Fidaxomicin: uses, dosing, side effects & brands
Fidaxomicin is a macrolide antibacterial sold in the U.S. under one brand, for pseudomembranous enterocolitis. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
Key facts
- Drug class
- Macrolide Antibacterial
- Treats
- Pseudomembranous Enterocolitis
- Available as
- Powder
- Sold as
- Dificid
- Prescription?
- Prescription only
- Generic available?
- Not in our catalog
- What the pharmacy pays
- about $4760 for a 30-count supply — not your price
How fidaxomicin is dosed
From the FDA label for Dificid (application NDA201699). Other fidaxomicin products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
DIFICID is administered orally with or without food. ( 2.1 ) Adults One 200 mg tablet orally twice daily for 10 days. ( 2.2 ) Pediatrics (6 Months to Less than 18 Years of Age) Tablets Pediatric patients weighing at least 12.5 kg and able to swallow tablets: One 200 mg tablet orally twice daily for 10 days. ( 2.3 ) Oral Suspension Pediatric patients weighing at least 4 kg: Weight-based dosing of the oral suspension twice daily for 10 days using an oral dosing syringe, as specified in Table 1 in the full prescribing information. ( 2.3 ) For instructions on preparation and administration of DIFICID oral suspension, see full prescribing information. ( 2.4 ) 2.1 Important Administration Instructions DIFICID is available for oral administration as 200 mg tablets and as granules for oral suspension (40 mg/mL (200 mg/5 mL) when reconstituted). DIFICID is administered orally with or without food. 2.2 Adult Patients The recommended dosage for adults is one 200 mg DIFICID tablet orally twice daily for 10 days. 2.3 Pediatric Patients (6 Months to Less than 18 Years of Age) Tablets The recommended dosage for pediatric patients weighing at least 12.5 kg and able to swallow tablets is one 200 mg DIFICID tablet administered orally twice daily for 10 days. If unable to swallow tablets, pediatric patients may be dosed with DIFICID oral suspension as recommended in Table 1 below. Oral…
Fidaxomicin side effects
The most common adverse reactions in adults (incidence ≥2%) are nausea, vomiting, abdominal pain, gastrointestinal hemorrhage, anemia, and neutropenia. ( 6 ) The most common adverse reactions in pediatric patients (incidence ≥5%) treated with DIFICID are pyrexia, abdominal pain, vomiting, diarrhea, constipation, increased aminotransferases, and rash. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Merck Sharp & Dohme LLC at 1-877-888-4231 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Adults The safety of DIFICID 200 mg tablets taken twice a day for 10 days was evaluated in 564 adult patients with CDAD in two active-controlled trials with 86.7% of patients receiving a full course of treatment. Thirty-three adult patients receiving DIFICID (5.9%) withdrew from trials as a result of adverse reactions (AR). The types of AR resulting in withdrawal from the study varied considerably. Vomiting was the primary adverse reaction leading to discontinuation of dosing; this occurred at an incidence of 0.5% in both the DIFICID and vancomycin patients in Phase 3 trials. The most common…
Who shouldn’t take fidaxomicin
DIFICID is contraindicated in patients who have known hypersensitivity to fidaxomicin or any other ingredient in DIFICID [see Warnings and Precautions (5.1) ] . DIFICID is contraindicated in patients who have known hypersensitivity to fidaxomicin or any other ingredient in DIFICID. ( 4 )
Fidaxomicin drug interactions
Fidaxomicin and its main metabolite, OP-1118, are substrates of the efflux transporter, P-glycoprotein (P-gp), which is expressed in the gastrointestinal tract. 7.1 Cyclosporine Cyclosporine is an inhibitor of multiple transporters, including P-gp. When cyclosporine was co-administered with DIFICID, plasma concentrations of fidaxomicin and OP-1118 were significantly increased but remained in the ng/mL range [see Clinical Pharmacology (12.3) ] . Concentrations of fidaxomicin and OP-1118 may also be decreased at the site of action (i.e., gastrointestinal tract) via P-gp inhibition; however, concomitant P-gp inhibitor use had no attributable effect on safety or treatment outcome of fidaxomicin-treated adult patients in controlled clinical trials. Based on these results, fidaxomicin may be co-administered with P-gp inhibitors and no dose adjustment is recommended.
Every fidaxomicin product we track (1)
Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.
Only one: Dificid.
What fidaxomicin pills look like
Imprint codes, colour and shape from the FDA’s labelling data. Match the imprint on your pill — or search any imprint.
How long fidaxomicin keeps
The date on a sealed pack is not the only one: some fidaxomicin labels start a second clock once the product is opened or mixed, as short as 12 days.
Does fidaxomicin expire? The in-use limits and storage rules from its labelsFidaxomicin and breastfeeding
From LactMed, the US National Library of Medicine’s Drugs and Lactation Database — quoted, not rewritten.
Full LactMed record for fidaxomicin: levels in milk, effects in breastfed infants, and the drugs it would consider insteadNo information is available on the use of fidaxomicin during breastfeeding. Because it is poorly absorbed orally, it is not likely to reach the bloodstream of the infant or cause any adverse effects in breastfed infants.
National Institute of Child Health and Human Development, record revised December 15, 2024. LactMed states its information is not a substitute for professional judgement.
What people report to the FDA about fidaxomicin
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 969 reports naming fidaxomicin, and the FDA flagged 90% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:
- clostridium difficile infection209 reports
- diarrhoea94 reports
- clostridium difficile colitis60 reports
- pyrexia50 reports
- acute kidney injury44 reports
- nausea43 reports
- septic shock42 reports
- treatment failure42 reports
Read these as a signal, not a rate. A report does not mean fidaxomicin caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.
Source: openFDA drug/event (FAERS), retrieved July 25, 2026.
Related calculators
Frequently asked questions
What is fidaxomicin?
DIFICID (fidaxomicin) is a macrolide antibacterial drug for oral administration.
What kind of drug is fidaxomicin?
The FDA classifies fidaxomicin as a macrolide antibacterial. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.
Can you take fidaxomicin with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run fidaxomicin against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
What forms does fidaxomicin come in?
Across the brands we track, fidaxomicin is currently marketed as powder, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic fidaxomicin?
We do not currently list a generic-labelled fidaxomicin product. That does not always mean none exists — it means none appears under a generic name in the FDA data we track. Ask your pharmacist.
Cite this page
- APA
- pharmaranks. (2026, July 24). Fidaxomicin: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/fidaxomicin
- MLA
- “Fidaxomicin: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/fidaxomicin.
We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Read the full FDA label for fidaxomicin on DailyMed (NIH) ↗.