Rifaximax, a brand name for the antibiotic rifaximin, is prescribed for gastrointestinal conditions such as traveler's diarrhea caused by E. coli, and irritable bowel syndrome with diarrhea (IBS-D). Due to its low systemic absorption, most of its action is localized in the gut, which contributes to its generally favorable safety profile. Despite this, patients should be aware of the potential side effects, which can vary depending on the condition being treated and the duration of therapy.
Common side effects
Most side effects of Rifaximax 400 mg are mild and often resolve as the body adjusts to the medication. Many of the common gastrointestinal side effects can be difficult to distinguish from the symptoms of the condition being treated, such as diarrhea.
Gastrointestinal Issues
- Nausea: A frequently reported side effect, especially in patients with IBS-D.
- Stomach pain or bloating: Discomfort in the abdomen is common.
- Gas (flatulence): An increase in gas is possible.
- Constipation: While used to treat diarrhea, some patients may experience constipation.
- Headache: Reported by some patients, particularly during treatment for traveler's diarrhea.
Neurological and Systemic Effects
- Dizziness: Can occur in some individuals.
- Fatigue: A general feeling of tiredness has been reported.
Other Common Effects
- Peripheral edema: Swelling in the hands, feet, or ankles, although less frequent with the 400 mg dosage than the higher 550 mg used for hepatic encephalopathy.
- Joint pain: Some patients report mild joint discomfort.
Serious or less common side effects
While rare, some side effects can be more serious and require immediate medical attention.
Clostridioides difficile-associated diarrhea (CDAD) Like almost all antibiotics, rifaximin can disrupt the normal balance of gut bacteria, potentially allowing an overgrowth of C. difficile. This can lead to severe diarrhea, stomach cramps, and fever, sometimes occurring even after treatment is finished.
Severe allergic reactions In rare cases, a patient may experience a severe allergic reaction (anaphylaxis). Symptoms include:
- Skin rash, hives, or itching.
- Swelling of the face, throat, or tongue.
- Difficulty breathing or swallowing.
Other rare but serious effects
- Severe skin reactions: Such as Stevens-Johnson syndrome and toxic epidermal necrolysis, have been reported.
- Anemia: A decrease in red blood cell count, leading to paleness or shortness of breath.
- Abnormal liver enzyme levels: Some patients, particularly those treated for IBS-D, may show transient increases in liver enzymes.
Side effects based on condition treated
The frequency of certain side effects can differ depending on the condition being treated, as shown in the table below, which compares common adverse events reported in clinical trials.
| Side Effect | Traveler's Diarrhea (TD) | IBS-D (550 mg) | Hepatic Encephalopathy (HE) (550 mg) |
|---|---|---|---|
| Headache | Very Common (>10%) | Common (≥2%) | Common (≥5%) |
| Nausea | Common (≥2%) | Common (≥2%) | Very Common (≥10%) |
| Dizziness | Not commonly reported | Common (≥2%) | Very Common (≥10%) |
| Fatigue | Not commonly reported | Common (≥2%) | Very Common (≥10%) |
| Peripheral Edema | Not commonly reported | Not commonly reported | Very Common (≥10%) |
Managing and monitoring side effects
While most side effects are mild, it is important to communicate with a healthcare provider throughout treatment.
For mild symptoms:
- Hydration: Stay well-hydrated, especially if experiencing diarrhea, to help with dizziness and fatigue.
- Timing: Taking the medication with food can help reduce nausea.
- Rest: For fatigue, ensure adequate rest.
When to contact a healthcare provider:
- If mild side effects are bothersome or persist beyond a few days.
- If you experience signs of a serious allergic reaction, such as a severe rash, hives, or swelling of the face and throat.
- If you develop severe or bloody diarrhea, especially if accompanied by fever, during or up to two months after finishing the medication.
Important Considerations
- Pre-existing conditions: Inform your doctor of any pre-existing conditions, especially liver disease or a history of C. difficile infection.
- Dehydration: Monitor for signs of dehydration, such as dry mouth or decreased urination.
Conclusion Overall, Rifaximax (rifaximin) has a favorable safety profile for most patients due to its minimal absorption into the body. The side effects are typically mild and often manageable with simple measures. However, the potential for rare but serious side effects, such as C. difficile infection and severe allergic reactions, highlights the importance of open communication with a healthcare professional. Patients should be aware of the specific side effects associated with their treated condition and seek medical advice if any symptoms become severe or concerning. For more detailed prescribing information and drug details, you can consult the RxList entry for Xifaxan.
