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Laxatives

Written on May 24, 2018 by C. Fookes, BPharm

Medically reviewed on May 24, 2018 by C. Fookes, BPharm

What are Laxatives?

Laxatives are medicines that help resolve constipation or empty the bowel of fecal matter before procedures or surgery involving the lower bowel. There are several different types available (see differences below) and each type works in a particular way. Some soften or loosen up the stool, while others increase how frequently the large colon contracts which helps move the stool along the bowel.

Laxatives may also be called cathartics or purgatives.

What are laxatives used for?

Laxatives are used to:

Some laxatives may be used as a preventive measure in people prone to constipation to reduce the risk of constipation developing.  However, eating a healthy diet filled with fresh fruits, vegetables, and whole-grain products; regular exercise; and drinking at least eight cups of water a day can help prevent constipation in most people.

What are the differences between laxatives?

There are several different types of laxative, and each type differs in the way they work, their side effect profile, how long they take to start working, and how long they work for.

Some products may combine two different laxatives, such as a stimulant and a softening agent. These may not necessarily work any better than a single-use agent and may be more likely to cause side effects.

Bulking Agents (Fiber)

Fiber is found naturally in fruits and vegetables, nuts and whole-grain foods. Psyllium is a type of fiber that is commonly used as a bulking agent. Bulking agents absorb water and swell in the intestines to create a softer, bulky stool that is easy to pass.  This means that bulk laxatives need to be taken with plenty of water when they are used as a laxative otherwise they can make constipation worse or cause an intestinal obstruction.

Methylcellulose is another soluble fiber that is also a bulking agent. It may be less likely to produce gas than psyllium. Polycarbophil is also less likely to cause gas and bloating than psyllium but more likely to cause heartburn and cramping.

Bulking agents are usually recommended for normal or slow-transit constipation. They may also be used to treat bowel irregularity such as in irritable bowel syndrome and sometimes will help with diarrhea (in this instance they need to be taken with less water). They can also help lower cholesterol when taken with additional dietary measures. Many can be safely taken during pregnancy and breastfeeding when dietary changes fail to relieve constipation, although a doctor should be consulted first.

Generic name Brand name examples
methylcellulose Citrucel
polycarbophil Equalactin, Fiber Lax
psyllium Hydrocil, Konsyl, Laxmar, Metamucil

Chloride Channel Activators

These act on the intestinal tract membrane to increase fluid secretion and improve the passage of stools. They have minimal absorption beyond the intestine (this means they don't really get absorbed into the blood stream). They may be used to treat opioid-induced constipation or constipation unresponsive to other laxatives. They may also be used to treat irritable bowel syndrome that has constipation as its main symptom.

Generic name Brand name examples
lubriprostone Amitiza

Guanylate cyclase-C (GC-C) Agonists

GC-C agonists stimulate the secretion of chloride and bicarbonate into the intestine, which increases the amount of fluid in the bowel, loosening faecal matter and accelerating intestinal transit.

These are powerful laxatives which should only be used for constipation that has not responded to other measures. Their safety and effectiveness has not been established in children under the age of 18 and they should never be given to children aged less than six.

Generic name Brand name examples
linaclotide Linzess
plecanatide Trulance

Lubricants

Lubricant laxatives contain a type of oil that coats the fecal matter and lubricates the intestinal walls, allowing the stool to pass through the colon more easily. They are usually only given short-term for constipation.

Generic name Brand name examples
mineral oil Fleet mineral oil enema

Osmotic and Hyperosmotic Laxatives

Osmotic and hyperosmotic laxatives draw water into the bowel by a process called osmosis. Osmosis is when water moves from a less concentrated solution to a more concentrated solution, to balance out the concentrations. So osmotic and hyperosmotic laxatives are hypertonic, which means they have a higher salt concentration compared to normal bowel matter. It is important that sufficient water is drunk to enable the laxative to work effectively and also to prevent dehydration. Some (such as Prepopik) are only used for bowel cleansing prior to bowel procedures or rectal surgery.

Generic name Brand name examples
glycerin Fleet glycerin suppositories, Sani-Supp
lactulose Constulose, Kristalose
magnesium hydroxide Ex-Lax Milk of Magnesia, Phillip’s Milk of Magnesia
polyethylene glycol 3350 Clearlax, Glycolax
sodium biphosphate and sodium phosphate Fleet enema

sodium picosulfate, magnesium oxide, and citric acid

(also has a stimulant effect)

ClenpiqPrepopik
sodium sulphate/potassium sulfate/magnesium sulfate Suprep Bowel Prep Kit

Stimulant laxatives

Stimulant laxatives directly stimulate the lining of the intestine by directly acting on the tissues lining the bowel wall or the nerves within the bowel wall. This accelerates the speed at which the stool moves through the colon. Most work within a few hours. Long-term, regular use may cause laxative dependency

Generic name Brand name examples
bisacodyl Alophen, Dulcolax, Gen Lax
senna/sennosides Ex-Lax, Senokot, Senosol

sodium picosulfate, magnesium oxide, and citric acid

(also has an osmotic effect)

Clenpiq, Prepopik

Stool softeners

Stool softeners act like a surfactant and soften the stool allowing water to penetrate the stool easier.

Stool softeners may take a bit longer than other types of laxatives to start working but may be preferred by people who are recovering from surgery, just given birth, or with hemorrhoids.

Generic name Brand name examples
docusate Colace, Doculase

Are laxatives safe?

Laxatives provide a temporary way to increase the motility of the bowel or soften up faecal matter. However, if misused or overused, they can cause problems, such as chronic constipation

Laxatives should not be used in people with a suspected bowel obstruction or appendicitis. Overuse of laxatives and taking some laxatives, such as bulking agents without enough water can also increase the risk of a bowel obstruction. Intake of fiber-based laxatives should be gradually increased until the desired effect is achieved rather than large quantities taken initially.

Hyperosmotic laxatives may cause electrolyte disturbances and dehydration in some people; the elderly and those with renal impairment are most at risk.


Children under the age of six should not be given laxatives without a doctor’s recommendation. In addition, some laxatives, such as guanylate cyclase-C (GC-C) agonists and the chloride channel activators should be avoided in children. In clinical trials, the GC-C agonists caused severe diarrhea and dehydration which proved fatal for some juvenile mice.

Pregnant women should not use laxatives except on a doctor’s advice. In general, bulking agents and stool softeners are safe; however, stimulant laxatives may be harmful.

Long-term, regular use of stimulant laxatives may lead to laxative dependency and reduce the body’s natural ability to defecate.

What are the side effects of laxatives?

All laxatives have the potential to cause diarrhea, although other side effects vary depending on the type of laxative taken. Common side effects associated with each of the different type of laxative include:

  • Bulking agents: abdominal cramping, bloating, gas. May affect the absorption of some drugs (medications should be taken one hour before or two hours after consuming fiber-based laxatives)
  • Lubricants: When used for long periods of time, oil-based laxatives may prevent the absorption of fat-soluble vitamins from the intestine into the blood stream. They may also affect the absorption of some medications
  • Linaclotide: abdominal pain, severe diarrhea, heartburn, nausea
  • Lubriprostone: headache, nausea and severe diarrhea
  • Osmotic and hyperosmotic laxatives: Bloating, cramping, nausea, gas and increased thirst. The risk of dehydration and electrolyte disturbances with the stronger hyperosmotic laxatives is high particularly in older adults or those with renal impairment. Lactulose carries a high risk of flatulence (gas) because of the way it is broken by bacteria in the colon
  • Plecanatide: severe diarrhea, urinary changes, gas, pain, nausea
  • Stimulant laxatives: belching, cramping, and nausea. Senna may cause urine discoloration.

For a complete list of side effects, please refer to the individual drug monographs.

List of Laxatives:

Filter by:
Drug NameView by: Brand | Generic Reviews Avg. Ratings
PEG-3350 with Electolytes
generic name: polyethylene glycol 3350 with electrolytes
7 reviews
   
10
GaviLyte-G (Pro)
generic name: polyethylene glycol 3350 with electrolytes
28 reviews
   
7.8
GaviLyte-C (Pro)
generic name: polyethylene glycol 3350 with electrolytes
3 reviews
   
7.0
MoviPrep (Pro)
generic name: polyethylene glycol 3350 with electrolytes
244 reviews
   
7.0
GoLYTELY (Pro)
generic name: polyethylene glycol 3350 with electrolytes
36 reviews
   
6.8
GaviLyte-N (Pro)
generic name: polyethylene glycol 3350 with electrolytes
7 reviews
   
5.9
Colyte (Pro)
generic name: polyethylene glycol 3350 with electrolytes
2 reviews
   
5.0
NuLYTELY (Pro)
generic name: polyethylene glycol 3350 with electrolytes
4 reviews
   
3.8
TriLyte (Pro)
generic name: polyethylene glycol 3350 with electrolytes
2 reviews
   
3.5
Clenz-Lyte
generic name: polyethylene glycol 3350 with electrolytes
0 reviewsAdd rating
Plenvu
generic name: polyethylene glycol 3350 with electrolytes
0 reviewsAdd rating
Suclear (Pro)
generic name: polyethylene glycol 3350 with electrolytes
0 reviewsAdd rating

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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