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Medically reviewed on Nov 15, 2018


(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

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

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

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: Renal Impairment

No dosage adjustment necessary (minimal systemic absorption).

Dosing: Hepatic Impairment

There are no dosage adjustments provided in the manufacturer’s label (has not been studied); However, due to minimal systemic absorption no dosage adjustment predicted.


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 Risk Factor


Pregnancy Considerations

Adverse events were not observed in animal reproduction studies. Due to the limited systemic absorption of fidaxomicin, exposure to the fetus is expected to be low.

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience nausea or vomiting. Have patient report immediately to prescriber black, tarry, or bloody stools; vomiting blood; chills; pharyngitis; severe constipation; severe abdominal pain, or severe loss of strength and energy (HCAHPS).

• Educate patient about signs of a significant reaction (eg, 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. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.

Further information

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