Treating Mixed IBS (IBS-M): Options and Clinical Trials

Mixed irritable bowel syndrome (IBS-M) can be especially frustrating because it combines periods of diarrhea and constipation, often along with abdominal pain, bloating, and urgency. Many people spend years trying diets and medications without a clear plan, or without understanding why their symptoms swing so much from one week to the next.

In this article, we walk through the current approach to treating IBS-M and how gastrointestinal clinical trials are helping drive new options within gastroenterology research. If you know someone dealing with unpredictable digestive symptoms, feel free to share this — it might help them find a more structured path forward.

What Is Mixed IBS and How Is It Diagnosed?

IBS-M is a subtype of irritable bowel syndrome in which, over time, a person experiences both hard stools/constipation and loose stools/diarrhea. Diagnosis is based on clinical criteria — symptoms and bowel pattern — and on ruling out "red flags" that could point to another condition.

Warning signs that call for a broader medical workup include: unintentional weight loss, blood in the stool, anemia, fever, nighttime symptoms, onset later in life, or a family history of colorectal cancer or inflammatory bowel disease.

Guidelines from the American College of Gastroenterology (ACG) note that IBS is a symptom-based diagnosis, and that the approach should be individualized — avoiding unnecessary testing when there are no alarm features — while prioritizing evidence-based strategies.

Treating IBS-M: A "By-Symptom" Plan, Not a Single Pill

IBS-M treatment tends to work best when it targets your current predominant symptom — pain, bloating, diarrhea, or constipation — and adjusts dynamically, rather than relying on one medication for everything.

1) Diet and Habits: The Foundation

• Soluble fiber (like psyllium) can help, especially during constipation-predominant phases, without worsening bloating as much as some insoluble fibers.
• Identifying triggers: greasy meals, alcohol, carbonated drinks, excess caffeine.
• Sleep, activity, and bowel routine: often underestimated, but relevant.

A low-FODMAP diet can help some patients, ideally with professional guidance to avoid unnecessary restriction or nutrient gaps. The NIDDK outlines dietary and lifestyle options that may improve IBS symptoms, including individualized food adjustments.

2) Managing Pain and Bloating

In IBS-M, pain is usually tied to visceral hypersensitivity and spasm. Depending on the case, your gastroenterologist may consider:

• Antispasmodics
• Gut-brain axis modulators (for example, certain low-dose antidepressants)
• Targeted treatments for gas/bloating in select patients

3) When Diarrhea Predominates (IBS-D-type phases)

• Antidiarrheal agents as directed
• Specific therapies based on evaluation (never self-medicate if there's blood, fever, or severe pain)
• Temporary dietary adjustments, such as reducing irritants or managing lactose intake if relevant

4) When Constipation Predominates (IBS-C-type phases)

• Gradually increasing water and soluble fiber
• Osmotic laxatives in some cases
• Prescription medications for constipation/IBS-C in select patients

5) Evidence-Based Psychological Therapy (When Appropriate)

IBS-M can worsen with stress, anxiety, or major life events. Interventions like cognitive behavioral therapy or gut-directed hypnotherapy have shown benefit for certain patients and can be part of a comprehensive approach.

Why Can IBS-M Be Hard to Control?

1. Symptoms shift, and treatment isn't adjusted in time.
2. Only bowel habits are treated, while pain, stress, or sleep are overlooked.
3. There's a coexisting condition — food intolerances, bacterial overgrowth in some cases, pelvic floor disorders, among others — that needs a different strategy.

That's why a structured medical plan and close follow-up are key to avoiding directionless "trial and error." If your IBS symptoms haven't improved with standard management, it may also help to look at our Gastroenterology Services, covering IBD and IBS/GERD, at Gastro SB Clinic.

Advances and Opportunities Through Gastrointestinal Clinical Trials

Even with today's range of treatments, some patients with IBS-M still don't respond well enough. That's where gastrointestinal clinical trials matter: they let researchers evaluate new therapies for pain, motility, the microbiome, low-grade inflammation, and gut-brain axis modulators.

Gastroenterology clinical research also helps identify which patient subgroups — for example, those with more pain versus more bloating — benefit most from specific strategies. Participating in a clinical trial in San Diego may be an option for people who:

• Have moderate to severe symptoms despite standard treatment

(👉 Dr. Alayo: please fill in the rest of this list with the criteria you had in mind. In the meantime, I've closed the piece using the site's standard participation language.)

If you'd like to understand how trials work before deciding, start with What's a Clinical Trial? You may also be interested in our earlier post on IBS and gastrointestinal clinical trials.

How to Participate

Whether you're a potential candidate to join an IBS-M-related study as a patient, interested in participating as a "healthy volunteer" for the control group, or a healthcare professional interested in collaborating with our research team — just contact us. Our team can walk you through the eligibility process and answer your questions.

This article is for informational purposes only and is not a substitute for medical evaluation. Participation in any clinical trial is entirely voluntary and subject to an eligibility screening process; joining does not guarantee access to a specific treatment or any particular outcome. If you're experiencing warning signs such as bleeding, unintentional weight loss, or severe pain, we recommend scheduling an appointment as soon as possible.

Want to learn more about clinical trials for IBS and other digestive conditions? Call or text (619) 513-3372, or visit our Clinical Trials page.