fidaxomicin
Macrocyclic antibiotic· Brands: Dificid, DificlirPO
Mechanism of action
Fidaxomicin is a macrocyclic antibiotic that inhibits bacterial RNA polymerase, leading to inhibition of protein synthesis. It is bactericidal against Clostridioides difficile.
Pharmacokinetics
Fidaxomicin is minimally absorbed from the gastrointestinal tract, remaining in the gut where it acts locally. It is metabolised in the gut to its active metabolite, OP-1118. Both the parent drug and metabolite are excreted primarily in faeces.
Indications & dosing
Treatment of Clostridioides difficile infection (CDI) in adults
Standard duration is 10 days.
- adult · PO: 200 mg twice daily · Standard duration is 10 days.
Treatment of Clostridioides difficile infection (CDI) in pediatric patients (6 months to 17 years)
Same dose as adults; duration 10 days.
- pediatric · PO: 200 mg twice daily · Weight-based dose, not the same as adults: 200 mg twice daily only for children of 35 kg and above (80 mg twice daily for 12.5-17.5 kg; 120 mg twice daily for 17.5-35 kg); duration 10 days.
Contraindications & precautions
- Hypersensitivity to fidaxomicin or any excipient · Known or suspected allergy to the drug or its components.
- Systemic infections (extra-intestinal) · Fidaxomicin is not absorbed systemically and is only effective intraluminally; not indicated for systemic infections.
- Use only for Clostridioides difficile infection; not effective for systemic infections.
- Caution in pregnancy and breastfeeding as limited data; use only when clearly necessary.
- Caution when coadministered with P-glycoprotein inhibitors (e.g., cyclosporine) or substrates (e.g., digoxin), as fidaxomicin is a substrate and inhibitor of P-gp.
- Monitor for signs of allergic reaction, including anaphylaxis; discontinue treatment if severe hypersensitivity occurs.
- Consider the risk of C. difficile recurrence in patients with prior episodes or fulminant colitis.
Adverse effects
- Nausea
- Vomiting
- Abdominal pain
- Diarrhoea
- Flatulence
- Constipation
- Anaphylaxis and angioedemaserious
- Rash
Monitoring, pregnancy & toxicity
- Clinical response (resolution of diarrhoea) · Throughout treatment and after completion
- Adverse effects (nausea, vomiting, abdominal pain) · During treatment
- Recurrence of Clostridioides difficile infection · After treatment
- Pregnancy: There are limited data on fidaxomicin use in pregnancy. It is not recommended unless the potential benefit outweighs the risk. Systemic absorption is minimal, but caution is advised.
- Toxicity: Gastrointestinal disturbances (nausea, vomiting, abdominal pain) · Manage symptomatically; no specific antidote.
- Toxicity: Hypersensitivity reactions (rash, pruritus) · Discontinue if severe; treat symptomatically.
- Toxicity: Overdose (unlikely due to minimal systemic absorption) · Supportive care; not dialysable.
Clinical notes
Fidaxomicin is used to treat Clostridioides difficile infection, particularly for recurrent episodes. It has a narrower spectrum than vancomycin, which helps preserve the normal gut microbiome. The standard course in adults is 200 mg orally twice daily for 10 days.
Log in to read the full fidaxomicin monograph
A free account unlocks the complete drug reference, the interaction checker, prescription practice and every other learning tool.
BNF; local formulary