Dulcolax vs. Miralax: Differences, similarities, and which is better for you

Drug overview & main differences | Conditions treated | Insurance coverage and cost comparison | Side effects | Drug interactions | Warnings | Which is right for me? | FAQ

Dulcolax and Miralax are two popular, FDA-approved over-the-counter laxatives used to treat occasional constipation and irregularity. While both help relieve constipation, they are different types of laxatives—Dulcolax can provide fast relief, while Miralax takes longer to work. Continue reading to learn more about Dulcolax and Miralax. 

What are the main differences between Dulcolax and Miralax?

If you struggle with hard stools, stools that are difficult to pass, or have less than three bowel movements per week, you are likely experiencing constipation. Constipation is a very common problem in the United States, affecting 16 out of 100 adults, and 33 out of 100 adults aged 60 and older.

Dulcolax is a stimulant laxative that contains the active ingredient bisacodyl. It works by increasing the activity of the intestines to cause a bowel movement. Dulcolax, as a brand name, is also available in various other formulations that do not contain bisacodyl, such as liquid and soft chews (which contain magnesium) and a stool softener (which contains docusate sodium). For the purpose of this review, we will focus on the Dulcolax laxative, which contains bisacodyl. 

Miralax is an osmotic laxative containing the ingredient polyethylene glycol 3350. Miralax works by attracting water in the colon, softening stools, and making them easier to pass. 

Conditions treated by Dulcolax and Miralax

Dulcolax tablets and suppositories are used for the temporary relief of occasional constipation and irregularity. The tablets produce a bowel movement in 6 to 12 hours, and the suppositories work quicker, producing a bowel movement in 15-60 minutes.

Miralax is also indicated for the relief of occasional constipation and irregularity and produces a bowel movement in one to three days.

Dulcolax or Miralax are often used in bowel preparation for a procedure, such as a colonoscopy. Before you prepare for your procedure, your surgeon will give you instructions for use, as well as a list of foods and drinks you can consume on a clear liquid diet. 

Coverage and cost comparison of Dulcolax vs. Miralax

Because you can get them over-the-counter, Dulcolax and Miralax are usually not covered by insurance or Medicare Part D. Some exceptions may apply, for example, a state Medicaid plan. Also, you may be able to use your health savings credit card to pay for these OTC medications. 

The typical out-of-pocket price for a bottle of generic Dulcolax tablets is about $13, and a box of suppositories is also about $13. The out-of-pocket price for a bottle of generic Miralax is about $19.

You can save money on Dulcolax or Miralax with a SingleCare card. (Note—although both drugs are OTC, a prescription is needed to apply the SingleCare discount. Simply follow these steps here.) 

Common side effects of Dulcolax vs. Miralax

With either drug, rare but serious allergic reactions may occur. If you experience hives, trouble breathing, or swelling of the face, tongue, or throat, seek immediate medical attention.

Dulcolax side effects

Common side effects of Dulcolax include:

• Nausea
• Vomiting
• Diarrhea
• Stomach cramps
• Local rectal irritation (from the suppository form)

Serious side effects of Dulcolax may include

• Electrolyte imbalance (symptoms may include decreased urine, fatigue/weakness, irregular heartbeat, dizziness, fainting, or confusion)
• Loss of colon function (after taking Dulcolax for too long) 

Miralax side effects

Common side effects of Miralax include:

• Nausea
• Stomach cramping
• Gas

Serious side effects of Miralax may include:

• Excessive bowel movements/persistent diarrhea
• Severe stomach pain
• Bloody stools/rectal bleeding

Drug interactions of Dulcolax vs. Miralax

Dulcolax drug interactions 

Because the combination could increase the risk of stomach cramps and other side effects, Dulcolax should not be taken within one hour of antacids, such as:

• Gaviscon 
• Maalox
• Mylanta
• Phillips’ Milk of Magnesia
• Rolaids
• Tums

Dulcolax should not be taken within one hour of proton pump inhibitors, such as:

• Nexium
• Protonix

Because the combination could increase the risk of ulcers or colitis, Dulcolax should not be taken with other stimulant laxatives such as:

• Correctol
• Ex-Lax
• Glycerin suppositories
• Senna/Senokot

Miralax drug interactions

Miralax should not be taken with:

• Linzess (the combination can increase the risk of dehydration and electrolyte abnormalities) 
• Trintellix or Fetzima (the combination may increase the risk of SIADH or low sodium) 

This is not a full list of drug interactions. Other drug interactions may occur. Consult your healthcare provider for more information about drug interactions and how they may affect you. 

Warnings of Dulcolax and Miralax

It is always a good idea to consult with a healthcare provider of gastroenterology (gastroenterologist) for medical advice if you experience bowel problems, especially if you have frequent or chronic constipation. The gastroenterologist can do a full workup and evaluation to determine if you have any underlying conditions causing your constipation that need to be treated. Some things to consider with both drugs include:

• Consult your healthcare provider before using if you are pregnant or breastfeeding or have any medical conditions, such as irritable bowel syndrome (IBS) or liver or kidney disease. 
• Read the label on the package and ask your healthcare provider before using if you have any questions or concerns.
• Prolonged use of laxatives can lead to electrolyte imbalance or other complications. Consult your healthcare provider if your constipation continues for more than seven days or if you have any serious or concerning symptoms, such as severe pain or rectal bleeding.

Which is right for me?

When deciding which medication to try, you can consider a few factors. First, you will want to think about how fast you want to go to the bathroom. Are you very uncomfortable and want to go as quickly as possible? Or would you prefer more gentle, overnight relief? Considering this factor, Dulcolax tablets will work in about 6-12 hours, while the suppositories will work more quickly, within an hour. Miralax can take one to three days to produce a bowel movement. 

You’ll also want to consider the type of medication. Do you prefer a tablet, a powder mixed into a liquid, or a rectal suppository? Some individuals may not have a preference, but if you have a strong preference for the type of medication you can tolerate, that may factor in as well. 

It is always a good idea to discuss treatment options with your healthcare provider, who is most qualified to help you decide which treatment to try, taking into account your medical history and conditions, as well as any medications you take that could interact with Dulcolax or Miralax. 

Frequently asked questions about Dulcolax vs. Miralax

Are Dulcolax and Miralax the same?

Both medications are laxatives but they are different types of laxatives and work in different ways. Dulcolax works faster than Miralax. 

There are also other types of laxatives, compared in the chart below. 

Is Dulcolax or Miralax better?

The two drugs have not been compared in clinical trials. You may want to consider the type of medication you prefer (tablet, suppository, or powder mixed into a liquid) as well as how fast you would like to have a bowel movement. For example, if you’re uncomfortable and want to go to the bathroom fast and don’t mind inserting a rectal suppository, a Dulcolax suppository will have you in the bathroom within the hour. 

Can I use Dulcolax or Miralax while pregnant?

If you are pregnant or breastfeeding, consult your healthcare provider before using a laxative. 

Can I use Dulcolax or Miralax with alcohol?

Alcohol may worsen constipation. If you are experiencing constipation, you should avoid alcohol. Also, alcohol can worsen the side effects of laxatives, such as bloating, nausea, stomach pain, and dehydration.

What is the best fast-acting laxative?

A Fleet Saline Enema can produce a bowel movement as quickly as one to five minutes. A Dulcolax suppository can produce a bowel movement in 15-60 minutes. A saline laxative, such as magnesium citrate, can produce a bowel movement in a half hour to six hours. Depending on your preference (enema, suppository, or liquid) and your level of discomfort, you can choose one of these, and it should work very quickly.