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Rifaximin Combined with Probiotics for Functional Diarrhea: A Prospective Cohort Study

This prospective cohort study suggests that combining rifaximin with probiotics may offer superior long-term improvements in stool consistency and frequency for adults with functional diarrhea compared to probiotics alone, though these exploratory findings warrant confirmation through randomized controlled trials.

Original authors: Jing Zhou, Guo-jian Yin, Yu-xin Liu, Feng-jie Ji

Published 2026-07-12

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Jing Zhou, Guo-jian Yin, Yu-xin Liu, Feng-jie Ji

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine your gut is a bustling city. Sometimes, for no clear reason, the traffic gets chaotic, and the "waste disposal" system starts spitting out loose, watery messes instead of solid, organized piles. This is called Functional Diarrhea. It's like a city where the roads are fine, but the traffic lights are just acting up, causing a constant flood of loose traffic.

For a long time, doctors have tried to fix this traffic jam with probiotics. Think of probiotics as friendly traffic officers sent in to calm the crowd and organize the flow. They help, but sometimes the traffic still gets a bit messy again once the officers leave.

Enter Rifaximin. This isn't a traffic officer; it's more like a specialized cleanup crew that sweeps the streets without ever leaving the city limits (it doesn't get absorbed into the rest of the body). The big question was: What happens if you send in the cleanup crew alongside the traffic officers? Does the city stay organized longer?

The Experiment: A Real-World Choice

Researchers in Suzhou, China, set up a study to find out. They didn't force patients into groups; instead, they let the patients choose their own path after a chat with their doctor.

Group A (The Combo): 62 people chose to take the probiotics plus the Rifaximin cleanup crew.
Group B (The Solo): 59 people chose to take just the probiotics.

They watched what happened at the end of the treatment and again one month later.

The Results: Who Kept the City Tidy?

Here is what the data showed, without the fancy medical jargon:

Both Groups Got Better: Whether they had the cleanup crew or just the officers, everyone's poop got more solid. The "loose traffic" turned into "solid piles" for almost everyone.
The One-Month Test: This is where things got interesting.
- The group with just probiotics started to slip back a little. Their poop consistency drifted back toward being a bit looser after a month.
- The group with Rifaximin plus probiotics held their ground. Their poop stayed solid and organized for longer.
- The Numbers: The study found that at the one-month mark, the combo group was significantly better at keeping things solid. The odds of their poop staying messy were much lower (specifically, the odds ratio was 0.399, with a 95% confidence interval of 0.165–0.964).
How Often They Went: Both groups went to the bathroom less often after treatment. But at the one-month mark, the Combo group was still going significantly less often than the Solo group. The difference was about 0.568 fewer bowel movements per day (95% CI -1.036 to -0.101).
The "Urgency" and "Incomplete" Feelings: Both groups felt less like they had to run to the bathroom in a panic, and both felt like they finished their business more completely. However, the study did not find a clear difference between the two groups here. The cleanup crew didn't seem to offer a special boost for these specific feelings compared to the officers alone.

What the Paper Doesn't Say (The Rules of the Game)

It is very important to know what this study didn't prove:

It's not a "Magic Bullet" yet: The authors are careful to say these are "exploratory findings." They are like a strong hint, not a final verdict.
No "Why" Yet: The study didn't look inside the gut to see how the bacteria changed. They are guessing that the cleanup crew helped the traffic officers work better, but they didn't actually take a photo of the microscopic city to prove it.
Not a Randomized Trial: Because patients chose their treatment, there might be other reasons why the Combo group did better (maybe they were more motivated to follow instructions). The study adjusted for this, but it's not as perfect as a coin-flip experiment.
Safety: No one got seriously hurt. The cleanup crew was safe, but the study didn't track every tiny, minor scratch or headache, so we can't say exactly how the "minor" side effects compared.

The Bottom Line

The study suggests that adding a short course of Rifaximin (taken as 400 mg twice daily for 6 consecutive days) to a standard probiotic routine might help people with Functional Diarrhea keep their stools solid for longer and go to the bathroom less often one month after treatment compared to probiotics alone.

However, the authors are quick to remind us: This is a suggestion, not a solved mystery. They explicitly state that these findings need to be confirmed in a randomized controlled trial (where patients are assigned by chance, not choice) before we can say for sure that the cleanup crew is the secret to a perfectly organized gut city. Until then, it's a very promising lead, but not the final answer.

Technical Summary: Rifaximin Combined with Probiotics for Functional Diarrhea

Problem Statement
Functional diarrhea (FDr) is a chronic gut-brain interaction disorder affecting approximately 5.6% of the population in China, characterized by loose or watery stools. While probiotics are commonly used to regulate gut microbiota, their efficacy as monotherapy is often inconsistent. Rifaximin, a non-absorbable broad-spectrum antibiotic, has shown promise in microbiota-related disorders like diarrhea-predominant irritable bowel syndrome (IBS-D), but conclusive evidence regarding its specific utility in FDr remains scarce. There is a need to evaluate whether combining rifaximin with probiotic therapy offers superior clinical outcomes compared to probiotics alone for this specific population.

Methodology
The study was a single-center, non-randomized prospective cohort conducted at the Second Affiliated Hospital of Soochow University (China) between April 2022 and June 2024.

Participants: 133 adults (aged 18–65) diagnosed with FDr according to Rome IV criteria were enrolled. Patients were allocated to treatment groups based on preference after physician counseling rather than randomization.
Interventions:
- Rifaximin-plus-Probiotics (RP) Group: Received rifaximin (400 mg twice daily for 6 days) combined with Bacillus licheniformis (0.25g TID for 12 days) and Lactobacillus acidophilus (0.5g TID for 12 days).
- Probiotics-Only (PO) Group: Received the same probiotic regimen without rifaximin.
Endpoints:
- Primary: Stool consistency measured by the Bristol Stool Form Scale (BSFS) at baseline (T1), end of treatment (T2), and 1 month post-treatment (T3).
- Secondary: Mean daily bowel movements (Daily BMs), urgency of defecation, and incomplete evacuation.
- Exploratory: Presence of flatulence, borborygmi, mucus, and frothy stool.
Statistical Analysis: Data were analyzed using adjusted ordinal repeated-measures models for stool consistency and generalized estimating equations (GEE) or repeated-measures linear models for other outcomes. Models were adjusted for sex and disease duration. Pairwise comparisons were corrected using the Bonferroni method.

Key Results
Among 121 patients who completed follow-up (62 in RP, 59 in PO), both groups showed significant improvement in stool consistency and symptom reduction over time.

Stool Consistency: While the overall group-by-time interaction was not significant ( $P=0.080$ ), the 1-month (T3) group-by-time estimate favored the RP group ($OR=0.399$, 95% CI 0.165–0.964, $P=0.041$ ). Descriptively, the median BSFS score in the RP group improved from 6 to 4 at T2 and remained at 4 at T3, whereas the PO group's score improved to 5 at T2 but regressed to 6 at T3.
Daily Bowel Movements: Both groups experienced a significant reduction in Daily BMs. The overall group-by-time interaction was significant ( $P=0.009$ ). At T3, the RP group demonstrated a statistically significant lower frequency of bowel movements compared to the PO group (mean difference = -0.568, 95% CI -1.036 to -0.101; adjusted $P=0.005$ ).
Other Symptoms: Urgency and incomplete evacuation improved significantly in both groups over time, but no statistically significant between-group differences were observed at any time point.
Exploratory Outcomes: The RP group showed a significantly lower risk of frequent flatulence at T3 compared to the PO group ( $P=0.046$ ). No clear between-group differences were found for borborygmi, mucus, or frothy stool.
Safety: No serious adverse events were reported. Both regimens were well-tolerated.

Significance and Claims
The authors conclude that the combination of rifaximin and probiotics is associated with better maintenance of stool consistency improvement and lower stool frequency at one month post-treatment compared to probiotics alone. They posit that while probiotics provide a foundational therapy, the addition of rifaximin may offer a short-term maintenance benefit for FDr symptoms.

However, the paper maintains a modest tone regarding these claims. The authors explicitly state that:

The findings are exploratory and require confirmation in randomized controlled trials (RCTs).
The study design (non-randomized, patient preference-based allocation) introduces potential selection bias and residual confounding.
The observed benefits are primarily evident at the 1-month follow-up rather than immediately at treatment completion, suggesting a role in short-term maintenance rather than immediate relief.
The specific rifaximin regimen used (400 mg BID for 6 days) was based on local clinical practice and affordability, not a standard registration protocol for FDr, and thus does not establish an optimized dosing strategy.

The study highlights the potential of combining antimicrobial and probiotic strategies for FDr but emphasizes that the current evidence is insufficient to definitively claim superiority over probiotics alone without further rigorous investigation.

The Experiment: A Real-World Choice

The Results: Who Kept the City Tidy?

What the Paper Doesn't Say (The Rules of the Game)

The Bottom Line

Technical Summary: Rifaximin Combined with Probiotics for Functional Diarrhea

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