rifaximin

Action and Spectrum

Actions and Spectrum: 

rifaximin is a broad-spectrum, non-absorbable antibiotic with the following actions and spectrum: 

• Mechanism of action: rifaximin inhibits bacterial RNA synthesis by binding to the beta subunit of bacterial DNA-dependent RNA polymerase, preventing transcription initiation. It ultimately leads to the death of the bacteria. 
• Non-systemic: rifaximin is not absorbed systemically in the gastrointestinal tract, which means it stays within the gut and does not enter the bloodstream. 
• Spectrum of activity: rifaximin has broad-spectrum activity against both Gram-positive and Gram-negative bacteria, including Escherichia coli, Salmonella species, Shigella species, Clostridium difficile, and other enteric pathogens. 
• Bactericidal activity: rifaximin is a bactericidal antibiotic that kills the bacteria directly rather than inhibiting their growth. 
• Limited resistance: rifaximin has a low propensity for developing resistance, as it targets a different site than most other antibiotics. 
• Anti-inflammatory effects: rifaximin has also been shown to have anti-inflammatory effects on the gut mucosa, which may contribute to its effectiveness in treating some gastrointestinal disorders. 
• Short-term treatment: rifaximin is typically used for short-term treatment of acute infectious diarrhea, traveler’s diarrhea, and hepatic encephalopathy. 

Drug Interaction

Adverse Reaction

Frequency defined 

>10% 

Flatulence 

1-10% 

Headache  

Rectal tenesmus  

Abdominal pain  

Defecation urgency  

Nausea  

Constipation  

Pyrexia  

Vomiting  

Frequency not defined 

Pruritus 

Rash 

Rhabdomyolysis 

Black Box Warning

There is no blackbox warning for this drug 

Contraindication / Caution

Contraindication/Caution: 

Contraindications: 

• Hypersensitivity: rifaximin should not be used in individuals with a history of hypersensitivity to rifampin, rifamycin, or any of the other ingredients in the formulation. 
• Clostridium difficile-associated diarrhea: rifaximin is contraindicated in patients with a known or suspected diagnosis of Clostridium difficile-associated diarrhea (CDAD). 
• Hepatic Impairment: rifaximin is contraindicated in patients with severe hepatic impairment (Child-Pugh Class C). 

Caution: 

• Renal Impairment: rifaximin should be used with caution in patients with renal impairment, as it is eliminated primarily through the kidneys. 
• Pregnancy and breastfeeding: The safety of rifaximin during pregnancy and breastfeeding has not been established, and therefore, it should be used with caution in pregnant and lactating women. 
• Interaction with drugs: rifaximin may interact with other medications such as anticoagulants, oral contraceptives, and immunosuppressants. Careful monitoring and dose adjustments may be necessary. 
• Gastrointestinal disorders: rifaximin may worsen symptoms of inflammatory bowel disease (IBD) and other gastrointestinal disorders. It should be used with caution in patients with a history of IBD or other gastrointestinal disorders. 

Pregnancy / Lactation

Pregnancy consideration:  

Pregnant females should consult the physician before taking medicine as the potential benefits should outweigh the potential risks. 

Breastfeeding warnings: Lactating females should not breastfeed during the medication. 

Pregnancy category: 

• Category A: Satisfactory and well-controlled studies show no risk to the fetus in the first or later trimester. 
• Category B: There is no affirmation of risk to the fetus found in animal reproduction studies, and there are not enough studies on pregnant women. 
• Category C: Adverse effects on the fetus found with evidence in animal reproduction studies and no adequate evidence for a product in humans; Pregnant women must take care of the potential risks. 
• Category D: There is adequate data available with sufficient evidence of human fetal risk from various platforms. However, despite potential dangers may be used only in emergency cases for potential benefits. 
• Category X: Drugs listed in this category outweigh risks over benefits. The drug is not for pregnant women. 
• Category N: No data is available for the drug under this category. 

Pharmacology

Pharmacology: 

rifaximin is a semi-synthetic, non-systemic antibiotic that works by inhibiting bacterial RNA synthesis. It is specifically designed to target gram-negative and gram-positive bacteria in the gastrointestinal tract without being absorbed into the bloodstream, which makes it useful for treating gastrointestinal infections. 

Pharmacodynamics: 

The pharmacodynamic parameters of rifaximin include minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time above MIC. MIC is the lowest concentration of the drug required to inhibit the growth of a bacterial population, while MBC is the lowest concentration required to kill the bacterial population. Time above MIC refers to the duration of time that the concentration of the drug in the body remains above the MIC for the bacterial population being targeted. 

Pharmacokinetics: 

Absorption 

Bioavailability is less than 0.4% 

Peak plasma time is achieved in 1 hour 

Distribution 

80-90% of the drug is distributed in gut  

Metabolism 

CYP3A4 metabolizes the drug in the hepatocytes in vitro 

Elimination and Excretion  

The half-life is 2-5 hours 

More than 90% of the drug is excreted in feces  

Adminstartion

Administration: 

• rifaximin is typically taken with or without food, as directed by the healthcare provider. 
• The tablets should be swallowed whole and should not be crushed or chewed. 
• The dosage of rifaximin may vary depending on the indication being treated. For example, the usual dose for travelers’ diarrhea caused by non-invasive strains of Escherichia coli is 200 mg three times daily for three days. 
• The duration of treatment may also vary depending on the indication being treated. For example, the treatment duration for hepatic encephalopathy may range from 6 months to 2 years. 
• It is important to complete the full course of rifaximin treatment as prescribed by the healthcare provider, even if symptoms improve before the end of treatment. 
• If a dose of rifaximin is missed, it should be taken as soon as possible. However, if it is almost time for the next dose, the missed dose should be skipped, and the regular dosing schedule should be resumed. 
• rifaximin should be stored at room temperature, away from heat and moisture. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: rifaximin 

Pronounced: ri-faks-i-min 

Why do we use rifaximin? 

rifaximin is an antibiotic medication used to treat various bacterial infections in the gastrointestinal tract, including: 

• Traveler’s diarrhea: rifaximin is effective in treating diarrhea caused by non-invasive strains of Escherichia coli, a common cause of traveler’s diarrhea. 
• Hepatic encephalopathy: rifaximin is used in the prevention of the recurrence of hepatic encephalopathy, a condition that occurs when the liver is unable to remove toxins from the blood, leading to neurological symptoms such as confusion, poor coordination, and coma. 
• Small intestinal bacterial overgrowth (SIBO): rifaximin is effective in the treatment of SIBO, which is an overgrowth of bacteria in the small intestine that can cause symptoms such as bloating, diarrhea, and abdominal pain. 
• Irritable bowel syndrome with diarrhea (IBS-D): rifaximin has been approved by the FDA for the treatment of IBS-D, a type of irritable bowel syndrome characterized by diarrhea.