Drug Interactions and What to Avoid While on Xifaxan
While Xifaxan (rifaximin) has minimal systemic absorption, making many typical drug interactions less likely, specific substances can significantly alter how the medication works or increase the risk of side effects. It is critical to discuss all medications, supplements, and herbal products with a healthcare provider before starting Xifaxan.
Interacting Medications
Several prescription medications have known interactions with Xifaxan, primarily those that inhibit a protein called P-glycoprotein (P-gp), which helps clear drugs from the body. When this protein is inhibited, the level of Xifaxan in the body can increase significantly, raising the risk of side effects.
- Cyclosporine: This immunosuppressant drug is a potent P-gp inhibitor. Co-administering cyclosporine with Xifaxan can dramatically increase systemic rifaximin levels, potentially leading to a higher risk of side effects.
- Warfarin: This blood thinner may have its effects altered by Xifaxan, though the exact mechanism is not fully understood. It could either decrease or increase the anticoagulant effect, leading to a risk of blood clots or bleeding, respectively. Close monitoring of INR (International Normalized Ratio) is necessary if these drugs are taken together.
- Certain Antifungals: Drugs such as ketoconazole and itraconazole can inhibit P-gp, potentially increasing the risk of Xifaxan side effects.
- Certain Antibiotics: Some macrolide antibiotics, including clarithromycin and erythromycin, can also increase the risk of Xifaxan side effects.
- HIV and Hepatitis C Medications: Some medications used to treat HIV (e.g., ritonavir) and hepatitis C (e.g., sofosbuvir/velpatasvir) can interact with Xifaxan and increase the risk of side effects.
- Antiarrhythmics and Calcium Channel Blockers: Certain heart medications like amiodarone, propafenone, and verapamil have been noted to interact.
Dietary and Lifestyle Precautions
While Xifaxan can be taken with or without food, and there are no known direct food interactions with the medication itself, certain dietary and lifestyle choices should be avoided or managed carefully based on the condition being treated and potential side effect exacerbation.
Alcohol and Grapefruit Juice
- Alcohol: Although no direct interaction is known, alcohol can worsen Xifaxan side effects like headache, nausea, and dizziness. For individuals with hepatic encephalopathy, alcohol can further impair liver function and trigger an episode. It can also exacerbate symptoms of IBS-D and traveler's diarrhea. It is generally advisable to limit or avoid alcohol during treatment.
- Grapefruit Juice: This is a major interaction to avoid. Grapefruit and its juice are potent P-gp inhibitors, which can drastically increase the body's exposure to Xifaxan, leading to a higher risk of adverse effects.
Cannabis and CBD
- Cannabis/CBD: Cannabis and CBD products have been reported to interact with Xifaxan. They can inhibit P-gp, causing an increase in rifaximin exposure and a higher risk of side effects, especially in patients with liver problems. Inform your doctor if you use cannabis before starting treatment.
Dietary Adjustments for Underlying Conditions
- SIBO/IBS-D: For conditions like Small Intestinal Bacterial Overgrowth (SIBO) and Irritable Bowel Syndrome with Diarrhea (IBS-D), dietary modifications are often recommended. A low-FODMAP diet, which limits fermentable carbohydrates, may be advised to manage symptoms and prevent recurrence, often implemented after the Xifaxan treatment is complete. Some specialists, however, recommend a regular diet during treatment to make bacteria more metabolically active and vulnerable to the antibiotic.
- Hepatic Encephalopathy: Patients being treated for hepatic encephalopathy may be advised to avoid high-salt foods.
Table: Comparison of Xifaxan with and without Interacting Substances
| Substance/Condition | With Xifaxan | Without Xifaxan | Clinical Implication |
|---|---|---|---|
| P-gp Inhibitors (e.g., Cyclosporine) | Increased Xifaxan side effect risk | Xifaxan levels normal | Close monitoring required or alternative therapy |
| Warfarin | Altered blood-thinning effect | Blood-thinning effect stable | Monitor INR closely, adjust warfarin dose |
| Alcohol | Worsened GI symptoms, amplified side effects (e.g., dizziness) | Standard GI symptoms, standard side effects | Advisable to limit or avoid alcohol |
| Grapefruit Juice | Drastically increased rifaximin exposure, high risk of side effects | Standard rifaximin levels | Avoid consumption entirely |
| Cannabis/CBD | Increased rifaximin levels and side effect risk | Standard rifaximin levels | Avoid during treatment, discuss with doctor |
| Severe Liver Disease | Higher blood levels of Xifaxan, increased side effect risk | Normal clearance of Xifaxan | Increased monitoring for side effects |
Important Precautions and Warnings
- Pre-existing Conditions: Inform your doctor if you have severe liver disease, bloody diarrhea, or diarrhea accompanied by a fever. Xifaxan is not intended for these more severe forms of diarrhea, and alternative treatment may be necessary.
- Full Course of Treatment: As with any antibiotic, it is essential to complete the full prescribed course of Xifaxan, even if symptoms improve. Stopping early can lead to a return of the infection and contribute to antibiotic resistance.
- Antibiotic-Associated Diarrhea (AAD): In rare cases, Xifaxan can lead to an overgrowth of Clostridioides difficile (C. diff), causing severe, watery, or bloody diarrhea. This can occur even months after stopping the medication. If you experience these symptoms, contact your healthcare provider immediately.
- Severe Allergic Reaction: Seek immediate medical help if you experience a rash, hives, facial swelling, or trouble breathing, as these could be signs of a serious allergic reaction.
- What Xifaxan Doesn't Treat: Xifaxan is an antibacterial, not an antiviral. It will not be effective against diarrhea or other illnesses caused by a virus, such as the common cold or flu.
- Do Not Crush Tablets: Xifaxan tablets should be swallowed whole. Crushing the tablets may affect how effectively the medication works.
Conclusion
Taking Xifaxan effectively involves more than just following the dosage. By being aware of and actively avoiding specific drug interactions, lifestyle factors like alcohol and cannabis use, and dietary considerations related to the underlying condition, patients can maximize the benefits of treatment while minimizing risks. Always maintain open communication with your healthcare provider and pharmacist about all other medications, supplements, and any persistent or new symptoms you experience. For more detailed prescribing information, consult the manufacturer's official resources or a trusted drug information database like Drugs.com.
