Miralax vs. Senna for Constipation: 5 Differences to Consider

Constipation is a common issue that affects people of all ages. Most of the time, adding certain foods or drinks to your diet is enough to provide relief. But if lifestyle changes aren’t enough, an over-the-counter (OTC) laxative may help. Two popular choices are Miralax (polyethylene glycol 3350) and senna (Senokot, Ex-Lax).

These two laxatives are considered safe and effective for constipation. But when it comes to Miralax versus senna, which is the best choice? Here, we’ll review five differences between them to help you find the right fit for your needs.

1. Miralax and senna work differently to treat constipation

Miralax and senna are both treatments for constipation. But they work differently in your body.

Miralax is an osmotic laxative. It works by pulling more water into your stool. This extra water makes your stool softer and larger, which makes it easier to pass through your intestines. Miralax works better if you’re hydrated, so be sure to drink plenty of water while you’re taking it.

Senna, on the other hand, is a stimulant laxative. It works by making the muscles in your intestines more active. This helps move stool through your system.

2. Miralax and senna come in different dosage forms

Miralax and senna are available in different dosage forms. This can make a difference as far as convenience or your personal preference.

Miralax only comes as a powder. It must be mixed with 4 oz to 8 oz of liquid before you drink it. Miralax comes in single-use packets or a multiple-dose container. You can mix it with any type of beverage at any temperature.

Senna comes in several different dosage forms, including:

• Oral tablets (regular and extra strength)

• Chewable chocolate

• Gummies

• Oral syrup (liquid)

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You may also see supplements that contain senna in an herbal tea or powder. Keep in mind that these products often contain other ingredients along with senna. So check with your healthcare team before using them.

As you can see, senna comes in a wider variety of products. Tablets or chewable dosage forms may be a simpler option than Miralax powder if you’re on the go. But not all senna products contain the same amount of the active ingredient. So you’ll need to pay close attention to the recommended dosage to be sure you’re taking the right amount.

3. Senna typically works faster for constipation than Miralax

Senna tends to work faster than Miralax to relieve constipation. In most cases, you should have a bowel movement about 6 to 12 hours after you take it.

Miralax typically takes about 1 to 3 days to start working. So it may not be the best option if you’re looking for fast relief. But keep in mind that fast-acting laxatives tend to have more side effects to consider — more on that next.

4. Miralax may be a gentler option than senna

Miralax takes a bit longer to work for constipation. But it also tends to be a gentler laxative than stimulants such as senna. Side effects include nausea and bloating. But these side effects are typically mild, and they’re also less common with Miralax than with other laxatives. 

Since it stimulates the muscles in your gut, senna is more likely to cause stomach cramps and diarrhea. It may also cause more urgent bathroom trips than Miralax. So it’s a good idea to weigh how fast they work with the possible side effects when deciding between these two laxative options.

5. Miralax is approved for long-term use

You shouldn’t take an OTC laxative for more than 7 days without a healthcare professional’s OK. But if you need a long-term daily laxative, Miralax is a first-choice option. That’s because several clinical studies have shown it to be safe and effective for chronic constipation.

Senna hasn’t been well studied for chronic constipation. But we do know that long-term use and taking higher doses can lead to liver problems. So in most cases, senna is only recommended for occasional use for up to 1 week at a time.

Keep in mind that chronic constipation usually has an underlying cause. It could be related to other medications you take. Or there could be something more serious going on. So it isn’t something you should try to treat on your own. A healthcare professional can help determine the cause as well as the best way to address it.

Can you take Miralax and senna at the same time?

You shouldn’t take Miralax and senna at the same time unless your prescriber recommends it. In most cases, this combination is only used in preparation for a colonoscopy or other bowel-related procedure. 

Taking more than one laxative at the same time raises the risk of side effects. If one type of laxative isn’t effective, you can try a different one. Just be sure you’ve waited long enough for the first laxative to start working. 

If you’re unable to pass stool even after taking a laxative or you develop severe stomach pain, rectal bleeding, or a fever, seek emergency care. There could be a blockage in your bowel that requires immediate care.

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Written by:

Jill Barat, PharmD

Jill Barat, PharmD has 10 years of experience as a pharmacist, including as the pharmacist in charge at an independent sterile and non-sterile compounding pharmacy. She was also head of medical content for a telemedicine company.

Edited by:

Stacia Woodcock, PharmD

Stacia Woodcock, PharmD, is a pharmacy editor for GoodRx. She earned her Doctor of Pharmacy degree from the University of Kentucky and is licensed in New York and Massachusetts.

Reviewed by:

Ferras Bashqoy, PharmD, BCCCP, BCPPS

Ferras Bashqoy, PharmD, BCCCP, BCPPS, is a clinical pharmacotherapy specialist in the Neonatal Intensive Care Unit at Hassenfeld Children’s Hospital in NYC. He enjoys working with preterm newborns, as they are small but mighty.

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