Best Drugs for Constipation

Expensive prescription drugs are rarely the answer. Simple over-the-counter options like Miralax, Ex-Lax, or Ducolax usually do the trick.

Close up of flusher handle on a toilet Photo: Kinga Krzeminska/Getty Images

Based on all the ads for prescription laxatives, you may think that the country is gripped by an epidemic of hard-to-treat constipation. And the Food and Drug Administration seems to think so, too. It has approved five new prescription medications for the problem in the past four years.

But while constipation can be serious and require medical intervention, in many cases lifestyle and diet changes suffice. And when they don’t, prescription drugs are usually not needed, says Arnold Wald, MD, a professor of gastroenterology and hepatology at the University of Wisconsin School of Medicine and Public Health.

More on Digestive Health

While all the new prescription products provide more treatment options, Wald says, most people don’t need them.

Instead, over-the-counter drugs such as polyethylene glycol (Miralax and generic), bisacodyl (Dulcolax laxative tablets and generic), or senna (Ex-Lax, Senokot, and generic) are a far better choice. They tend to work at least as well, often have more evidence for their safety, and are much cheaper.

For example, generic polyethylene glycol costs less than $15 for a month’s supply. Someone without health insurance would have to shell out $500 monthly or more for many of the prescription drugs.

Here’s what you need to know about treating constipation. 

What Counts as Constipation Anyway?

It’s a myth that a daily bowel movement is essential to good health, Wald says. But having fewer than three bowel movements per week, excessive straining, a sense of not being finished, or having hard, lumpy stools are signals you may have constipation.

About 15 percent of Americans suffer from the condition for months and even years, studies show. Women are three times as likely as men to experience constipation, and seniors are also at high risk. 

“Occasional constipation is quite common,” says Brian Lacy, MD, a gastroenterologist at the Mayo Clinic in Jacksonville, Fla., and co-editor in chief of The American Journal of Gastroenterology. “Many patients note a change in their usual bowel habits when they change their daily routine, travel, change their diet (especially if they go on a weight-loss program), or reduce their level of activity.” 

But for some people the condition becomes chronic, with uncomfortable symptoms lasting three months or longer.

Fiber First

Whether you’ve been constipated for days or months, the first steps should be to adjust your diet and habits

“Many of us don’t eat a very high-fiber diet,” Wald points out. Dietary fiber from foods such as vegetables, fruits, whole grains, and nuts helps create softer, bulkier stools that pass through your gut more quickly. 

If you can’t get enough fiber in your diet, consider a supplement. Those containing psyllium, such as Metamucil, Konsyl, and generics, may work better than other forms, research suggests. 

Wald also recommends getting more physical activity, which can help get the bowels moving.

OTC Laxatives

When boosting fiber and exercise doesn’t do the trick, it’s reasonable to consider an over-the-counter laxative. 

In general, OTC laxatives work by increasing water content in the stool so that it’s softer and easier to pass, Wald says. All of them are safe and effective for most patients. But you may find that one type works better for you or causes fewer side effects. “Everyone’s colon is a little different,” he says. 

Occasional constipation usually lasts only a few days and will resolve on its own, Lacy says. If you’re really uncomfortable, you can take an OTC laxative until things get back to normal.

For chronic constipation that has gone on for months, Lacy advises giving a drug time to work. “If someone does not improve after four weeks, then I recommend switching to another agent,” he says. In some cases, your doctor may recommend combining different types of medications.

Here’s a summary of the types of laxatives you’ll find on your drugstore shelves:

Polyethylene glycol (MiraLax and generic) works by pulling water into the colon, which softens the stool and stimulates the walls of the intestine to move it along. Its safety and effectiveness make it a first choice for many doctors and patients.

A recent analysis of 41 studies of OTC laxatives published in The American Journal of Gastroenterology found robust evidence that polyethylene glycol works well for chronic constipation while causing minimal side effects. The analysis found that it worked better than prescription laxatives. Lacy recommends taking it after dinner so that it kicks in after your breakfast the next morning. It can take a couple of days before you notice a difference in your bowel movements. 

Stimulant laxatives such as bisacodyl (Dulcolax laxative tablets and generic) and senna (Ex-Lax, Senokot, and generic) trigger rhythmic contractions in the intestinal muscles that push stools through more quickly. That action stimulates sluggish bowels and keeps stools soft as the colon has less time to absorb the moisture. The recent review of OTC drugs found good evidence to recommend senna for chronic constipation and moderate evidence for bisacodyl.

The downside to stimulant laxatives, according to the review, is that they can cause side effects such as abdominal pain and diarrhea. “Because they stimulate the colon, sometimes they can cause spasms or cramps,” Lacy says. “That said, they are effective.” The products generally start to work within 6 to 12 hours. 

Magnesium-based laxatives contain compounds that draw water into the stool, such as magnesium hydroxide (Phillips’ Milk of Magnesia and generic) and magnesium citrate (Citroma and generic.) The American Journal of Gastroenterology review found moderate evidence to support the use of magnesium laxatives for chronic constipation. 

Senna and magnesium-based laxatives were equally effective, according to a randomized clinical trial of 90 people with chronic constipation published in January 2021 in The American Journal of Gastroenterology. Those taking senna were more likely than people taking a magnesium laxative to reduce their dose because of side effects. 

The kidneys help process magnesium. So people with kidney disease should avoid anything other than the occasional use of magnesium-based laxatives to prevent a buildup of dangerously high levels of the mineral in the body.

Stool softeners such as docusate sodium (Colace, Phillips’ Stool Softener, and generic) and docusate calcium alter the surface of the stool, allowing in more water and oil. By making stools easier to pass, these drugs can help in certain situations—after surgery, for example, when you want to avoid straining to have a bowel movement. But research shows that stool softeners aren’t effective for chronic constipation.

Suppository laxatives such as Fleet Glycerin Suppository and Dulcolax Medicated Laxative Suppository usually take effect in less than an hour. They can be helpful for occasional constipation but aren’t intended for everyday use, Wald says.

Prescription-Drug Options for Constipation

If you’re still backed up a week after being on OTC laxatives, talk with your healthcare provider, Lacy says. Your doctor may be able to determine an underlying cause for your symptoms. For example, medical conditions such as diabetes or an underactive thyroid can cause constipation, as can many common medications, including certain antacids, antidepressants, antihistamines, blood pressure drugs, pain relievers, and drugs for urinary incontinence. 

Your doctor can also advise you on doses and timing of OTC products to get better results. If none of those approaches work, it’s time to consider a prescription solution. But don’t expect a miracle.

Prescription drugs to treat constipation are relative newcomers to the market. Since 2017 the FDA has approved plecanatide (Trulance), tenapanor (Ibsrela), prucalopride (Motegrity), and lactitol (Pizensy) as well as naldemedine (Symproic) for opioid-induced constipation. 

In addition, prescription drugs cost much more than their OTC counterparts. Without insurance, they cost about $450 to $550 a month, according to GoodRx. And with the exception of some older osmotic laxatives, none of those drugs are available yet as a low-cost generic. So even with insurance, you may be on the hook for a sizable co-pay.

For all those reasons, most people should consider prescription drugs only after OTC remedies haven’t worked. “You don’t go on to those drugs until you’ve failed at what’s cheap and readily available,” Wald says.

Here’s a summary of prescription medications that the FDA has approved for treating chronic constipation: 

Secretory laxatives including linaclotide (Linzess), lubiprostone (Amitiza), and plecanatide (Trulance) work by causing the intestines to secrete more fluid and may also help block abdominal pain. All the drugs in this category are also FDA-approved for treating irritable bowel syndrome with constipation. 

“The worst side effect for all three [available] agents is diarrhea,” Lacy says. About 5 percent of people taking Linzess experience severe diarrhea, research suggests, compared with about 1 to 2 percent with the other drugs in this class. Amitiza is more likely than the other drugs to cause nausea. Nearly 30 percent of people taking the recommended dose of the drug reported feeling nauseous compared with only 3 percent in the placebo group. Taking the drug with food can reduce that side effect, Lacy says. 

Prucalopride (Motegrity) stimulates muscles in the G.I. tract to move things along. Common side effects include abdominal pain, diarrhea, headache, and nausea. Most people experiencing diarrhea or headache reported that the symptoms got better in a few days. In addition, Motegrity carries a warning that it could cause suicidal thoughts or behavior, although the FDA has not conclusively linked the drug to that risk.

Osmotic laxatives such as lactulose (Constulose, Enulose, and generic) work similarly to OTC polyethylene glycol and aren’t necessarily any better than the cheaper drugstore product Wald says.

Few studies have compared constipation medications head-to-head. To get an idea of relative effectiveness, researchers from the U.S. and the U.K. analyzed data from 33 studies comparing a drug with a placebo. Results published online in August 2019 in The Lancet Gastroenterology & Hepatology found that after four weeks, the OTC stimulant laxatives bisacodyl and sodium picosulfate ranked first in effectiveness but last in terms of side effects; after 12 weeks, Motegrity came out on top. 

The choice for which prescription drug to take often comes down to what’s covered under a patient’s health insurance, Lacy says. Due to the warning, some insurers won’t cover prucalopride unless a patient hasn’t responded to one of the secretory laxatives.

Drugs for Constipation From Opioids

Opioid pain relievers such as Vicodin, Percocet, and Oxycontin are known not only for their risk of addiction but also for constipation. Forty to 80 percent of people taking opioids for long-term pain experience constipation, according to the American Gastroenterological Association.

The FDA has approved three drugs specifically for constipation caused by taking prescription opioids for pain: methylnaltrexone (Relistor), naldemedine (Symproic), and naloxegol (Movantik).

These medications, called peripherally acting mu-opioid receptor antagonists or Pamoras, relieve constipation by preventing opioids from attaching to receptors in the intestines. The drugs contain a compound that keeps them from reaching the brain, so they don’t interfere with an opioid’s pain-relieving effects.

But patients with opioid-induced constipation should still try OTC laxatives before considering a prescription drug, according to AGA guidelines published in 2019. “You want to give routine laxatives a chance because many times you can treat the constipation without going to an opioid antagonist,” Wald says. 

As with other prescription constipation drugs, one big drawback of Pamoras is price. The average cash price for a month’s supply of Movantik is $442; Symproic, $474; Relistor tablets, $2,362; and injectable Relistor, a whopping $4,840, according to GoodRx.

If OTC laxatives don’t work, AGA guidelines strongly recommend naldemedine based on high-quality evidence and naloxegol based on moderate-quality evidence that the drug works.

Naldemedine is also the only drug of the three backed by long-term safety data (a year’s worth). The AGA gave methylnaltrexone a conditional recommendation based on a lack of good evidence supporting the drug. The group also noted that it costs far more than other drugs in its class. 

Amitiza is FDA-approved for treating opioid-induced constipation as well as chronic constipation. But the AGA didn’t find enough evidence to make a recommendation for using that or other types of prescription drugs (besides Pamoras) to treat constipation caused by opioids.

Teresa Carr

Teresa Carr is an award-winning journalist with a background in both science and writing, which makes her curious about how the world works and eager to tell you about it. She is a former Consumer Reports editor and 2018 Knight Science Journalism Fellow at MIT and has more than two decades' experience reporting on science, health, and consumer issues.