Extended-Spectrum Triazole — Aspergillus / Mucor / Prophylaxis in Immunocompromised Pregnancy: eMC §4.6: there is insufficient information on the use of posaconazole in pregnant women and animal studies have shown reproductive toxicity; the potential risk for humans is unknown. Women of childbearing potential must use effective contraception during treatment. Posaconazole must NOT be used during pregnancy unless the benefit to the mother clearly outweighs the potential risk to the foetus. Breast-feeding must be stopped on initiation of treatment.

Posaconazole

Brand names: Noxafil

Posaconazole is a broad-spectrum triazole antifungal used for the treatment and prophylaxis of invasive fungal infections, including aspergillosis and infections caused by some moulds such as mucormycosis, particularly in immunocompromised patients.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Loading dose 300 mg twice a day on the first day, then 300 mg once a day thereafter

Route: Oral - three 100 mg gastro-resistant tablets per dose, swallowed whole with water, with or without food; do not crush, chew or break. For invasive aspergillosis the SPC states the 300 mg dose may alternatively be given as the 300 mg concentrate for solution for infusion, and switching between intravenous and oral administration is appropriate when clinically indicated

Frequency: Twice daily on day 1 (loading), then once daily

eMC §4.2 (Posaconazole 100 mg gastro-resistant tablets). Treatment should be initiated by a physician experienced in the management of fungal infections or in the supportive care of high-risk patients. NON-INTERCHANGEABILITY: the tablets must NOT be used interchangeably with posaconazole oral suspension - the two formulations differ in dosing frequency, administration with food and plasma concentrations achieved; follow the specific dose recommendations for each formulation. Tablets generally give higher plasma exposures than the oral suspension under both fed and fasted conditions and are the preferred formulation to optimise plasma concentrations. INDICATIONS AND DURATION - Treatment of invasive aspergillosis (ADULTS ONLY): 300 mg twice daily on day 1, then 300 mg once daily; recommended total duration 6-12 weeks. Refractory invasive fungal infection, or intolerance to first-line therapy: same loading and maintenance dose; duration based on severity of the underlying disease, recovery from immunosuppression and clinical response. Prophylaxis of invasive fungal infections: same loading and maintenance dose; duration based on recovery from neutropenia or immunosuppression - in acute myelogenous leukaemia or myelodysplastic syndromes, start several days before the anticipated onset of neutropenia and continue for 7 days after the neutrophil count rises above 500 cells per mm3. HEPATIC IMPAIRMENT: limited data (including Child-Pugh C) show increased plasma exposure but do not suggest that dose adjustment is necessary; exercise caution because of the potential for higher plasma exposure. PAEDIATRIC: the dose in Table 1 (300 mg twice daily day 1, then 300 mg once daily) applies to patients from 2 years of age weighing MORE than 40 kg, i.e. the same as adults. Patients 2 years and older weighing 40 kg or less should receive the gastro-resistant powder and solvent for oral suspension - refer to that formulation's SmPC for dosing (no per-kg dose is given in this SPC). Safety and efficacy in children below 2 years of age have not been established and no clinical data are available. Verify any under-18 use against a children's formulary.

Dose adjustments

Renal

eMC §4.2: an effect of renal impairment on the pharmacokinetics of posaconazole is not expected and no dose adjustment is recommended. The US labelling agrees that no adjustment is necessary for oral dosing in mild to severe renal impairment.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients (eMC §4.3); the US labelling extends this to known hypersensitivity to other azole antifungal agents
Co-administration with ergot alkaloids (eMC §4.3)
Co-administration with the CYP3A4 substrates terfenadine, astemizole, cisapride, pimozide, halofantrine or quinidine - increased plasma concentrations may lead to QTc prolongation and rare torsades de pointes (eMC §4.3)
Co-administration with the HMG-CoA reductase inhibitors simvastatin, lovastatin and atorvastatin (eMC §4.3)
Co-administration during the initiation and dose-titration (ramp-up) phase of venetoclax in chronic lymphocytic leukaemia (eMC §4.3)
US labelling additionally contraindicates co-administration with sirolimus (posaconazole increases sirolimus blood concentrations approximately 9-fold)

Side effects

Nausea, vomiting and diarrhoea - among the most frequently reported serious related adverse reactions (eMC §4.8)
Pyrexia and increased bilirubin (eMC §4.8); hepatic reactions including mild to moderate elevations in ALT, AST, alkaline phosphatase, total bilirubin and/or clinical hepatitis, rarely severe with fatal outcome (eMC §4.4)
Neutropenia (common); thrombocytopenia, leukopenia, anaemia, eosinophilia, lymphadenopathy and splenic infarction (uncommon); haemolytic uraemic syndrome, thrombotic thrombocytopenic purpura, pancytopenia, coagulopathy and haemorrhage (rare)
QTc prolongation and torsades de pointes (eMC §4.4, US §5.2)
Headache, cough and hypokalaemia are listed among the common adverse reactions in the US labelling; the US labelling also lists pseudoaldosteronism (new or worsening hypertension with abnormal laboratory findings)

Interactions

Posaconazole is a CYP3A4 inhibitor (a strong inhibitor per the US labelling) - plasma concentrations of drugs predominantly metabolised by CYP3A4 may be increased; use only under specific circumstances and consider dosage adjustment with monitoring (eMC §4.4, US §7)
Ergot alkaloids, terfenadine, astemizole, cisapride, pimozide, halofantrine, quinidine, simvastatin, lovastatin, atorvastatin and venetoclax during initiation/ramp-up in CLL - co-administration is contraindicated (eMC §4.3)
Benzodiazepines metabolised by CYP3A4 (midazolam, triazolam, alprazolam) - risk of prolonged sedation and possible respiratory depression; co-administer only if clearly necessary and consider dose adjustment of the benzodiazepine (eMC §4.4)
Vincristine - concomitant azole antifungals including posaconazole have been associated with neurotoxicity (eMC §4.4)
Other QTc-prolonging medicinal products - posaconazole must not be given with CYP3A4 substrates known to prolong the QTc interval, and should be used with caution with other QTc-prolonging drugs; correct potassium, magnesium and calcium disturbances before and during therapy (eMC §4.4)
Rifabutin, phenytoin, efavirenz, cimetidine and esomeprazole (US labelling §7) - avoid co-administration unless the benefit outweighs the risks; these can decrease posaconazole plasma concentrations. Posaconazole is metabolised via UDP-glucuronosyltransferase and is a P-glycoprotein substrate
Ciclosporin and tacrolimus (US labelling §5.1) - posaconazole increases their concentrations; reduce the dose and monitor concentrations frequently
The eMC §4.5 interaction section was not captured in this bundle - clinician to review it in the full SPC

Clinical monograph

How it works

It inhibits fungal cytochrome P450-dependent lanosterol 14-alpha-demethylase, blocking ergosterol synthesis and disrupting the integrity of the fungal cell membrane.

Prescribing in practice

It is a potent CYP3A4 inhibitor and is contraindicated with several drugs (including certain statins, ergot alkaloids and some agents that prolong the QT interval), so a thorough interaction check is essential before prescribing.
Absorption differs between formulations: the older oral suspension depends heavily on food and gastric acidity, whereas the gastro-resistant tablet and intravenous forms give more reliable exposure.
It can prolong the QT interval and cause hepatotoxicity, so caution is needed in patients with relevant risk factors.

Monitoring

Monitor liver function and electrolytes, and use therapeutic drug monitoring of plasma concentrations to confirm adequate exposure where indicated.

Counselling the patient

If you are taking the oral suspension, take it with food or a nutritional supplement to help absorption.
Tell the team about all your other medicines, as posaconazole interacts with many drugs.
Report yellowing of the skin or eyes, dark urine or palpitations.

Evidence & guidelines

Posaconazole prophylaxis reduced invasive fungal infections in high-risk neutropenic and graft-versus-host disease patients in pivotal randomised trials.

Reference: ESCMID/ECMM Aspergillosis Guidelines; ECMM/ISHAM Mucormycosis Guidelines; EORTC MSG Posaconazole Prophylaxis Trial; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways