Dificid (fidaxomicin) is a macrolide antibacterial drug developed by Merck & Co., Inc. It was approved for marketing by the U.S. FDA in 2011. As a narrow-spectrum antibacterial agent, fidaxomicin specifically inhibits the RNA synthesis of Clostridioides difficile and is used for the treatment of Clostridioides difficile-associated diarrhea (CDAD).

What Kind of Drug Is Dificid (Fidaxomicin)?

Main Indications

Fidaxomicin is a macrolide antibacterial drug, indicated for the treatment of Clostridioides difficile-associated diarrhea (CDAD) caused by Clostridioides difficile.

For adult patients.

For pediatric patients aged 6 months and older.

Key Notes

Laboratory Confirmation Required: It is recommended to use the drug only after a clear diagnosis is made through stool testing (e.g., Clostridioides difficile toxin A/B test).

Not for Infants Under 6 Months Old: Efficacy has not been established in this age group.

Dosage Form, Strength and Characteristics of Dificid (Fidaxomicin)

Drug Composition and Dosage Form

Tablets: Each tablet contains 200 mg of fidaxomicin. They are white to off-white film-coated tablets, engraved with "FDX" on one side and "200" on the other side.

Oral Suspension: It is white to yellowish-white granules. After reconstitution, the concentration is 40 mg/mL (200 mg/5 mL). It needs to be stored under refrigeration and used up within 12 days.

Excipient Composition

Tablets contain excipients such as hydroxypropyl cellulose and magnesium stearate.

The oral suspension contains flavoring agents and stabilizers such as citric acid and mixed berry flavor.

Storage Conditions

Tablets should be stored at room temperature (20°C-25°C).

After reconstitution, the oral suspension should be refrigerated (2°C-8°C) and discarded after 12 days.

Usage and Dosage of Dificid (Fidaxomicin)

Adult Administration

The recommended dosage is 200 mg (one tablet) taken orally twice daily for a 10-day course of treatment. It can be taken with food or on an empty stomach.

Pediatric Administration

Pediatric patients ≥12.5 kg who can swallow tablets: Same dosage as adults.

Pediatric patients 4 kg to <12.5 kg: The oral suspension is required, and the dosage is adjusted based on body weight:

4 kg to <7 kg: 80 mg per dose (2 mL of the reconstituted suspension)

7 kg to <9 kg: 120 mg per dose (3 mL of the reconstituted suspension)

9 kg to <12.5 kg: 160 mg per dose (4 mL of the reconstituted suspension)

≥12.5 kg: 200 mg per dose (5 mL of the reconstituted suspension)

Reconstitution Method for Oral Suspension

Add 130 mL of purified water, shake vigorously for 2 minutes, let it stand for 1 minute, then shake again for 30 seconds. The reconstituted suspension is a white to yellowish-white homogeneous liquid.