Review medication list and hepatic status before starting fluconazole.
Absolute: hypersensitivity to azoles. Relative: QT prolongation risk, hepatic disease, renal impairment, and pregnancy when alternatives available.
Hypersensitivity to fluconazole or other azole antifungals — prior anaphylaxis, serious cutaneous reactions, or hepatic injury attributed to an azole precludes re-exposure.
Coadministration with CYP3A4-dependent agents that markedly prolong the QT interval (for example, cisapride) because torsades de pointes and sudden death have been reported.
Baseline QT prolongation, structural heart disease, or electrolyte disturbances; obtain ECG and correct potassium or magnesium before initiation.
Chronic hepatic impairment; although rare, fluconazole can cause severe hepatotoxicity, so monitor transaminases and discontinue if signs of liver injury develop.
Renal impairment with creatinine clearance below 50 mL/min; reduce the maintenance dose in proportion to renal function to prevent accumulation.
Pregnancy, especially during the first trimester; high-dose or prolonged courses have been associated with congenital anomalies, so reserve for severe systemic mycoses when benefits outweigh risks.