Antimicrobials · Echinocandins
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Micafungin acts by inhibiting the synthesis of 1,3-beta-D-glucan, a critical component of the fungal cell wall.
Echinocandins are the first-line therapy for candidemia and invasive Candida infections in most patients.
Micafungin is administered exclusively via the intravenous route due to poor oral bioavailability.
Micafungin exhibits fungicidal activity against Candida species but is only fungistatic against Aspergillus species.
Echinocandins are preferred over fluconazole in patients who are hemodynamically unstable or have recent azole exposure.
Micafungin has a favorable safety profile with minimal cytochrome P450 drug-drug interactions compared to azoles.
Common adverse effects of micafungin include histamine-mediated infusion reactions, elevated liver enzymes, and phlebitis.
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A 62-year-old male in the ICU for post-operative complications following a bowel resection develops a persistent fever despite broad-spectrum antibacterial coverage. Blood cultures return positive for Candida glabrata. The patient is currently on cyclosporine for a prior renal transplant and has a history of elevated liver function tests. He is currently hemodynamically unstable requiring vasopressor support.
Which of the following is the most appropriate antifungal agent to initiate?
Micafungin
Micafungin is the preferred treatment for hemodynamically unstable patients with candidemia and is safer than azoles in patients with potential drug-drug interactions or hepatic concerns.
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Classification
Echinocandin antifungal; non-competitive 1,3-beta-D-glucan synthase inhibitor.
Indications
Candidemia, invasive candidiasis, and esophageal candidiasis.
Mechanism of Action
Inhibits 1,3-beta-D-glucan synthase, disrupting the fungal cell wall integrity.
Side Effects
Phlebitis, headache, histamine-mediated infusion reactions.
Contraindications / Monitoring
Hypersensitivity; monitor LFTs and CBC.
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Mechanism of Action
Micafungin inhibits the synthesis of 1,3-beta-D-glucan, an essential component of the fungal cell wall. By targeting this enzyme, it causes osmotic instability and fungal cell death. It is considered fungicidal against most *Candida* species.
Unique Properties
Unlike azoles, echinocandins have minimal CYP450 interactions, making them safer in patients on complex drug regimens. They are the gold standard for hemodynamically unstable patients with suspected fungal sepsis.
Indications
Indicated for candidemia and invasive candidiasis in both adult and pediatric patients. It is also used for esophageal candidiasis and as prophylaxis in patients undergoing hematopoietic stem cell transplantation.
Pharmacokinetics
Micafungin is administered via IV infusion only. It undergoes extensive hepatic metabolism and is not significantly cleared by the kidneys, requiring no dose adjustment in renal failure.
Side Effects & Adverse Events
Common effects include nausea, vomiting, and phlebitis at the injection site. Histamine-mediated infusion reactions including rash and pruritus can occur. Rare but serious hepatotoxicity requires monitoring of liver enzymes.
Contraindications
Hypersensitivity to micafungin or other echinocandins is an absolute contraindication. Use with caution in patients with pre-existing severe hepatic impairment.
Monitoring
Monitor LFTs (ALT/AST/Bilirubin) periodically for signs of drug-induced injury. Perform baseline and periodic CBC to monitor for potential leukopenia or anemia.
Clinical Pearls
Think of micafungin as the first-line choice for candidemia in the ICU. It is ineffective against *Cryptococcus* and *Aspergillus* (only fungistatic against the latter), so do not use for primary treatment of those infections.