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Linzess Vs Miralax: Discover the Best Option for Your Tummy

Linzess Vs Miralax

Linzess Vs Miralax is a comparison of the two drugs used to treat constipation. Miralax is a time-tested medicine and has been in use since 1999.

Linzess on the other hand has been approved in 2012, however, it is still not commonly used.

One reason for the less utilization of Linzess Vs Miralax is that Linzess is a prescription medicine while Miralax is available OTC.

Some Basic Similarities and Differences Between Linzess and Miralax:

Linzess (Linaclotide) is a relatively new medication. It activates the guanylate cyclase receptors present in the small intestinal lumen.

Activating these receptors results in the secretion of bicarbonate-rich fluid into the intestinal lumen. Thus, it softens the stools by adding more water to it.

In addition, Linzess improves visceral pain associated with intestinal spasms and enhances intestinal motility.

Miralax (Polyethylene Glycol), on the other hand, is one of the safest osmotic laxatives.

Unlike lactulose, another commonly used osmotic laxative, it is not fermented by the gut bacteria and has little effect on the gut flora.

By acting as an osmotic laxative, it draws in water and softens the stools relieving constipation.

Here is a table of comparison of the common differences between Linzess and Miralax:




MedicineLInaclotidepolyethylene glycol 3350
Classguanylate cyclase-C agonistsOsmotic laxative
FormulationOral capsules: 72, 145, and 290 mcgPowder: 17 gm per packet
  • IBS-C: 290 mcg per day
  • CIC: 145 mcg per day
17 gm per day
IndicationsIBS-C and CICOccasional constipation
Onset of actionRapid onsetSlow onset
Duration of action1 day to 1 week1 day
OTC availablePrescription-onlyYes

Linzess is more effective, however, it is available only via a prescription while Miralax is available as OTC medicine for occasional constipation.

Linzess is indicated for chronic constipation that has not improved with Miralax and that is persistent. Linzess is also indicated for treating IBS-C, a type of irritable bowel syndrome with predominant symptoms of constipation.

In addition, Linzess is very costly. The per month cost at different pharmacies is around $500 to USD 600.

Miralax on the other hand is a much cheaper alternative to Linzess. It has an estimated price of about 2.25 USD per packet (USD 22.5 per 10 packets).



Linzess Vs Miralax for Constipation Relief:

The two drugs have not been evaluated in a head-to-head comparison trial. However, Miralax is safe with a gentle laxative effect indicated for the treatment of occasional constipation.

On the other hand, Linzess is indicated for chronic constipation, especially in those cases where no relief from constipation has been achieved with OTC laxatives like Miralax or other commonly used laxatives.

Linzess acts via mechanisms different than Miralax. It may also relieve abdominal pain and anxiety associated with chronic constipation and IBS.

Here is a table of comparison of Linzess vs Miralax for Constipation Relief:

Relieves Constipation✔✔
Increase gut motility
Relieves abdominal pain?
Relieves anxiety

In addition, Linzess is fast-acting. It relieves constipation within 1 to 3 days of taking it. Miralax is a gentle and slow-onset medicine. It may take 3 to 5 days to relieve constipation.

Miralax is a non-degradable laxative and hence, unlike other osmotic laxatives such as lactulose, it does not alter the gut bacteria.

The efficacies of Linzess vs Miralax compared to placebo medications have been outstanding. The results of a few independent clinical trials show improvement in 50% or more of the participants compared to placebo.




Relieves ConstipationIBS-C: 18 – 49%

CIC: 15 – 20%


  • 50 -57% over 6 – 12 months
Relieves abdominal pain34 – 50%Not studied

The table above is not a direct comparison. In addition, the indications, population, and circumstances were different. 

It is just an indirect observation of how effective are Linzess vs Miralax for relieving constipation and abdominal pain.

Linzess relieved constipation and abdominal pain within a few days while the final assessment of the efficacy was based on self-assessment reports after 6 to 12 months.

Furthermore, Linzess use was associated with clinically significant improvement in abdominal pain while Miralax had no such effect.



In conclusion: Which is Better Miralax or Linzess?

Miralax and Linzess are both effective drugs for relieving constipation. However, Linzess has a more rapid onset of action, is probably more effective, and relieves abdominal pain and anxiety in addition to constipation.

Miralax on the other hand is a very cheap medicine, available over the counter and does not need a prescription, and is used to treat occasional constipation.

It has not been studied particularly in patients with IBS. However, since it does not alter the gut flora and is considered more safe and effective than lactulose.

What do you think?

Written by Dr. Ahmed

I am Dr. Ahmed (MBBS; FCPS Medicine), an Internist and a practicing physician. I am in the medical field for over fifteen years working in one of the busiest hospitals and writing medical posts for over 5 years.

I love my family, my profession, my blog, nature, hiking, and simple life. Read more about me, my family, and my qualifications

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