Mag+, Ca+)

Adverse Effects

  • QTc prolongation

  • Hepatic enzyme abnormalities

  • Rash - up to 20%

  • Visual disturbance

  • ¬†Fluorosis

  • GI upset

Major Interactions

CYP450 interactions ++

Other QTc prolonging agents

Voriconazole increases concentration of phenytoin. Phenytoin decreases concentration of voriconazole. Drug monitoring recommended.

Recommend review of patient medications due to high frequency of significant interactions.

Additional Information

Food may decrease oral absorption. Should be taken 1hr before or 1 hr after a meal.

Avoid/limit use of IV formulation in renal failure due to accumulation of vehicle (cyclodextrin).


Antimicrobial class: Triazole antifungal

Pregnancy category: D