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Generic name: fidaxomicin systemic

Brand names: Dificid

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Tablet, Oral:

Dificid: 200 mg [contains soybean lecithin]


Mechanism of Action

Inhibits RNA polymerase sigma subunit resulting in inhibition of protein synthesis and cell death in susceptible organisms including C. difficile; bactericidal



Oral: Minimal systemic absorption


Largely confined to the gastrointestinal tract; in single- and multiple-dose studies, fecal concentrations of fidaxomicin and its active metabolite (OP-1118) are very high while serum concentrations are minimally detectable to undetectable


Intestinal hydrolysis to less active metabolite (OP-1118)


Feces (>92% as unchanged drug and metabolites); urine (<1% as metabolite)

Use in Specific Populations

Special Populations: Elderly

Plasma concentrations were approximately 2- to 4-fold higher in elderly patients versus nonelderly patients.

Use: Labeled Indications

Treatment of Clostridioides (formerly Clostridium) difficile infection (CDI) in adults

Note: The 2017 Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA) guidelines for Clostridioides (formerly Clostridium) difficile Infection in adults and children recommend fidaxomicin as a treatment option for the initial episode of CDI (non-severe and severe), first recurrence (if vancomycin given for the initial episode), and second or subsequent recurrence (IDSA/SHEA [McDonald 2018]).


Hypersensitivity to fidaxomicin or any component of the formulation

Dosage and Administration

Dosing: Adult

Clostridioides (formerly Clostridium) difficile infection (CDI): Oral: 200 mg twice daily for 10 days. Note: Guidelines recommend fidaxomicin as a treatment option for the initial episode of CDI (non-severe [supportive clinical data: WBC ≤15,000 cells/mm3 and serum creatinine <1.5 mg/dL] and severe [supportive clinical data: WBC >15,000 cells/mm3 and serum creatinine ≥1.5 mg/dL), first recurrence (if vancomycin given for the initial episode), and second or subsequent recurrence. Criteria for disease severity is based on expert opinion and should not replace clinical judgement (IDSA/SHEA [McDonald 2018]).

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Clostridioides (formerly Clostridium) difficile infection (CDI), treatment: Note: Fidaxomicin is only recommended in the setting of multiple recurrences in pediatric patients, as data and experience are limited (IDSA/SHEA [McDonald 2018]). In patients ≥18 years, fidaxomicin is recommended as a first-line treatment option for an initial episode (IDSA/SHEA [McDonald 2018]).

Weight-directed dosing: Limited data available: Infants ≥6 months and Children: Oral: 16 mg/kg/dose twice daily for 10 days; maximum dose: 200 mg/dose (O'Gorman 2018; Wolf 2019). Dosing based on a multi-center, randomized, phase 3 trial comparing fidaxomicin to vancomycin in the treatment of CDI (n=142 [98 received fidaxomicin]; median age: 60 months [interquartile range: 24 to 132 months]); in the trial, patients ≥6 years received a fixed dose of 200 mg twice daily. Most efficacy endpoints, including clinical cure, were statistically similar between treatment groups, with a higher end of study cure rate seen in the fidaxomicin group; adverse events were similar between groups (Wolf 2019).

Fixed dosing: Infants ≥6 months, Children, and Adolescents:

4 to <7 kg: Oral: Oral suspension: 80 mg twice daily for 10 days.

7 to <9 kg: Oral: Oral suspension: 120 mg twice daily for 10 days.

9 to <12.5 kg: Oral: Oral suspension: 160 mg twice daily for 10 days.

≥12.5 kg: Oral: Oral suspension, tablets: 200 mg twice daily for 10 days.


May be administered with or without food.


Store at 20°C to 25°C (68°F to 77°F); excursions permitted to 15°C to 30°C (59°F to 86°F).

Drug Interactions

Lactobacillus and Estriol: Antibiotics may diminish the therapeutic effect of Lactobacillus and Estriol. Monitor therapy

Mizolastine: Macrolide Antibiotics may increase the serum concentration of Mizolastine. Avoid combination

Sodium Picosulfate: Antibiotics may diminish the therapeutic effect of Sodium Picosulfate. Management: Consider using an alternative product for bowel cleansing prior to a colonoscopy in patients who have recently used or are concurrently using an antibiotic. Consider therapy modification

Adverse Reactions

>10%: Gastrointestinal: Nausea (11%)

2% to 10%:

Gastrointestinal: Gastrointestinal hemorrhage (4%), abdominal pain, vomiting

Hematologic & oncologic: Anemia (2%), neutropenia (2%)

<2%, postmarketing, and/or case reports: Abdominal distention, abdominal tenderness, angioedema, decreased platelet count, decreased serum bicarbonate, dyspepsia, dysphagia, dyspnea, fixed drug eruption, flatulence, hepatotoxicity (idiosyncratic) (Chalasani, 2014), hyperglycemia, hypersensitivity reaction, increased liver enzymes, increased serum alkaline phosphatase, intestinal obstruction, megacolon, metabolic acidosis, pruritus, skin rash


Concerns related to adverse effects:

  • Hypersensitivity: Hypersensitivity reactions (angioedema [mouth, face, throat], dyspnea, pruritus, and rash) to fidaxomicin have been reported. If a severe reaction occurs, discontinue drug and institute supportive care.
  • Macrolide allergy: Use with caution in patients with a history of macrolide allergy; may be at increased risk for hypersensitivity.

Other warnings/precautions:

  • Appropriate use: Do not use for systemic infections; fidaxomicin systemic absorption is negligible. Use only in patients with proven or strongly suspected Clostridioides (formerly Clostridium) difficile (C. difficile) infections.


Pregnancy Considerations

The limited systemic absorption of fidaxomicin may limit potential fetal exposure.

Patient Education

What is this drug used for?

  • It is used to treat diarrhea caused by a bacterial infection called C diff.

Frequently reported side effects of this drug

  • Nausea
  • Abdominal pain
  • Vomiting

Other side effects of this drug: Talk with your doctor right away if you have any of these signs of:

  • Shortness of breath
  • Black, tarry, or bloody stools
  • Vomiting blood
  • Chills
  • Severe loss of strength and energy
  • Signs of a significant reaction like wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat.

Note: This is not a comprehensive list of all side effects. Talk to your doctor if you have questions.

Consumer Information Use and Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only the healthcare provider has the knowledge and training to decide which medicines are right for a specific patient. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this medicine. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not specific medical advice and does not replace information you receive from the healthcare provider. You must talk with the healthcare provider for complete information about the risks and benefits of using this medicine.

Source: Wolters Kluwer Health. Last updated February 3, 2020.