What Laxative Should I Take For Constipation?

Fiber Supplements (Bulk Laxatives)

Fiber supplements soften the stool and stimulate a bowel movement.

There are three basic types, each of which uses a different ingredient, such as psyllium, calcium polycarbophil, or methylcellulose.

Here's a quick overview of them:

• Psyllium breaks down in the gut and becomes a food source for good gut bacteria. It's used for various conditions, including IBS and diverticulosis (note that it's not recommended for diverticulitis). There is one significant side effect: Psyllium can cause intestinal gas. 
• Calcium polycarbophil absorbs water in the digestive tract, making stools softer and bulkier. One drawback: It needs to be spaced with other medications you're taking to ensure they're adequately absorbed. 
• Methylcellulose, like polycarbophil, is plant-based and absorbs water in the gut. It's much less likely to cause intestinal gas than other fiber laxatives.

As with all laxatives, drinking plenty of fluids while using fiber supplements is essential, or they can worsen constipation.

Three commonly used bulk laxatives include:

• Citrucel (methylcellulose)
• Metamucil (psyllium)
• FiberCon (calcium polycarbophil)

Fiber supplements can interact with other medications and reduce or delay their effectiveness. Antidepressants, diabetes medications, and carbamazepine are some of the medications that interact with fiber supplements. Always consult with your healthcare provider to ensure that your medications are safe to take with a fiber supplement.

Osmotic Laxatives

Osmotic laxatives work by increasing the amount of fluid secreted within the intestines, resulting in softer and easier-to-pass stools.

The three major osmotic laxatives are Miralax, lactulose, and milk of magnesia.

• MiraLax, the brand name for polyethylene glycol PEG, acts similarly to fiber laxatives, as it draws water into the stool, making it softer and easier to pass. It also stimulates more frequent bowel movements. Miralax has been found to cause less gas and bloating than other osmotic laxatives. 
• Lactulose increases the speed of intestinal contractions, stimulating bowel movements. 
• Milk of magnesia is no longer widely recommended because of the potential complications it may cause for patients with heart or kidney disease. There are safer and more effective options available.

Besides the popular brand MiraLax, common brand names of osmotic laxatives include

• Generlac (lactulose)
• Phillips' Milk of Magnesia (magnesium hydroxide)

Since osmotic laxatives draw water to the stool, overusing these medications may cause dehydration and electrolyte imbalances. Talk with your healthcare provider to ensure these laxatives are suitable for you.

Stimulant Laxatives

Stimulant laxatives work by triggering contractions in the bowels to move stool through, thus inducing a bowel movement.

A stimulant laxative is generally recommended as a short-term treatment for constipation. There is research suggesting that long-term use of these laxatives may be harmful to the colon and increase the risk of cancer.

Well-known product examples of stimulant laxatives include:

• Dulcolax and Carter's Little Pills (bisacodyl)
• Senokot (senna)
• ExLax (sennosides)

Always check with your healthcare provider before using any of these products, as they can interact with other OTC and prescription medications, and may be unsafe for people with certain underlying conditions. 

Herbal Stimulant Laxatives

Herbal laxatives contain lanthanides, chemical compounds that stimulate the intestines, improving motility in the gut (in other words, keeping things moving along more quickly).

Many different herbs and plants have a reputation for having laxative effects, such as:

• Aloe (a cactus-like plant)
• Cascara sagrada (a North American shrub)
• Frangula (alder buckthorn)
• Rhubarb (a perennial vegetable)

Herbal stimulant laxatives are not recommended for long-term use and can cause adverse gastrointestinal (GI) effects and other unpredictable reactions. Always consult a healthcare provider before using herbal remedies. 

Milk of Magnesia vs. MiraLax: What to Know

Both MiraLax and milk of magnesia are used as laxatives and work by softening stool. However, they have different compositions.

MiraLax (a hyperosmotic laxative), increases water in the intestines so stools can exit more rapidly. The active ingredient in MiraLax is polyethylene glycol (PEG) 3350. It is an FDA-approved OTC short-term treatment of occasional constipation in those 17 and older.

MiraLax comes as a powder for reconstitution (add the medication to four to eight ounces of a liquid and allow it to dissolve). A single dose is 17 grams (g), which generally produces a bowel movement in one to three days. It can be taken once per day and for no more than seven days.

PEG 3350 is also available under various brand names, such as:

• GaviLax
• HealthyLax
• SmoothLax

Milk of magnesia (a saline laxative) uses sodium to draw water into the intestines to help stools pass through more easily. The active ingredient in milk of magnesia is magnesium hydroxide.

This medication is used for other purposes (e.g., heartburn, upset stomach). When used as a laxative for occasional constipation, the daily dose is as follows:

• For adults and children aged 12 and older, the recommended quantity ranges between 30 mL (2 tablespoons) and 60 mL (4 tablespoons).
• For children aged 6 to 11, the suggested dose varies from 15 mL (1 tablespoon) to 30 mL (2 tablespoons).
• For children under age 6, consulting with a healthcare provider is recommended.

These dosages may be taken once a day, in divided doses, or as directed by your healthcare provider. Used as a laxative, milk of magnesia should produce a bowel movement within 30 minutes to six hours.

Do not use milk of magnesia for longer than seven days without medical supervision. Milk of magnesia should be shaken well before use and can be taken with a glass of water.

Brand names of this medication include:

• Phillips' Milk of Magnesia
• Pedia-Lax Chewable Tablets
• Dulcolax Milk of Magnesia
• Ex-Lax Milk of Magnesia 

Stool Softeners

Stool softeners do just what the name suggests: soften stool so it's easier to pass. They perform some of the same functions as laxatives but technically aren't laxatives because they don't stimulate the gut.

However, some people find stool softeners to be helpful for constipation and, because they are generally well-tolerated, they are a safe option to try.

At times, a stool softener may be a better option than a laxative to ease the completion of a bowel movement—for example, if you have hemorrhoids and/or are pregnant. You should consult your healthcare provider to determine the best way to help you move things forward.

Most stool softeners contain a medication called docusate. Brand names include:

• Colace
• Dulcolax Stool Softener
• Kao-Tin 

Stool softeners are recommended for short-term use, but you can use them longer if your healthcare provider gives you the green light.