Xifaxan vs. Lactulose

Authored by The Rx Advocates, / Medically Reviewed by Dr. Conor Sheehy, PharmD, BCPS


These two drugs have common ground in that they are treatments for bowel issues. From there they take opposite courses. Xifaxan and Lactulose can also treat hepatic encephalopathy in advanced liver disease because they help reduce toxins from the bloodstream.

What Is Xifaxan?

Xifaxan is a tablet generally used to treat irritable bowel syndrome (IBS) and has been met with moderate success. The drug was patented in 2004 and Bausch Health is currently fighting in court to retain the rights to the drug. The patent is set to expire in 2029, but Norwich Pharmaceuticals is trying to gain early market access to its generic brand.

There are no generic forms of Xifaxan available at the current time.

The main application of Xifaxan is the treatment of IBS. According to the main Xifaxan website, the drug is administered for two weeks followed by up to six months without symptoms.

Salix Pharmaceuticals, a subsidiary of Bausch Health, has published data indicating that 52% of patients felt pain relief, 76% reported less diarrhea, and 47% felt relief in both areas. A placebo was administered and all three areas reported lower levels than the actual drug.

It was also reported that 36% of patients had no symptoms after six months.

According to the literature, a Xifaxan regimen can safely be repeated twice.

Xifaxan is an antibiotic that helps reduce IBS by reducing the growth of harmful bacteria in the gut. It specifically targets the gut. The chemical compound avoids absorption into the bloodstream and remains to attack bacteria in the specific area.

As an alternate use, doctors have been researching using Xifaxan to treat both hepatic encephalopathy in patients with cirrhosis of the liver. According to the research, Xifaxan has ‘beneficial effects’ by ‘affecting the gut-liver axis’ in a manner that helps the body filter harmful toxins that a patient with liver cirrhosis can not manage on their own.

What Is Lactulose?

Lactulose is generally used to treat constipation. It is also commonly prescribed to treat hepatic encephalopathy, a liver problem resulting in a buildup of toxins in the system and depressed cognitive function.

The drug is a synthetic sugar and is administered in a liquid form either orally or as an enema.

There is no exclusive patent on Lactulose and multiple brands are available, including Kristalose, Generlac, Enulose, and Constulose. These generic brands help keep the cost down.

When used to promote liver function it can offer clearer thinking as it helps cleanse toxins from the bloodstream. People report having improved brain function within hours of administering the solution in enema form and within a day or so when taken orally.

Lactulose has varying dosages that depend on the purpose of the prescription.

When taken for constipation, the dosage will generally be a single dose every day until normal bowel movements have resumed.

If the purpose of the prescription is to treat hepatic encephalopathy, the dosage is increased to three times daily orally or 4-6 times in enema form.


 Xifaxan is to treat diarrhea and Lactulose helps treat constipation.

Their overlap lies in the alternate treatment of liver disease. Both drugs have a positive impact on treating hepatic encephalopathy and providing improved cognitive function as a result. More studies are being done that point to Xifaxan having a greater impact on improved liver function than just dealing with hepatic encephalopathy.

Even in this area, they are not competitors. Lactulose functions by specifically helping the liver filter ammonia from the blood and purging it from the body.

Xifaxan affords a more broad-spectrum approach. Promoting good gut health, allows the liver to filter out more toxins that would build up due to cirrhosis and other liver impairing diseases.

While neither of these drugs is a cure for liver ailments, when used in conjunction with other drugs, they have proven to be very effective in relieving symptoms of liver disease.

According to the research, there is still a large portion of gut health doctors who still do not fully understand. Because of the impact on overall gut health Xifaxan has by targeting harmful bacteria in the intestines, it is believed that it holds an edge over Lactulose in liver health.

Both drugs require a prescription from your doctor.

Consult your physician and depending on your symptoms, you may find that one of these two drugs can be the right fit for you. It may be the case that your doctor prescribes both of them to enhance your liver function.



As with many drugs, Xifaxan has a long list of side effects. According to records from the trials, less than 15% of patients suffered minor side effects and only about 0.4% suffered side effects that caused them to stop taking the drug.

The Mayo Clinic lists side effects that should be brought to a doctor’s attention such as:

  • Black, tarry stool
  • Muscle spasm
  • Dizziness or lightheadedness
  • Trouble sleeping
  • Rapid breathing
  • Shortness of breath
  • Chest pain
  • Blood in the urine
  • Bloody nose
  • A feeling of constant movement of self or surroundings
  • Continuing ringing or buzzing or other unexplained noise in the ears
  • Fainting
  • Sunken eyes
  • Increased heart rate
  • Sensation of spinning
  • Unusual tiredness or weakness
  • Ulcers, sores, or white spots in the mouth
  • Unusual bleeding or bruising

Side-effects that do not require a doctor’s visit are:

  • Bloated
  • Difficulty with moving
  • Excess air or gas in the stomach or intestines
  • Full feeling
  • Fever
  • Frequent urge to defecate
  • Muscle pain or stiffness
  • Headache
  • Lower back or side pain
  • Passing gas
  • Pain in the joints
  • Swelling of the hands, ankles, feet, or lower legs
  • Stomach pain
  • Straining while passing stool
  • Chills
  • Abnormal dreams
  • Blurred vision
  • Decreased urination
  • Confusion
  • Cough
  • Dry lips
  • Difficulty having a bowel movement (stool)
  • Dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • Feeling of warmth
  • Dry mouth
  • Ear pain
  • Lightheadedness
  • Hearing loss
  • Nausea
  • Loss of appetite
  • Loss of taste
  • Pale skin
  • Painful or difficult urination
  • Sweating
  • Redness of the face, neck, arms, and occasionally, upper chest
  • Sore throat
  • Wrinkled skin
  • Swollen glands
  • Thirst
  • Vomiting

Side effects should not be taken lightly. While the Mayo Clinic lists these as less problematic, it is always a good idea to monitor side effects and consult a doctor if they last more than a couple of days without any improvement.


The list of side effects for Lactulose is shorter than for Xifaxan.

The most common side effect is diarrhea. After that, the list is:

  • Bloating
  • Gas
  • Nausea
  • Vomiting
  • Cramps

There are reports of severe muscle cramping and irregular heartbeat. If either of these symptoms appears, contact your physician immediately.

As mentioned above, if any of the mild side effects last for more than a couple of days you should contact your doctor to make sure it is not a sign of a larger problem or a problem with dosage.

What Can The Rx Advocates Do For You?

The Rx Advocates work hard to make prescription drugs more affordable. Whether working through discount coupons or patient assistance programs, The Rx Advocates provides solutions to medication costs.

Lactulose is a common solution for constipation and sometimes hepatic encephalopathy. The Rx Advocates does not provide any support for this medication as it is available in generic form and is affordable. It is readily available for under $30 a bottle.

Xifaxan is on the other end of the spectrum. It retails for over $2000 per bottle.

Due to the legal battle over the Xifaxan patent, there is only one source of medicine. This prohibits people from finding an affordable option for purchasing their needed medication.

At The Rx Advocates, we work as the middle-man to work for individual patients to connect them with the best options for making their medications more affordable. Whether that is finding the right coupons, the right grant program, or the best patient assistance programs, we are dedicated to helping people.

Our research on Xifaxan is a great starting place if your doctor has prescribed this medicine.

You will be able to find information on coupons, alternatives, and background information to educate yourself about the drug you are taking.

Contact Us today and see how we can help you fill your prescriptions without draining your wallet.

  1. Xifaxan. Xifaxan (rifaximin 550 mg tablets). 2022. Available at xifaxin.com.
  2. Endpoints News. Bausch Health asserts push to ‘vigorously’ defend Xifaxan patent litigation. August 1, 2022. Available at endpts.com.
  3. AASLD. The Use of Rifaximin in Patients With Cirrhosis. January 2021. Available at aasldpubs.onlinelibrary.wiley.com.
  4. MedlinePlus. Lactulose. June 2017. Available at medlineplus.gov.
  5. Cleveland Clinic. Hepatic Encephalopathy. April 2020. Available at my.clevelandclinic.org.
  6. Mayo Clinic. Rifaximin (Oral Route) Side Effects. February 2021. Available at mayoclinic.org.
  7. DailyMed. Xifaxan – rifaximin tablet. October 2020. Available at dailymed.nlm.nih.gov.
  8. National Health Services. Side effects of lactulose. March 2022. Available at nhs.uk.
  9. National Library of Medicine. Rifaximin. June 14, 2018. Available at NCBI.nlm.nih.gov.
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