Rifaximin (Xifaxanta)

O que é Rifaximin?

Rifaximin (sold under the brand name Xifaxanta in the European Union) is a semi-synthetic, broad-spectrum antibiotic derived from Rifamycin SV. It is distinguished from conventional antibiotics by one critical pharmacological property: it is almost entirely non-absorbed. Less than 0.4% of an oral dose reaches the systemic circulation, meaning that Rifaximin acts almost exclusively within the gastrointestinal tract.

This unique property makes Rifaximin clinically valuable for intestinal conditions where gut-focused antibacterial activity is desirable without systemic antibiotic exposure. The Agência Europeia de Medicamentos (EMA) has approved Rifaximin for:

• Irritable Bowel Syndrome with Diarrhoea (IBS-D) in adults (as Xifaxanta 550 mg)
• Reduction of risk of overt hepatic encephalopathy recurrence in adults
• Traveller’s diarrhoea caused by non-invasive strains of Escherichia coli

Como funciona Rifaximin work?

Rifaximin inhibits bacterial DNA-dependent RNA polymerase, the enzyme responsible for transcribing bacterial DNA into RNA. By blocking this enzyme, Rifaximin prevents bacteria from synthesising the proteins they need to replicate and survive.

Because Rifaximin acts within the intestinal lumen rather than systemically, it selectively modifies the composition of the gut microbiome — the trillions of microorganisms that inhabit the intestinal tract. In IBS-D:

• Dysbiosis correction: Clinical evidence supports a role for gut bacterial dysbiosis and small intestinal bacterial overgrowth (SIBO) in a subset of IBS-D pacientes. By reducing populations of pathogenic or overgrown bacteria, Rifaximin may restore a healthier microbial balance.
• Reduced intestinal inflammation: Rifaximin appears to have anti-inflammatory properties mediated partly through pregnane X receptor (PXR) activation, independent of its direct antibacterial effects.
• Reduced gut permeability: Evidence suggests Rifaximin may help restore intestinal barrier integrity, reducing the “leaky gut” phenomenon associated with some forms of IBS.
• Symptom relief: Clinical trials in IBS-D have demonstrated statistically significant improvement in bloating, global IBS symptoms, and stool consistency compared to placebo.

Para quem é Rifaximin for?

Rifaximin is appropriate for adults with:

• IBS-D: Confirmed or clinically suspected irritable bowel syndrome with diarrhoea as the predominant symptom pattern, who have not achieved adequate relief with dietary measures, antispasmodics, or other first-line tratamentos
• Traveller’s diarrhoea: Uncomplicated diarrhoea acquired during travel to endemic regions, caused by non-invasive E. coli (Rifaximin is not appropriate for invasive pathogens causing dysentery or bloody diarrhoea)
• Hepatic encephalopathy: To reduce recurrence risk in pacientes with cirrhosis and a history of overt hepatic encephalopathy (typically under specialist supervision)

Rifaximin is not appropriate for:

• Diarrhoea complicated by fever or blood in the stool (invasive pathogens — requires systemic antibiotics)
• Children under 12 years (IBS-D indication)
• Patients with severe intestinal obstruction
• Patients with hypersensitivity to Rifaximin or other Rifamycin antibiotics
• Pregnant women (insufficient safety data)

Dosagem

For adults, EMA-approved dosing schedules are:

Indication	Dose	Duration
IBS-D	550 mg three times daily	14 days
Traveller’s diarrhoea	200 mg three times daily	3 days
Hepatic encephalopathy prevention	550 mg twice daily	Long-term (specialist supervision)

Tablets may be taken with or without food. For IBS-D, the 14-day course can be repeated if symptoms recur, under medical guidance.

Efeitos secundários

Rifaximin is generally well tolerated, in large part because of its minimal systemic absorption.

Efeitos secundários comuns

• Nausea: Mild and generally transient
• Flatulence (gas): Increased gas production, which may be related to shifts in gut bacterial populations
• Abdominal pain: May overlap with underlying IBS symptoms
• Headache
• Dizziness (uncommon)

Menos comuns efeito secundários

• Rectal tenesmus (sensation of incomplete emptying)
• Peripheral oedema (fluid retention — reported in hepatic encephalopathy pacientes at long-term doses)
• Skin rash

Serious but rare efeito secundários

• Clostridium difficile-associated diarrhoea (CDAD): As with all antibiotics, Rifaximin carries a theoretical risk of C. difficile overgrowth, though the risk is substantially lower than with systemically absorbed antibiotics due to its local intestinal action.
• Severe allergic reactions: Including anaphylaxis and serious skin reactions. Patients with known Rifamycin hypersensitivity are at higher risk (cross-reactivity possible).

Rifaximin vs alternativas for IBS-D

Medicine	Class	Mode of Action	Best For
Rifaximin (Xifaxanta)	Non-absorbed antibiotic	Gut microbiome modification	IBS-D, bloating, SIBO
Loperamide	Opioid receptor agonist	Slows intestinal motility	Acute diarrhoea management
Hyoscine Butylbromide	Antispasmodic	Smooth muscle relaxation	IBS cramping and pain
Low-FODMAP diet	Dietary intervention	Reduces fermentable substrate	First-line IBS management
Eluxadoline	Mixed opioid agonist/antagonist	Reduces bowel motility + pain	IBS-D (restricted use, specialist)

Como obter Rifaximin online na Europa

Rifaximin is a medicamento sujeito a receita médica in the EU. Prescrivia operates as a technology intermediary — we do not prescribe medicamentos, employ médicos, or sell medicamentos. Our platform connects pacientes with independent EU-registered médicos who can conduct online digestive health assessments.

The process:

1. Complete a digestive health assessment: Describe your IBS symptoms, predominant pattern (diarrhoea, constipation, mixed), symptom severity, and previous tratamentos.
2. Avaliação médica: An independent EU-registered médico reviews your assessment. If Rifaximin is clinically appropriate for IBS-D or another qualifying indication, they may issue a receita médica.
3. Receita e dispensa: If a receita médica is issued, it is forwarded to a licensed EU farmácia partner for dispensing and delivery.

Important: A Prescrivia não garante that a receita médica will be issued. All prescribing decisions are made independently by qualified medical professionals based on your individual clinical circumstances.

Informação de segurança importante

Do not take Rifaximin if you:

• Have diarrhoea accompanied by fever or blood in the stool (seek urgent medical attention — systemic infection is likely)
• Are hypersensitive to Rifaximin or other Rifamycin antibiotics
• Are pregnant or breastfeeding
• Have significant intestinal obstruction

Informe o seu médico if you:

• Are taking Ciclosporin (a significant drug interaction — Rifaximin exposure increases substantially)
• Are taking P-glycoprotein inhibitors (may increase systemic Rifaximin exposure)
• Have severe hepatic impairment (Rifaximin accumulation possible in hepatic encephalopathy pacientes with severe liver disease)
• Experience worsening diarrhoea or new symptoms during tratamento

Stop tratamento and seek medical advice if:

• Diarrhoea continues for more than 48 hours without improvement, or worsens
• You develop fever or see blood in your stool

Fontes

Medical information on this page is based on the following sources:

• Agência Europeia de Medicamentos (EMA). Xifaxanta (Rifaximin) — Summary of Product Characteristics and European Public Assessment Report. ema.europa.eu
• Pimentel M, et al. Rifaximin therapy for pacientes with irritable bowel syndrome without constipation (TARGET 1 and TARGET 2). N Engl J Med. 2011;364:22-32.
• Organização Mundial da Saúde (WHO). Diarrhoeal diseases. who.int
• Cremonini F, Lembo A. Rifaximin for the tratamento of irritable bowel syndrome. Expert Opin Pharmacother. 2012.

This content is provided for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for advice relevant to your individual health circumstances.