RIFAXIMIN Drug Interactions: What You Need to Know

INTERACTIONS Warfarin: Monitor INR and prothrombin time; dose adjustment of warfarin may be needed to maintain target INR range. ( 7.2 ) 7.1 P-glycoprotein Inhibitors Concomitant administration of cyclosporine, an inhibitor of P-gp and OATPs significantly increased the systemic exposure of rifaximin. In patients with hepatic impairment, a potential additive effect of reduced metabolism and concomitant P-gp inhibitors may further increase the systemic exposure to rifaximin. Caution should be exercised when concomitant use of XIFAXAN and a P-gp inhibitor such as cyclosporine is needed [see Warnings and Precautions ( 5.5 ), Clinical Pharmacology ( 12.3 )].

7.2 Warfarin Changes in INR have been reported postmarketing in patients receiving rifaximin and warfarin concomitantly. Monitor INR and prothrombin time. Dose adjustment of warfarin may be needed to maintain target INR range. See prescribing information for warfarin.

7.3 CYP3A4 Substrates An in vitro study has suggested that rifaximin induces CYP3A4 <span class="opacity-50 text-xs">[see Clinical Pharmacology ( 12.3 )]</span> . However, in patients with normal liver function, XIFAXAN 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.

XIFAXAN is contraindicated in patients with a hypersensitivity to rifaximin, any of the rifamycin antimicrobial agents, or any of the components in XIFAXAN. Hypersensitivity reactions have included exfoliative dermatitis, angioneurotic edema, and anaphylaxis [see Adverse Reactions ( 6.2 )] . History of hypersensitivity to rifaximin, rifamycin antimicrobial agents, or any of the components of XIFAXAN. ( 4) )

AND PRECAUTIONS

• Travelers’ Diarrhea Not Caused by E. coli : XIFAXAN was not effective in diarrhea complicated by fever and/or blood in the stool or diarrhea due to pathogens other than E. coli . If diarrhea symptoms get worse or persist for more than 24 to 48 hours, discontinue XIFAXAN and consider alternative antibiotics. ( 5.1 )
• Clostridium difficile -Associated Diarrhea: Evaluate if diarrhea occurs after therapy or does not improve or worsens during therapy. ( 5.2 )
• Hepatic Impairment: Use with caution in patients with severe (Child-Pugh Class C) hepatic impairment. ( 5.4 , 8.7 )
• Concomitant P-glycoprotein (P-gp) inhibitors (e.g., cyclosporine): Caution should be exercised when concomitant use of XIFAXAN and a P-glycoprotein inhibitor is needed. ( 5.5, 7.1 )

5.1 Travelers’ Diarrhea Not Caused by Escherichia coli XIFAXAN was not found to be effective in patients with diarrhea complicated by fever and/or blood in the stool or diarrhea due to pathogens other than Escherichia coli. Discontinue XIFAXAN if diarrhea symptoms get worse or persist more than 24 to 48 hours and alternative antibiotic therapy should be considered. XIFAXAN is not effective in cases of travelers’ diarrhea due to Campylobacter jejuni . The effectiveness of XIFAXAN in travelers’ diarrhea caused by Shigella spp. and Salmonella spp. has not been proven. XIFAXAN should not be used in patients where Campylobacter jejuni, Shigella spp., or Salmonella spp. may be suspected as causative pathogens [ see Indications and Usage ( 1.1 )].

5.2 Clostridium difficile- Associated Diarrhea Clostridium difficile- associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including XIFAXAN, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon which may lead to overgrowth of C. difficile. C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents. If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C . difficile, and surgical evaluation should be instituted as clinically indicated.

5.3 Development of Drug-Resistant Bacteria Prescribing XIFAXAN for travelers’ diarrhea in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.

5.4 Severe (Child-Pugh Class C)

Hepatic Impairment

There is increased systemic exposure in patients with severe hepatic impairment. The clinical trials were limited to patients with MELD scores <25. Therefore, caution should be exercised when administering XIFAXAN to patients with severe hepatic impairment (Child-Pugh Class C) [ see Use in Specific Populations ( 8.7 ), Clinical Studies ( 14.2 )].

5.5 Concomitant Use with P-glycoprotein Inhibitors Concomitant administration of drugs that are P-glycoprotein (P-gp) inhibitors with XIFAXAN can substantially increase the systemic exposure to rifaximin. Caution should be exercised when concomitant use of XIFAXAN and a P-gp inhibitor such as cyclosporine is needed. In patients with hepatic impairment, a potential additive effect of reduced metabolism and concomitant P-gp inhibitors may further increase the systemic exposure to rifaximin <span class="opacity-50 text-xs">[see Drug Interactions ( 7.1 ), Clinical Pharmacology ( 12.3 )]</span>.