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Medically reviewed by Last updated on Oct 29, 2020.


(fye DAX oh mye sin)

Index Terms

  • Difimicin
  • Lipiarrmycin
  • OPT-80
  • PAR-101
  • Tiacumicin B

Dosage Forms

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

Tablet, Oral:

Dificid: 200 mg [contains soybean lecithin]

Brand Names: U.S.

  • Dificid

Pharmacologic Category

  • Antibiotic, Macrolide


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)

Special Populations: Elderly

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

Use: Labeled Indications

Clostridioides (formerly Clostridium) difficile infection: Treatment of Clostridioides (formerly Clostridium) difficile infection (CDI) in adult and pediatric patients ≥6 months of age.

Note: The 2017 Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA) guidelines for CDI in adults and children recommend fidaxomicin as a treatment option for the initial episode of CDI (nonsevere 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

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.


Shake bottle to ensure the granules are not caked together. Reconstitute granules for oral suspension with 130 mL purified water. Shake vigorously while bottle is in horizontal position for ≥2 minutes; repeat shaking if not a homogeneous suspension. Once a homogeneous suspension is confirmed, shake for additional 30 seconds. Let bottle stand for 1 minute. If suspension is not homogeneous, shake again. Write discard date (current date plus 12 days) on bottle.


Oral: May be administered with or without food.

Suspension: Remove from refrigerator 15 minutes prior to each administration. Shake vigorously before use; use oral dosing syringe for administration.


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).

Suspension: Store reconstituted oral suspension at 2°C to 8°C (36°F to 46°F) for ≤12 days; discard after 12 days. Do not open pouch until time of use; store in original bottle.

Drug Interactions

Cholera Vaccine: Antibiotics may diminish the therapeutic effect of Cholera Vaccine. Management: Avoid cholera vaccine in patients receiving systemic antibiotics, and within 14 days following the use of oral or parenteral antibiotics. Avoid combination

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

Typhoid Vaccine: Antibiotics may diminish the therapeutic effect of Typhoid Vaccine. Only the live attenuated Ty21a strain is affected. Management: Avoid use of live attenuated typhoid vaccine (Ty21a) in patients being treated with systemic antibacterial agents. Postpone vaccination until 3 days after cessation of antibiotics and avoid starting antibiotics within 3 days of last vaccine dose. Consider therapy modification

Adverse Reactions

The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified.


Gastrointestinal: Nausea (adults 11%)

Miscellaneous: Fever (infants, children, and adolescents: 13%)

1% to 10%:

Dermatologic: Pruritus (<5%), skin rash (adults: <2%), urticaria (infants, children, and adolescents: <5%)

Endocrine & metabolic: Decreased serum bicarbonate (adults: <2%), hyperglycemia (adults: <2%), metabolic acidosis (adults: <2%)

Gastrointestinal: Abdominal distention (adults: <2%), abdominal pain (6% to 8%), abdominal tenderness (adults: <2%), constipation (infants, children, and adolescents: 5%), diarrhea (infants, children, and adolescents: 7%), dyspepsia (adults: <2%), dysphagia (adults: <2%), flatulence (adults: <2%), gastrointestinal hemorrhage (adults: 4%), intestinal obstruction (adults: <2%), non-Hirschsprung megacolon (adults: <2%), vomiting (7%)

Hematologic & oncologic: Anemia (adults: 2%), decreased platelet count (adults: <2%), neutropenia (adults: 2%)

Hepatic: Increased liver enzymes (adults: ≤5%), increased serum alkaline phosphatase (adults: <2%), increased serum transaminases (infants, children, and adolescents: 5%)

Hypersensitivity: Fixed drug eruption (adults: <2%)


Hepatic: Hepatotoxicity (idiosyncratic) (Chalasani 2014)

Hypersensitivity: Angioedema, hypersensitivity reaction


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.

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

• Nausea

• Diarrhea

• Constipation

• Abdominal pain

• Vomiting

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

• Shortness of breath

• Black, tarry, or bloody stools

• Vomiting blood

• Chills

• Severe loss of strength and energy

• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, 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 limited summary of general information about the medicine's uses from the patient education leaflet and is not intended to be comprehensive. This limited summary does NOT include all information available about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not intended to provide medical advice, diagnosis or treatment and does not replace information you receive from the healthcare provider. For a more detailed summary of information about the risks and benefits of using this medicine, please speak with your healthcare provider and review the entire patient education leaflet.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.