Adults

Vaginal candidiasis: 200 mg twice daily for 1 day or 200 mg once daily for 3 days. Onychomycosis: Pulse therapy (200 mg twice daily for 1 week, followed by 3 weeks off, repeated for 2-3 cycles) or continuous therapy (200 mg once daily for 3 months). Systemic fungal infections: 100-400 mg daily, depending on the infection type and severity, often for prolonged periods.

Elderly

Use with caution due to potential decreased hepatic or renal function and concurrent diseases/medications. Dose adjustment may be necessary.

Renal_impairment

Use with caution. Dosage adjustment may be required, particularly for severe impairment. Consider monitoring plasma concentrations.

Onset

Clinical improvement usually observed within days to weeks, depending on the infection type.

Excretion

Approximately 35% of a dose is excreted in urine (mainly as inactive metabolites) and 3-18% in feces (as unchanged drug and metabolites).

Half life

Plasma elimination half-life is approximately 15-42 hours, with steady-state concentrations achieved within 1-2 weeks of daily dosing.

Absorption

Oral absorption is variable and increases when taken with a full meal. Bioavailability is approximately 55%. Peak plasma concentrations are reached within 2-5 hours.

Metabolism

Extensively metabolized in the liver by the cytochrome P450 3A4 (CYP3A4) isoenzyme into several metabolites, including the active metabolite hydroxyitraconazole.

Statins

Increased risk of myopathy/rhabdomyolysis with HMG-CoA reductase inhibitors (e.g., simvastatin, lovastatin) due to inhibited metabolism by itraconazole.

QT-prolonging drugs

Itraconazole can inhibit the metabolism of certain drugs that prolong the QT interval (e.g., quinidine, dofetilide), leading to increased risk of ventricular arrhythmias.

Calcium channel blockers

Itraconazole can inhibit the metabolism of dihydropyridine calcium channel blockers (e.g., felodipine, verapamil), increasing their plasma concentrations and potentially adverse effects.

CYP3A4 inhibitors/inducers

Itraconazole is metabolized by CYP3A4. Strong inhibitors (e.g., ritonavir, indinavir, clarithromycin, erythromycin) can increase itraconazole levels. Strong inducers (e.g., rifampicin, phenytoin, carbamazepine, phenobarbital) can decrease itraconazole levels, reducing efficacy.