Constipation From Your Medications: What’s the Best Laxative?

Stool can come in different shapes, colors, and textures depending on your diet and overall health. In general, the goal is for your stool to be soft in nature. For example, your stool consistency should be similar to toothpaste or soft-serve ice cream. But if you’ve ever had constipation or hard stools, you know that it can be an uncomfortable experience. Diet, dehydration, and poor exercise habits are common causes of constipation. But what happens when a medication you’re taking is to blame? This can happen with several medications, and opioid pain medications are often the culprit. 

Fortunately, you have a few options when medication makes you constipated. Simple lifestyle modifications like making changes to your diet, daily habits, or exercise routines can be a good place to start. If those changes aren’t enough to resolve your constipation, over-the-counter (OTC) laxatives may be your next best step. To ease your medication-induced constipation, here are the best medications to treat constipation. Learn how these medications can work together. 

How do medications cause constipation?

There are two main ways that medications cause you to be constipated. One way is by slowing the movement of stool through your colon (large intestine). The other is by causing your body to absorb more water from the colon. Both of these make the stool harder, drier, and slower to pass. Common classes of medication that cause constipation include:

• Opioid pain medications such as hydrocodone or oxycodone

• Anticholinergic medications including antihistamines and incontinence medications

• Weight loss medications like Ozempic, Wegovy, and Monjuro

Treating medication-induced constipation

Prevention is better than a cure. If you’re taking medications that cause constipation, the best thing to do is to try to optimize your bowel health. Here are some simple lifestyle changes that can prevent, reduce, and sometimes resolve medication-induced constipation: 

• Drink enough water every day to help keep your stool soft. This allows for easier movement of your stool through the colon.

• Eat a high-fiber diet with plenty of fruits, vegetables, and whole grains.

• Simulate digestion with regular exercise.

• Empty your bowels when you have the urge. Holding it in can make it harder to go later on.

• Use a footstool (or squatty potty) to improve your toileting posture. This will improve your mechanics for an easier bowel movement.

• Be consistent with the timing of your bowel movements. Your bowels work best when you have a consistent routine.

What to take for constipation

There are many types of OTC laxatives. Some can be taken by mouth (pills or powder) and others can be placed in the rectum (suppositories or enemas). These laxatives can work in different ways to help get things moving again. In general, suppositories and enemas work faster than medications taken by mouth. 

You can safely combine different types of laxatives for a greater effect. Typically, it’s best to start slowly. Try one laxative, and then increase the dose or add an additional medication over time until you get relief. If you do not get initial relief, see your healthcare professional for more guidance. 

Stimulant laxatives

Stimulant laxatives work by stimulating the muscles of your large intestines. Stimulated muscles move stool more quickly through your intestines and into your rectum for evacuation. This medication also lessens the amount of water your body absorbs from the intestines so your stool stays softer. For most people, a bowel movement occurs within 6 to 12 hours of taking a stimulant laxative. Examples of stimulant laxatives include:

• Senna (Senokot, Ex-Lax)

• Bisacodyl (Dulcolax), which comes as a pill or suppository

Osmotic laxatives

Osmotic laxatives work by bringing more fluid into the intestines to ease constipation. Depending on the product, it can take anywhere from 15 minutes to a few days for a bowel movement to occur.

Osmotic laxatives are available as liquids, suppositories, and powders that you mix into a beverage. 

Examples of osmotic laxatives include:

• Polyethylene glycol or PEG (Miralax, Glycolax)

• Magnesium citrate (Citroma)

• Magnesium hydroxide (Milk of Magnesia)

• Sorbitol

• Glycerin

• Saline enema (Fleet Enema)

These are all effective at treating medication-induced constipation. Glycerin suppositories work the fastest. Certain oral laxatives like PEG can take a few days. But if you’re concerned about side effects, PEG works well and causes less feelings of “urgency” and cramping compared to other options. If you have kidney problems, check with your healthcare professional before using an osmotic laxative.

Emollient laxatives or stool softeners

Emollient laxatives (stool softeners) help make stool softer and easier to pass by allowing water and fat to build up in it. They typically start working within 12 to 72 hours. The most common emollient laxative is docusate sodium (Colace, DocQLace). 

Emollient laxatives are not the best choice for medication-induced constipation. While they cause fewer side effects, they’re less effective than stimulant and osmotic laxatives. If you have a new opioid prescription, your prescriber may recommend taking one of these laxatives along with another type. This is to help prevent constipation from starting in the first place. In fact, you can find senna and docusate together in one pill as Senna-S or Dok Plus.

Which laxative works the fastest?

Now that you know what your options are, let’s talk about how to get things moving quickly. As mentioned above, suppositories and enemas typically work the fastest. But what about medications taken by mouth? Here’s a brief comparison of some of the popular medications. 

Senokot vs. Dulcolax

Senokot and Dulcolax are both stimulant laxatives. And they both work within 6 to 12 hours when taken orally. Dulcolax suppositories work faster, usually within 15 to 60 minutes.

Dulcolax can cause cramping, stomach pain, and diarrhea. This can also happen with Senokot, but it may be better tolerated.

Dulcolax vs. Miralax

As mentioned above, Dulcolax can take anywhere from 15 minutes to 12 hours to take effect, depending on how you take it. But it also has some unpleasant side effects.

Miralax, an osmotic laxative, typically takes 1 to 3 days to work. It’s only available as a powder that you mix into a beverage. Compared to Dulcolax, Miralax can take longer to work. But it is much more tolerated and tends to cause fewer side effects than other laxatives.

Colace vs. Miralax

Colace is a stool softener. So, it does not actually stimulate you to have a bowel movement. But it can help alleviate straining that comes along with constipation. 

Compared to Colace, Miralax may be a preferred choice. That’s because it softens stool and raises pressure in the colon to encourage bowel movements.

What prescription laxatives work for medication constipation?

What happens if OTC laxatives aren’t doing the trick? In this case, your healthcare professional may recommend a prescription medication. There are a few different options, especially for constipation caused by opioids.

Prescription options

There are some prescription laxatives your prescriber may try for chronic constipation if OTC laxatives aren’t working. These include:

• Lactulose

• Prucalopride (Motegrity)

• Linaclotide (Linzess)

• Plecanatide (Trulance)

With the exception of lactulose, these medications are only available as brand-name products. But manufacturer copay savings cards can help make your prescription more affordable.

Prescription laxatives for opioid-induced constipation

For opioid-induced constipation, there are specific prescription medications that block opioid effects in your gut. They work by targeting the cause of the problem. Options include:

• Naldemedine (Symproic)

• Naloxegol (Movantik)

• Methylnaltrexone (Relistor)

• Lubiprostone (Amitiza) 

With the exception of lubiprostone, these medications are only available as brand-name products. But if you have commercial insurance, you may be able to pay as little as $0 with a copay savings card from the manufacturer. Patient assistance programs may also be available.

What laxatives don’t work as well for medication constipation?

Experts recommend that a fiber-rich diet is important to overall health. But using fiber and laxatives — like Metamucil and Psyllium — won’t work well for medication constipation. These bulk-forming laxatives don’t work as stimulants. They are better used to treat constipation not caused by medications. That’s because they add bulk to the stool without helping it move, which can make the medication-induced constipation worse.

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Written by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Edited by:

Karla Robinson, MD

Karla Robinson, MD, is a medical editor for GoodRx. She is a licensed, board-certified family physician with almost 20 years of experience in health through varied clinical, administrative, and educational roles.

Reviewed by:

Valerie Emuakhagbon, MD

Valerie Emuakhagbon, MD, is a board-certified colorectal surgeon. A native of Dallas, Texas, she completed the six-year BA/MD program at the University of Missouri-Kansas City.

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