Low
Excellent
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
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+)
QTc prolongation
Hepatic enzyme abnormalities
Rash - up to 20%
Visual disturbance
Fluorosis
GI upset
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.
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).
