Rifaximin

Rifaximin tab: May be taken with or without food.

Hypersensitivity. Intestinal obstruction.

Not indicated as treatment of Traveller's diarrhoea that is complicated by fever, blood in stool, ≥8 unformed stools in the previous 24 hours, or occult blood or leucocytes in the stool. Not indicated for the treatment of systemic infections. Renal and hepatic impairment. Children. Pregnancy and lactation.

Significant: Clostridioides difficile-associated diarrhoea, pseudomembranous colitis, reddish discolouration of the urine.
Blood and lymphatic system disorders: Anaemia, lymphocytosis, monocytosis, neutropenia.
Cardiac disorders: Palpitations.
Ear and labyrinth disorders: Ear pain, vertigo.
Eye disorders: Diplopia.
Gastrointestinal disorders: Diarrhoea, abdominal pain, constipation, defaecation urgency, flatulence, abdominal distension, nausea, vomiting, rectal tenesmus, dry lips, dyspepsia, gastrointestinal motility disorder, hard faeces, haematochezia, mucous stools, taste disorders.
General disorders and administration site conditions: Pyrexia, peripheral oedema, fatigue, asthenic conditions, chills, cold sweat, influenza-like illness, pain, discomfort.
Infections and infestations: Candidiasis, herpes simplex.
Investigations: Increased AST or blood pressure.
Metabolism and nutrition disorders: Decreased appetite, dehydration.
Musculoskeletal and connective tissue disorders: Muscle spasms, back pain, muscular weakness, myalgia, neck pain.
Nervous system disorders: Dizziness, headache, hypoaesthesia, migraine, sinus headache, paraesthesia, somnolence.
Psychiatric disorders: Insomnia, depression, abnormal dreams, nervousness.
Renal and urinary disorders: Blood in urine, glycosuria, pollakiuria, polyuria, proteinuria, UTI.
Reproductive system and breast disorders: Polymenorrhoea.
Respiratory, thoracic and mediastinal disorders: Cough, dyspnoea, dry throat, nasal congestion, oropharyngeal pain, rhinorrhoea, pleural effusion, nasopharyngitis, pharyngitis, URTI.
Skin and subcutaneous tissue disorders: Rash, hyperhidrosis, sunburn.
Vascular disorders: Hot flush.
Potentially Fatal: Severe cutaneous adverse reactions (e.g. Stevens-Johnson syndrome, toxic epidermal necrolysis).

Perform culture and susceptibility tests; consult local institutional recommendations before treatment initiation due to antibiotic resistance risks. Monitor for temperature, serum ammonia levels; blood in stool. Assess for skin reactions and changes in symptoms.

Increased systemic exposure with P-glycoprotein inhibitor (e.g. ciclosporin). May decrease or increase INR with warfarin.

Description:
Overview: Rifaximin is a nonabsorbed, broad-spectrum rifamycin derivative antibiotic. It has been shown to be active against aerobic bacteria, gram-negative bacteria and Escherichia coli (enterotoxigenic and enteroaggregative strains).
Mechanism of Action: Rifaximin binds irreversibly to the β sub-unit of the bacterial enzyme DNA-dependent RNA polymerase, resulting in the inhibition of bacterial RNA synthesis.
Pharmacodynamics: The main mechanism of resistance to rifaximin is mainly caused by mutations in the rpoB gene. This results in changes in the binding site on the DNA dependent RNA polymerase and reduces the binding affinity of rifaximin, thereby decreasing its efficacy.
Pharmacokinetics:
Absorption: Bioavailability: <0.4%. Time to peak plasma concentration: Approx 1 hour.
Distribution: Plasma protein binding: 67.5%.
Metabolism: Extensively metabolised in the liver mainly by CYP3A4.
Excretion: Via faeces (96.6%, mainly as unchanged drug); urine (0.32%). Elimination half-life: 5.6 hours.

Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 6436173, Rifaximin. https://pubchem.ncbi.nlm.nih.gov/compound/Rifaximin. Accessed Oct. 29, 2025.

Store between 20-25°C.

Other Antibiotics

A07AA11 - rifaximin ; Belongs to the class of antibiotics. Used in the treatment of intestinal infections.

Brayfield A, Cadart C (eds). Rifaximin. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 17/09/2025.

CARSL Consulting. Xifaxan 550 mg Film-coated Tablets data sheet May 2024. Medsafe. http://www.medsafe.govt.nz. Accessed 17/09/2025.

Joint Formulary Committee. Rifaximin. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 17/09/2025.

Normicron 200 mg Film-coated Tablets (Alfasigma S.p.A.). MHRA. https://products.mhra.gov.uk. Accessed 17/09/2025.

Normix (Alfasigma S.p.A.). MIMS Philippines. http://www.mims.com/philippines. Accessed 19/09/2025.

Rifaximin 550 mg Film-coated Tablets (Norgine Pharmaceuticals Limited). MHRA. https://products.mhra.gov.uk. Accessed 17/09/2025.

Rifaximin. UpToDate Lexidrug, AHFS DI (Adult and Pediatric) Online. American Society of Health-System Pharmacists, Inc. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 17/09/2025.

Rifaximin. UpToDate Lexidrug, Lexi-Drugs Multinational Online. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 17/09/2025.

Xifaxan Tablet (Salix Pharmaceuticals, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 17/09/2025.

Xifaxanta 200 mg Film-coated Tablets (Norgine Pharmaceuticals Limited). MHRA. https://products.mhra.gov.uk. Accessed 17/09/2025.