Micafungin

Micafungin is a semisynthetic derivative of a Coleophoma empetri fermentation product. Mechanistically it is identical to caspofungin — inhibition of the FKS-encoded 1,3-beta-D-glucan synthase complex, producing fungicidal activity against Candida and hyphal-tip damage in Aspergillus. What separates it clinically is pharmacology rather than mechanism: it is metabolised by arylsulfatase and catechol-O-methyltransferase rather than significantly by CYP3A4, so it has minimal interactions with calcineurin inhibitors and requires no loading dose and no renal or mild hepatic adjustment. That combination makes it the default echinocandin in transplant and ICU patients on complicated drug regimens. Like the rest of the class it does not cover Cryptococcus or Mucorales, and it penetrates the CNS, eye and urine poorly.

Targets: Beta-1,3-D-glucan synthase (FKS1), Fungal cell wall

• · 100 mg daily with no loading dose. Continue for at least 14 days after the first negative blood culture. Some centres use 150 mg daily in critically ill or high-weight patients, which is off-label but well tolerated.
• · 150 mg daily, typically for 14-21 days and at least 14 days beyond symptom resolution.
• · 50 mg daily, continued until neutrophil recovery — typically around 18 days in the pivotal trial.

Work out your exact syringe units →

• commonNausea and vomiting
• commonTransaminase elevation— Usually mild and reversible.
• commonHeadache
• commonHypokalaemia and hypomagnesaemia
• uncommonInfusion reactions— Rash, pruritus, flushing and rarely hypotension, mostly with rapid infusion.
• rareHaemolysis and haemolytic anaemia— Rare but labelled; monitor haemoglobin if it appears.

• Known hypersensitivity to micafungin or other echinocandins.
• Not effective against Cryptococcus, Mucorales or Fusarium.
• Not appropriate for fungal meningitis, endophthalmitis or urinary tract candidiasis given poor penetration into those sites.

• cautionsirolimus — Micafungin raises sirolimus AUC by roughly 20%; sirolimus levels need monitoring and possible dose reduction.
• cautionnifedipine — Modest increase in nifedipine exposure.
• cautionitraconazole — Small increase in itraconazole AUC.
• redundantcaspofungin — Same class, same target; use one or the other.
• synergytacrolimus — Notably, unlike caspofungin, micafungin has no clinically significant effect on tacrolimus or cyclosporine levels — which is exactly why transplant units favour it.

• · Liver function tests at baseline and periodically during therapy.
• · CBC, given the rare haemolysis signal.
• · Serum potassium and magnesium.
• · Follow-up blood cultures until clearance in candidaemia, plus a dilated eye examination.

Prescription-only injectable, approved in the US, EU, Japan and most markets; generics available.

• Kuse et al. 2007, micafungin versus liposomal amphotericin B for candidaemia and invasive candidiasis (trial)
• van Burik et al. 2004, micafungin versus fluconazole for prophylaxis in stem-cell transplantation (trial)
• Mycamine (micafungin sodium) US prescribing information (label)

Echinocandin inhibition of beta-1,3-glucan synthase, as with caspofungin, but with a simpler clinical profile: no loading dose, no hepatic dose adjustment, and minimal cytochrome-mediated interaction. It is the echinocandin of choice where drug interactions matter, particularly in transplant recipients on calcineurin inhibitors.

Same class limitations as caspofungin - no Cryptococcus cover and poor penetration into urine, CSF and eye. The mistake specific to micafungin is assuming it needs a loading dose because caspofungin does; it does not, and giving one achieves nothing.

• Beta-1,3-glucan synthase — Non-competitive

  Fungal cell wall synthesis failure

Steady state within a few days without loading.

• ?A historical rodent hepatic tumour signal appears in the European label and has never been shown to translate to humans; its clinical relevance remains unresolved.