Drug · FAERS side-effect profile with label screen
Fidaxomicin side effects: what 2,385 FDA adverse event reports show
Drug class
Macrolide Antibacterial
FDA label (Established Pharmacologic Class)
Brand names
Dificid
openFDA label
Who reports
2,385 reports · 59% serious · 257 with death outcome · 62% female
openFDA FAERS counts, all years, deduplication not applied
Used for
DIFICID is a macrolide antibacterial indicated in adult and pediatric patients 6 months of age and older for the treatment of C. difficile -associated diarrhea. ( 1.1 ) To reduce the development of drug-resistant bacteria and maintain the effectiveness of DIFICID and other antibacterial drugs, DIFICID should be used only to treat infections that are proven or strongly suspected to be caused by C. difficile .
FDA label, Indications and Usage
What it is
DIFICID (fidaxomicin) is a macrolide antibacterial drug for oral administration. Its CAS chemical name is Oxacyclooctadeca-3,5,9,13,15-pentaen-2-one, 3-[[[6-deoxy-4- O -(3,5-dichloro-2-ethyl-4.
FDA label, Description section
Boxed warning
None in the current label
How to read this page. FAERS is a spontaneous-reporting system: counts are not incidence rates and a signal is not proof of causation.
Each reaction below is run through an automated screen — is the term in the FDA label (known), in the indications (the disease being treated), an administrative/coding term, or none of these (unlabeled)?
That screen is mechanical text matching, not a causality assessment. The 30 hand-written Bradford Hill assessments are on the causality assessment page. Not medical advice.
Causality screen of the 39 strongest signals
Labeled adverse reaction 2Labeled (related wording) 3Likely indication confounding 1Reporting / coding artifact 10Lab value / disease marker 1Not in label — unassessed 22
What the badges mean
- Labeled adverse reaction The exact term appears in the label's warnings or adverse-reactions sections: a known, expected effect. The FAERS signal confirms the label rather than discovering anything.
- Labeled (related wording) The label describes this effect under different wording (e.g. 'neutropenia' for 'neutrophil count decreased'). Treated as known.
- Likely indication confounding The term appears in the label's indications: reports probably describe the disease being treated (or its progression), not a drug effect. Classic confounding by indication.
- Reporting / coding artifact An administrative, monitoring or exposure term (product issue, off-label use, 'test normal', overdose...). Not a biological reaction; a high PRR here reflects how reports are coded.
- Lab value / disease marker A laboratory result, investigation or disease-activity marker (antibody positive, CRP abnormal, swollen joint count) not described in the label. These usually mirror the monitored disease or testing protocol rather than a drug effect; not screened further.
- Not in label — unassessed Not found in the label text, not an artifact pattern. This is a genuine candidate for a formal causality assessment (Bradford Hill / WHO-UMC); it has NOT had one here.
Strongest disproportionality signals
Flagged terms (PRR ≥ 2, χ² ≥ 4, n ≥ 10), ranked by PRR; infinite PRRs (no comparator reports) excluded. The EBGM column is a second, shrinkage-based estimate (MGPS) with its 5th percentile EB05 and the BCPNN IC025; a pair flagged by PRR alone is marked PRR-only and should be read as fragile. The strata column recomputes the PRR on serious reports only and flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 23 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.
Show:
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Clostridium difficile infection | 480 | 199.2 183.7–216.0ROR 249.1 · χ² 92,423 / p <1e-300 | 193.2 EB05 179.2 · IC025 +7.2 3/3 methods agree | Labeled (related wording) related wording | serious PRR 163.2 | no trial data cached |
| Clostridium difficile colitis | 161 | 135.4 116.5–157.3ROR 145.1 · χ² 21,020 / p <1e-300 | 131.2 EB05 115.1 · IC025 +6.3 3/3 methods agree | Labeled (related wording) related wording | serious PRR 88.5 | no trial data cached |
| Disease recurrence | 179 | 33.1 28.7–38.1ROR 35.7 · χ² 5,532 / p <1e-300 | 32.9 EB05 29.0 · IC025 +4.7 3/3 methods agree | Reporting / coding artifact | serious PRR 21.2 | no trial data cached |
| Product packaging quantity issue | 29 | 23.4 16.3–33.6ROR 23.7 · χ² 599 / p 1e-132 | 23.0 EB05 16.8 · IC025 +3.5 3/3 methods agree | Reporting / coding artifact | serious n=2 | no trial data cached |
| Product prescribing issue | 33 | 14.3 10.2–20.0ROR 14.5 · χ² 394 / p 5e-88 | 14.0 EB05 10.2 · IC025 +3.0 3/3 methods agree | Reporting / coding artifact | serious PRR 8.8 | no trial data cached |
| Agranulocytosis (severe loss of white cells) | 29 | 13.8 9.6–19.8ROR 14.0 · χ² 332 / p 2e-74 | 13.4 EB05 9.5 · IC025 +2.9 3/3 methods agree | Labeled (related wording) related wording | serious PRR 13.4 · ♀ 10% (drug 62%) | no trial data cached |
| Treatment failure | 119 | 12.8 10.7–15.2ROR 13.4 · χ² 1,282 / p 6e-281 | 12.7 EB05 10.8 · IC025 +3.3 3/3 methods agree | Reporting / coding artifact | serious PRR 9.2 | no trial data cached |
| Melaena (black stool) | 28 | 11.2 7.7–16.1ROR 11.3 · χ² 249 / p 2e-56 | 10.5 EB05 7.4 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious PRR 10.6 · ♀ 30% (drug 62%) · 93% clinician | no trial data cached |
| Pneumonia aspiration | 31 | 10.9 7.7–15.5ROR 11.1 · χ² 270 / p 5e-61 | 10.3 EB05 7.4 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious PRR 10.6 · 94% clinician | no trial data cached |
| Hepatic cytolysis | 15 | 10.8 6.5–17.9ROR 10.9 · χ² 124 / p 5e-29 | 9.4 EB05 5.6 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious PRR 9.8 | no trial data cached |
| Incorrect product administration duration | 24 | 10.4 7.0–15.5ROR 10.5 · χ² 195 / p 1e-44 | 9.6 EB05 6.5 · IC025 +2.4 3/3 methods agree | Reporting / coding artifact | serious n=14 | no trial data cached |
| Poor quality product administered | 12 | 10.3 5.9–18.2ROR 10.4 · χ² 92 / p 4e-22 | 8.6 EB05 4.8 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | – | no trial data cached |
| Gastroenteritis | 17 | 10.3 6.4–16.5ROR 10.3 · χ² 133 / p 5e-31 | 9.0 EB05 5.6 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious PRR 10.7 | no trial data cached |
| Drug resistance | 28 | 9.6 6.6–13.9ROR 9.7 · χ² 207 / p 3e-47 | 8.8 EB05 6.2 · IC025 +2.4 3/3 methods agree | Reporting / coding artifact | serious PRR 9.7 · ♀ 27% (drug 62%) | no trial data cached |
| Septic shock | 46 | 9.4 7.0–12.5ROR 9.5 · χ² 336 / p 3e-75 | 8.9 EB05 6.8 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious PRR 9.1 · ♀ 40% (drug 62%) | no trial data cached |
| Inability to afford medication | 10 | 8.9 4.8–16.6ROR 9.0 · χ² 63 / p 1e-15 | 7.0 EB05 3.9 · IC025 +1.6 3/3 methods agree | Not in label — unassessed | serious n=4 | no trial data cached |
| Adrenal insufficiency | 11 | 8.1 4.5–14.6ROR 8.1 · χ² 61 / p 2e-15 | 6.4 EB05 3.7 · IC025 +1.6 3/3 methods agree | Not in label — unassessed | serious PRR 7.9 | no trial data cached |
| Cytomegalovirus infection | 15 | 7.9 4.8–13.1ROR 8.0 · χ² 84 / p 2e-20 | 6.7 EB05 4.2 · IC025 +1.8 3/3 methods agree | Not in label — unassessed | serious PRR 7.8 | no trial data cached |
| Drug reaction with eosinophilia and systemic symptoms | 22 | 7.6 5.0–11.5ROR 7.6 · χ² 119 / p 5e-28 | 6.7 EB05 4.6 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 7.3 · 100% clinician | no trial data cached |
| White blood cell count increased | 30 | 6.9 4.8–9.8ROR 6.9 · χ² 144 / p 1e-33 | 6.3 EB05 4.6 · IC025 +2.0 3/3 methods agree | Lab value / disease marker | serious PRR 3.7 · ♀ 40% (drug 62%) · 83% consumer | no trial data cached |
| Oral candidiasis (oral thrush) | 10 | 6.8 3.6–12.6ROR 6.8 · χ² 43 / p 2e-11 | 5.3 EB05 3.1 · IC025 +1.3 3/3 methods agree | Not in label — unassessed | serious PRR 9.2 | no trial data cached |
| Leukocytosis | 13 | 6.3 3.7–10.9ROR 6.4 · χ² 53 / p 2e-13 | 5.3 EB05 3.3 · IC025 +1.5 3/3 methods agree | Not in label — unassessed | serious PRR 6.3 | no trial data cached |
| Hypoxia (low oxygen) | 24 | 6.0 4.0–9.0ROR 6.1 · χ² 96 / p 7e-23 | 5.4 EB05 3.8 · IC025 +1.8 3/3 methods agree | Not in label — unassessed | serious PRR 5.9 · ♀ 14% (drug 62%) · 92% clinician | no trial data cached |
| Rash maculo-papular | 15 | 6.0 3.6–9.9ROR 6.0 · χ² 57 / p 2e-14 | 5.1 EB05 3.3 · IC025 +1.5 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 5.5 | no trial data cached |
| Device related infection | 10 | 5.7 3.1–10.6ROR 5.7 · χ² 34 / p 2e-9 | 4.6 EB05 2.7 · IC025 +1.1 3/3 methods agree | Reporting / coding artifact | serious PRR 5.7 | no trial data cached |
| Colitis | 22 | 5.1 3.4–7.8ROR 5.2 · χ² 69 / p 4e-17 | 4.7 EB05 3.3 · IC025 +1.5 3/3 methods agree | Not in label — unassessed | serious PRR 5.1 | no trial data cached |
| Cholestasis (bile flow blockage) | 11 | 5.1 2.8–9.1ROR 5.1 · χ² 32 / p 8e-9 | 4.3 EB05 2.6 · IC025 +1.1 3/3 methods agree | Not in label — unassessed | serious PRR 5.0 | no trial data cached |
| Product dispensing error | 12 | 4.9 2.8–8.5ROR 4.9 · χ² 33 / p 5e-9 | 4.2 EB05 2.6 · IC025 +1.1 3/3 methods agree | Reporting / coding artifact | serious n=2 | no trial data cached |
| Diarrhoea (diarrhea) | 350 | 4.8 4.3–5.3ROR 5.4 · χ² 1,077 / p 2e-236 | 4.8 EB05 4.4 · IC025 +2.1 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious PRR 4.0 | no trial data cached |
| Peritonitis | 11 | 4.7 2.6–8.4ROR 4.7 · χ² 28 / p 6e-8 | 4.0 EB05 2.4 · IC025 +1.0 3/3 methods agree | Not in label — unassessed | serious PRR 4.5 | no trial data cached |
| Faeces discoloured | 11 | 4.5 2.5–8.0ROR 4.5 · χ² 26 / p 2e-7 | 3.8 EB05 2.3 · IC025 +0.9 3/3 methods agree | Not in label — unassessed | serious PRR 4.2 | no trial data cached |
| Pancytopenia (all blood cells low) | 28 | 4.4 3.1–6.4ROR 4.5 · χ² 71 / p 2e-17 | 4.1 EB05 3.0 · IC025 +1.4 3/3 methods agree | Not in label — unassessed | serious PRR 4.3 | no trial data cached |
| Multiple organ dysfunction syndrome | 14 | 4.4 2.6–7.4ROR 4.4 · χ² 34 / p 3e-9 | 3.9 EB05 2.5 · IC025 +1.1 3/3 methods agree | Not in label — unassessed | serious PRR 4.3 | no trial data cached |
| Flatulence (gas) | 28 | 4.4 3.0–6.3ROR 4.4 · χ² 69 / p 5e-17 | 4.1 EB05 3.0 · IC025 +1.4 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.4 · ♀ 90% (drug 62%) | no trial data cached |
| No adverse event | 86 | 4.3 3.5–5.2ROR 4.4 · χ² 213 / p 1e-48 | 4.2 EB05 3.5 · IC025 +1.7 3/3 methods agree | Reporting / coding artifact | – | no trial data cached |
| Hyperkalaemia (high potassium) | 16 | 4.0 2.5–6.6ROR 4.1 · χ² 34 / p 3e-9 | 3.7 EB05 2.4 · IC025 +1.0 3/3 methods agree | Not in label — unassessed | serious PRR 4.0 | no trial data cached |
| Product availability issue | 10 | 3.9 2.1–7.3ROR 3.9 · χ² 19 / p 7e-6 | 3.4 EB05 2.0 · IC025 +0.7 3/3 methods agree | Reporting / coding artifact | serious PRR 6.3 | no trial data cached |
| Frequent bowel movements | 11 | 3.6 2.0–6.5ROR 3.6 · χ² 18 / p 1e-5 | 3.2 EB05 1.9 · IC025 +0.7 | Not in label — unassessed | serious PRR 2.0 | no trial data cached |
| Colitis ulcerative | 17 | 3.4 2.1–5.4ROR 3.4 · χ² 26 / p 2e-7 | 3.1 EB05 2.1 · IC025 +0.8 3/3 methods agree | Not in label — unassessed | serious PRR 3.3 | no trial data cached |
Trial evidence (ClinicalTrials.gov)
Trial cross-check not yet run for this drug (ClinicalTrials.gov pull covers the 800 most-reported drugs first).
Most frequently reported reactions
By raw co-report count, regardless of disproportionality. Common terms here are often the illness itself or generic outcomes.
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Clostridium difficile infection | 480 | 199.2 183.7–216.0ROR 249.1 · χ² 92,423 / p <1e-300 | 193.2 EB05 179.2 · IC025 +7.2 3/3 methods agree | Labeled (related wording) related wording | serious PRR 163.2 | no trial data cached |
| Diarrhoea (diarrhea) | 350 | 4.8 4.3–5.3ROR 5.4 · χ² 1,077 / p 2e-236 | 4.8 EB05 4.4 · IC025 +2.1 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious PRR 4.0 | no trial data cached |
| Disease recurrence | 179 | 33.1 28.7–38.1ROR 35.7 · χ² 5,532 / p <1e-300 | 32.9 EB05 29.0 · IC025 +4.7 3/3 methods agree | Reporting / coding artifact | serious PRR 21.2 | no trial data cached |
| Clostridium difficile colitis | 161 | 135.4 116.5–157.3ROR 145.1 · χ² 21,020 / p <1e-300 | 131.2 EB05 115.1 · IC025 +6.3 3/3 methods agree | Labeled (related wording) related wording | serious PRR 88.5 | no trial data cached |
| Treatment failure | 119 | 12.8 10.7–15.2ROR 13.4 · χ² 1,282 / p 6e-281 | 12.7 EB05 10.8 · IC025 +3.3 3/3 methods agree | Reporting / coding artifact | serious PRR 9.2 | no trial data cached |
| No adverse event | 86 | 4.3 3.5–5.2ROR 4.4 · χ² 213 / p 1e-48 | 4.2 EB05 3.5 · IC025 +1.7 3/3 methods agree | Reporting / coding artifact | – | no trial data cached |
| Septic shock | 46 | 9.4 7.0–12.5ROR 9.5 · χ² 336 / p 3e-75 | 8.9 EB05 6.8 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious PRR 9.1 · ♀ 40% (drug 62%) | no trial data cached |
| Product prescribing issue | 33 | 14.3 10.2–20.0ROR 14.5 · χ² 394 / p 5e-88 | 14.0 EB05 10.2 · IC025 +3.0 3/3 methods agree | Reporting / coding artifact | serious PRR 8.8 | no trial data cached |
| Pneumonia aspiration | 31 | 10.9 7.7–15.5ROR 11.1 · χ² 270 / p 5e-61 | 10.3 EB05 7.4 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious PRR 10.6 · 94% clinician | no trial data cached |
| White blood cell count increased | 30 | 6.9 4.8–9.8ROR 6.9 · χ² 144 / p 1e-33 | 6.3 EB05 4.6 · IC025 +2.0 3/3 methods agree | Lab value / disease marker | serious PRR 3.7 · ♀ 40% (drug 62%) · 83% consumer | no trial data cached |
| Agranulocytosis (severe loss of white cells) | 29 | 13.8 9.6–19.8ROR 14.0 · χ² 332 / p 2e-74 | 13.4 EB05 9.5 · IC025 +2.9 3/3 methods agree | Labeled (related wording) related wording | serious PRR 13.4 · ♀ 10% (drug 62%) | no trial data cached |
| Product packaging quantity issue | 29 | 23.4 16.3–33.6ROR 23.7 · χ² 599 / p 1e-132 | 23.0 EB05 16.8 · IC025 +3.5 3/3 methods agree | Reporting / coding artifact | serious n=2 | no trial data cached |
| Flatulence (gas) | 28 | 4.4 3.0–6.3ROR 4.4 · χ² 69 / p 5e-17 | 4.1 EB05 3.0 · IC025 +1.4 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 2.4 · ♀ 90% (drug 62%) | no trial data cached |
| Pancytopenia (all blood cells low) | 28 | 4.4 3.1–6.4ROR 4.5 · χ² 71 / p 2e-17 | 4.1 EB05 3.0 · IC025 +1.4 3/3 methods agree | Not in label — unassessed | serious PRR 4.3 | no trial data cached |
| Drug resistance | 28 | 9.6 6.6–13.9ROR 9.7 · χ² 207 / p 3e-47 | 8.8 EB05 6.2 · IC025 +2.4 3/3 methods agree | Reporting / coding artifact | serious PRR 9.7 · ♀ 27% (drug 62%) | no trial data cached |
Unlabeled candidate signals
These flagged terms were not found in the FDA label text and do not match an artifact pattern. They are the pairs that would merit a structured assessment (temporality, dose-response, biological plausibility, consistency across databases, trial or cohort evidence). The screen has not done that; string-matching misses label wording, and a strong PRR can still be stimulated reporting, co-medication, or the disease itself.
- Melaena — n=28, PRR 11.2
- Pneumonia aspiration — n=31, PRR 10.9
- Septic shock — n=46, PRR 9.4
- Drug reaction with eosinophilia and systemic symptoms — n=22, PRR 7.6
- Hypoxia — n=24, PRR 6.0
- Colitis — n=22, PRR 5.1
- Pancytopenia — n=28, PRR 4.4
Want to assess one of these properly? The runbook describes the Bradford Hill / trial-evidence workflow used on the assessment page, and handoff_top1000_signals.csv lists the strongest unassessed pairs across all drugs.
Common questions
What are the most reported side effects of Fidaxomicin?
In FDA FAERS, the most frequently co-reported reaction terms for Fidaxomicin are clostridium difficile infection, diarrhoea, clostridium difficile colitis, septic shock, pneumonia aspiration, white blood cell count increased. These are report counts, not rates: FAERS has no denominator, reporting is voluntary and uneven, and a term can be reported because of the illness being treated rather than the drug.
Does Fidaxomicin have an FDA boxed warning?
No. The FDA label retrieved for Fidaxomicin has no boxed warning; see the label's Warnings and Precautions for the recognised risks.
Do FAERS signals prove that Fidaxomicin causes these side effects?
No. A disproportionality signal (PRR, ROR) means a reaction is reported more often with this drug than with others in the database. That can reflect a real effect, but also the disease being treated, stimulated reporting after news or litigation, co-medications, or how reports are coded. Causality needs temporality, dose-response, biological plausibility, consistency across data sources and, ideally, trial or cohort evidence. This page screens each term against the FDA label and ClinicalTrials.gov results; it does not establish causation.
Sources & methods
- FDA label via openFDA (set ID dd966338-c820-4270-b704-09ef75fa3ceb, effective 20241016; matched on
openfda.generic_name.exact:"FIDAXOMICIN") - Bayesian shrinkage measures computed offline over all 1,317,300 cached pairs: BCPNN information component (IC, with Norén closed-form IC025) and MGPS empirical-Bayes geometric mean (EBGM, EB05) with a two-component gamma prior fitted by maximum marginal likelihood (α₁=0.57, β₁=0.02, α₂=1.42, β₂=0.70, w=0.17); unstratified
- FAERS pair statistics from the OpenPV build of 2026-09-14 (openFDA
count=aggregation, fieldpatient.drug.openfda.generic_name.exact, 62 reaction terms, min 3 co-reports); PRR/ROR with 95% CI, chi-square with Yates correction - Serious-only and stratified counts (serious:1, patient.patientsex, primarysource.qualification) from openFDA count queries; serious-only PRR uses the drug serious report total and the term global serious total (N_serious=11,882,979); strata shown only when n ≥ 20
- Seriousness and sex counts from openFDA
count=serious,patient.patientsex,seriousnessdeath
Page generated 2026-10-08. Label and PubChem text are retrieved automatically and may lag the current label; always check the current prescribing information. OpenPV is a beta research tool of the Open Source Medicine Foundation.