Micafungin

Micafungin is an intravenous echinocandin used for candidaemia, invasive candidiasis, oesophageal candidiasis and antifungal prophylaxis in stem cell transplantation. It needs no loading dose, has few interactions and no dose adjustment for kidney or mild to moderate liver impairment.

Class. Echinocandin antifungal.

Mechanism. Inhibits 1,3-beta-D-glucan synthase and fungal cell wall synthesis; FKS mutations cause resistance.

Pharmacokinetics. Intravenous only, highly protein bound, half life 11 to 17 hours, metabolised by catechol-O-methyltransferase, excreted mainly in faeces. Low urine and cerebrospinal fluid penetration.

Candidaemia and invasive candidiasis (adults). - 100 mg intravenously once daily; no loading dose. - Duration: 14 days after the first negative blood culture and resolution of symptoms.

Oesophageal candidiasis. 150 mg once daily for 14 to 21 days.

Prophylaxis in stem cell transplantation or neutropenia. 50 mg once daily until neutrophil recovery.

Salvage invasive aspergillosis (unlicensed). 100 to 150 mg once daily.

Children. 2 mg/kg once daily (maximum 100 mg); over 40 kg, adult doses; neonates 10 mg/kg for meningoencephalitis in specialist care.

Maximum: 150 mg daily in adults. Loading dose: none. Titration: none.

Contraindications. Hypersensitivity to echinocandins.

Serious adverse effects. Hepatotoxicity, anaphylaxis, haemolytic anaemia, severe skin reactions.

Common adverse effects. Phlebitis, nausea, diarrhoea, raised liver enzymes, hypokalaemia and rash.

Interactions. Raises sirolimus and nifedipine exposure; monitor. Few others.

Common prescribing errors. Using it for cryptococcal or central nervous system infection in adults, wrong infusion duration, and ignoring liver tests.

Special groups. - Pregnancy: avoid unless essential. - Breastfeeding: limited data. - Children: weight-based; neonates higher doses. - Older adults: no adjustment. - Kidney impairment: no adjustment. - Liver impairment: mild to moderate: no adjustment; severe: use with caution and liver tests.

Formulations. Powder for infusion 50 mg and 100 mg vials.

Administration. Reconstitute with 0.9% sodium chloride or 5% glucose; infuse over 1 hour.

Baseline. Liver tests, creatinine, potassium.

Monitoring. Liver tests twice weekly in the first week, then weekly; blood cultures until clear.

Stopping thresholds. Stop for anaphylaxis, haemolysis, severe skin reaction or marked hepatotoxicity.

Referral and escalation. Specialist review for candidaemia, ophthalmology review, and treatment failure.