Pharmacologic class (EPC) · 3 drug pages

Rifamycin antibacterial: adverse event reports filed with FDA

24,161 reports list a drug in this class as a suspect or interacting product, 2004–2026.

Read first · FDA's statement on these data

Adverse event reports submitted to FDA do not undergo extensive validation or verification. Therefore, a causal relationship cannot be established between product and reactions listed in a report. While a suspected relationship may exist, it is not medically validated and should not be the sole source of information for clinical decision making or other assumptions about the safety or efficacy of a product. Additionally, it is important to remember that adverse event reports represent a small percentage of total usage numbers of a product. Common products may have a higher number of adverse events due to the higher total number of people using the product. openFDA, FDA

FDA adds: "There is no certainty that the reported event (adverse event or medication error) was actually due to the product. FDA does not require that a causal relationship between a product and event be proven, and reports do not always contain enough detail to properly evaluate an event." The information in these reports "cannot be used to estimate the incidence of these events."

Do not rely on openFDA to make decisions regarding medical care. While we make every effort to ensure that data is accurate, you should assume all results are unvalidated.

Not medical advice. This site counts what was reported to FDA. Questions about a medicine or device belong with a pharmacist or clinician.

24,161
reports across the class: 0.1% of all reports; 2,485
reports, 12 months to June 2026: 2,379 in the 12 months before; 80.7%
marked serious by the reporter: 57.4% across all reports; 3
drugs with a page: brand and generic names counted separately

Rifamycin antibacterial is a pharmacologic class (an FDA Established Pharmacologic Class) with 3 drug pages on this site. Together those drugs are listed as a suspect or interacting product in 24,161 adverse event reports received by FDA, 0.1% of the database, from January 2004 to June 2026.

2,485 reports arrived in the 12 months to June 2026, close to the 2,379 of the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. 80.7% of the class's reports are marked serious, 25.4% record death among the outcomes and 37.5% record hospitalisation, as reported.

Across the class the reactions recorded most often are death (16.4%), hospitalisation (7.5%) and drug ineffective (6.5%). The class median share shown beside each term is the middle value across the member drugs; it is the comparison used on every drug page in this class.

The members table is ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Drugs in the class

Drug	Name type	Reports	Latest 12 months	Marked serious	Top term recorded
XifaxanRifaximin	brand	13,995	950	77%	Death
Rifampin	generic	9,224	1,367	84.8%	Drug ineffective
Rifaximin	generic	942	168	95.2%	Drug ineffective

Ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Reports by month, five years

FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.

Reactions recorded across the class

share of class reports recording the termmedian drug in the class

Deaththe patient died; cause not stated by this term16.4%3,965
Hospitalisationadmission to hospital7.5%1,816
Drug ineffectivethe medicine did not work as expected6.5%1,573
Off label useused for a purpose or in a way not on the label6%1,441
Therapy interrupted4.5%1,086
Drug interactionan interaction between medicines4.3%1,036
Diarrhoealoose or frequent stools4%968
Product use in unapproved indicationused for a purpose not on the label4%955
Condition aggravatedthe condition being treated got worse3.8%921
Nauseafeeling sick3.4%824
Ammonia increased3%717
Insurance issue2.9%700
Inability to afford medication2.9%698
Drug reaction with eosinophilia and systemic symptomsDRESS, a severe reaction with rash, fever and organ involvement2.5%602
Confusional stateconfusion2.5%595
Fatiguetiredness2.3%560
Hepatic encephalopathy2.3%560
Vomitingbeing sick2.3%557
Hepatic cirrhosis2.2%535
Product use issuea problem in how the product was used2.1%518
Falla fall1.9%460
Liver disorder1.8%437
Pyrexiafever1.8%433
Drug resistance1.7%403
Dizzinesslight-headedness or unsteadiness1.7%402

Solid bar: share of all class reports. Hollow bar: the median share across the 3 member drugs, the reference used on each member's page. One report can record several terms.

Outcomes, patients and reporters

Outcomes recorded

Death25.4%6,147

Life-threatening3.1%747

Hospitalisation (initial or prolonged)37.5%9,058

Disability1.2%288

Congenital anomaly0.1%35

Other serious36.2%8,747

Not serious19.3%4,663

Patient age

Under 20.6%139

2 to 111.2%284

12 to 171.4%345

18 to 4412.5%3,020

45 to 6422%5,314

65 to 7422.1%5,328

75 and over14.5%3,504

Age not given25.8%6,227

Who reported

Physician19.2%4,642

Pharmacist5.2%1,248

Other health professional25.9%6,251

Lawyer0.1%26

Consumer or non-health professional48.5%11,727

Not given1.1%267

Grey bar: all 20,646,523 reports in the database. Outcome flags are as the reporter set them and are not verified by FDA.

Questions about Rifamycin antibacterial reports

Which drugs are in the Rifamycin antibacterial class on this site?

Xifaxan, Rifampin and Rifaximin. Class membership comes from the pharmacologic class (EPC) on the drug's FDA label.

How many reports does the class have?

24,161 reports through June 2026, 2,485 of them in the latest 12 months. A report listing two drugs of the class counts once for each.

What reactions are recorded most often?

death (16.4%), hospitalisation (7.5%), drug ineffective (6.5%), off label use (6%) and therapy interrupted (4.5%).

Can the members table be used to rank the drugs?

No. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic." Drugs differ in how many people take them, in the conditions they treat, in time on the market and in how diligently reports are collected.

How do I report an adverse event?

Through FDA MedWatch (Form FDA 3500, or 1-800-FDA-1088) or to the manufacturer. See the guide on how to report.

Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A class is the Established Pharmacologic Class most often attached to a drug's reports by openFDA's label harmonisation, or from the NDC Directory where reports carry none. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.

Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.