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Side Effects


Clinical Studies Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Travelers' Diarrhea

The safety of XIFAXAN 200 mg taken three times a day was evaluated in patients with travelers' diarrhea consisting of 320 patients in two placebo-controlled clinical trials with 95% of patients receiving three or four days of treatment with XIFAXAN. The population studied had a mean age of 31.3 (18-79) years of which approximately 3% were ≥ 65 years old, 53% were male and 84% were White, 11% were Hispanic.

Discontinuations due to adverse reactions occurred in 0.4% of patients. The adverse reactions leading to discontinuation were taste loss, dysentery, weight decrease, anorexia, nausea and nasal passage irritation.

All adverse reactions for XIFAXAN 200 mg three times daily that occurred at a frequency ≥ 2% in the two placebo-controlled trials combined are provided in Table 1. (These include adverse reactions that may be attributable to the underlying disease.)

Table 1: All Adverse Reactions With an Incidence ≥ 2% Among Patients Receiving XIFAXAN Tablets, 200 mg Three Times Daily, in Placebo-Controlled Studies

MedDRA Preferred Term Number (%) of Patients
XIFAXAN Tablets, 600 mg/day
N = 320
N = 228
Flatulence 36 (11%) 45 (20%)
Headache 31 (10%) 21 (9%)
Abdominal Pain NOS* 23 (7%) 23 (10%)
Rectal Tenesmus 23 (7%) 20 (9%)
Defecation Urgency 19 (6%) 21 (9%)
Nausea 17 (5%) 19 (8%)
Constipation 12 (4%) 8 (4%)
Pyrexia 10 (3%) 10 (4%)
Vomiting NOS 7 (2%) 4 (2%)
*NOS: Not otherwise specified

The following adverse reactions, presented by body system, have also been reported in < 2% of patients taking XIFAXAN in the two placebo-controlled clinical trials where the 200 mg tablet was taken three times a day for travelers' diarrhea. The following includes adverse reactions regardless of causal relationship to drug exposure.

Blood and Lymphatic System Disorders: Lymphocytosis, monocytosis, neutropenia

Ear and Labyrinth Disorders: Ear pain, motion sickness, tinnitus

Gastrointestinal Disorders: Abdominal distension, diarrhea NOS, dry throat, fecal abnormality NOS, gingival disorder NOS, inguinal hernia NOS, dry lips, stomach discomfort

General Disorders and Administration Site Conditions: Chest pain, fatigue, malaise, pain NOS, weakness

Infections and Infestations: Dysentery NOS, respiratory tract infection NOS, upper respiratory tract infection NOS

Injury and Poisoning: Sunburn

Investigations: Aspartate aminotransferase increased, blood in stool, blood in urine, weight decreased

Metabolic and Nutritional Disorders: Anorexia, dehydration

Musculoskeletal, Connective Tissue, and Bone Disorders: Arthralgia, muscle spasms, myalgia, neck pain

Nervous System Disorders: Abnormal dreams, dizziness, migraine NOS, syncope, loss of taste

Psychiatric Disorders: Insomnia

Renal and Urinary Disorders: Choluria, dysuria, hematuria, polyuria, proteinuria, urinary frequency

Respiratory, Thoracic, and Mediastinal Disorders: Dyspnea NOS, nasal passage irritation, nasopharyngitis, pharyngitis, pharyngolaryngeal pain, rhinitis NOS, rhinorrhea

Skin and Subcutaneous Tissue Disorders: Clamminess, rash NOS, sweating increased

Vascular Disorders: Hot flashes NOS

Hepatic Encephalopathy

The data described below reflect exposure to XIFAXAN 550 mg in 348 patients, including 265 exposed for 6 months and 202 exposed for more than a year (mean exposure was 364 days). The safety of XIFAXAN 550 mg taken two times a day for reducing the risk of overt hepatic encephalopathy recurrence in adult patients was evaluated in a 6-month placebo-controlled clinical trial (n = 140) and in a long term follow-up study (n = 280). The population studied had a mean age of 56.26 (range: 21-82) years; approximately 20% of the patients were ≥ 65 years old, 61% were male, 86% were White, and 4% were Black. Ninety-one percent of patients in the trial were taking lactulose concomitantly. All adverse reactions that occurred at an incidence ≥ 5% and at a higher incidence in XIFAXAN 550 mg-treated subjects than in the placebo group in the 6-month trial are provided in Table 2. (These include adverse events that may be attributable to the underlying disease).

Table 2: Adverse Reactions Occurring in ≥ 5% of Patients Receiving XIFAXAN and at a Higher Incidence Than Placebo

MedDRA Preferred Term Number (%) of Patients
N = 140
N = 159
Edema peripheral 21 (15%) 13 (8%)
Nausea 20 (14%) 21 (13%)
Dizziness 18 (13%) 13 (8%)
Fatigue 17 (12%) 18 (11%)
Ascites 16 (11%) 15 (9%)
Muscle spasms 13 (9%) 11 (7%)
Pruritus 13 (9%) 10 (6%)
Abdominal pain 12 (9%) 13 (8%)
Abdominal distension 11 (8%) 12 (8%)
Anemia 11 (8%) 6 (4%)
Cough 10 (7%) 11 (7%)
Depression 10 (7%) 8 (5%)
Insomnia 10 (7%) 11 (7%)
Nasopharyngitis 10 (7%) 10 (6%)
Abdominal pain upper 9 (6%) 8 (5%)
Arthralgia 9 (6%) 4 (3%)
Back pain 9 (6%) 10 (6%)
Constipation 9 (6%) 10 (6%)
Dyspnea 9 (6%) 7 (4%)
Pyrexia 9 (6%) 5 (3%)
Rash 7 (5%) 6 (4%)

The following adverse reactions, presented by body system, have also been reported in the placebo-controlled clinical trial in greater than 2% but less than 5% of patients taking XIFAXAN 550 mg taken orally two times a day for hepatic encephalopathy. The following includes adverse events occurring at a greater incidence than placebo, regardless of causal relationship to drug exposure.

Ear and Labyrinth Disorders: Vertigo

Gastrointestinal Disorders: Abdominal pain lower, abdominal tenderness, dry mouth, esophageal variceal bleed, stomach discomfort

General Disorders and Administration Site Conditions: Chest pain, generalized edema, influenza like illness, pain NOS

Infections and Infestations: Cellulitis, pneumonia, rhinitis, upper respiratory tract infection NOS

Injury, Poisoning and Procedural Complications: Contusion, fall, procedural pain

Investigations: Weight increased

Metabolic and Nutritional Disorders: Anorexia, dehydration, hyperglycemia, hyperkalemia, hypoglycemia, hyponatremia

Musculoskeletal, Connective Tissue, and Bone Disorders: Myalgia, pain in extremity

Nervous System Disorders: Amnesia, disturbance in attention, hypoesthesia, memory impairment, tremor

Psychiatric Disorders: Confusional state

Respiratory, Thoracic, and Mediastinal Disorders: Epistaxis

Vascular Disorders: Hypotension

Postmarketing Experience

The following adverse reactions have been identified during post approval use of XIFAXAN. Because these reactions are reported voluntarily from a population of unknown size, estimates of frequency cannot be made. These reactions have been chosen for inclusion due to either their seriousness, frequency of reporting or causal connection to XIFAXAN.

Infections and Infestations

Cases of C. difficile-associated colitis have been reported [see WARNINGS AND PRECAUTIONS].


Hypersensitivity reactions, including exfoliative dermatitis, rash, angioneurotic edema (swelling of face and tongue and difficulty swallowing), urticaria, flushing, pruritus and anaphylaxis have been reported. These events occurred as early as within 15 minutes of drug administration.

Read the Xifaxan (rifaximin) Side Effects Center for a complete guide to possible side effects


Effects Of Rifaximin On Cytochrome P450 Enzymes

In vitro studies have shown that rifaximin did not inhibit cytochrome P450 isoenzymes 1A2, 2A6, 2B6, 2C9, 2C19, 2D6, 2E1 and CYP3A4 at concentrations ranging from 2 to 200 ng/mL [see CLINICAL PHARMACOLOGY]. Rifaximin is not expected to inhibit these enzymes in clinical use. An in vitro study has suggested that rifaximin induces CYP3A4 [see CLINICAL PHARMACOLOGY]. However, in patients with normal liver function, rifaximin at the recommended dosing regimen is not expected to induce CYP3A4. It is unknown whether rifaximin can have a significant effect on the pharmacokinetics of concomitant CYP3A4 substrates in patients with reduced liver function who have elevated rifaximin concentrations.

Concomitant P-glycoprotein Inhibitors

An in vitro study suggested that rifaximin is a substrate of P-glycoprotein. Co-administration of cyclosporine, a potent P-glycoprotein inhibitor, with rifaximin resulted in 83-fold and 124-fold increases in rifaximin mean Cmax and AUC∞ in healthy subjects. The clinical significance of this increase in systemic exposure is unknown [see CLINICAL PHARMACOLOGY].

Read the Xifaxan Drug Interactions Center for a complete guide to possible interactions

Last reviewed on RxList: 3/28/2014
This monograph has been modified to include the generic and brand name in many instances.

Side Effects

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