Laxatives: What They Are And How They Work

Laxatives are a type of medicine used to treat constipation. They are often used if lifestyle changes, such as increasing fibre intake, drinking more fluids, and exercising, have not helped. Laxatives work by softening stools or stimulating the bowels to get moving. They come in various forms, including pills, capsules, liquids, suppositories, and enemas, and can be bought over the counter or with a prescription. While they are effective in treating constipation, they should be used sparingly and occasionally as they can cause side effects such as bloating, gas, and stomach cramps.

Bulk-forming laxatives

These laxatives are considered the gentlest type and are the least likely to cause side effects. They are often recommended as the first line of treatment before trying other types of laxatives. They are also preferred due to the more gradual improvement of constipation symptoms, reducing the risk of cramping or explosive diarrhoea that could occur with stimulant laxatives.

It is important to note that bulk-forming laxatives should be taken with at least 8 ounces of water or fruit juice to prevent bowel obstruction. Staying well-hydrated throughout the day is crucial. Additionally, it may take 12 hours to up to 3 days to feel relief from constipation after taking these laxatives.

While bulk-forming laxatives are generally safe, some side effects or drug interactions may occur, such as difficulty swallowing, a feeling of a lump in the throat, or difficulty breathing. Mild stomach pain, bloating, or gas may also be experienced. People with kidney disease or diabetes are at a higher risk of electrolyte imbalances when taking laxatives, so it is important to consult a doctor before use.

Osmotic laxatives

Some common osmotic laxatives include:

• Polyethylene glycol (PEG): This is an organic compound derived from petroleum that is tasteless, odourless, and typically mixed with water or other fluids. It is available over the counter under brand names like Miralax and GlycoLax.
• Lactulose: This is a synthetic sugar solution that acts as an osmotic laxative by drawing water into the colon. It is often prescribed to treat chronic constipation and hepatic encephalopathy. It is available by prescription under brand names like Cephulac, Duphalac, and Kristalose.
• Sorbitol: This is a non-absorbable sugar that has a similar action to lactulose. It is available in both over-the-counter and prescription versions, such as Arlex and GeriCare.
• Magnesium citrate: Magnesium citrate is a salt form of magnesium combined with citric acid. It helps draw water into the colon and is available over the counter as Citrate of Magnesia, Citroma, and LiquiPrep.
• Magnesium hydroxide: Also known by the brand name Milk of Magnesia, this milder form of magnesium is available over the counter and is also used as an antacid.

It is important to drink plenty of water while taking osmotic laxatives to improve their efficiency and reduce the possibility of side effects such as gas, cramps, nausea, bloating, and diarrhoea. Overuse of osmotic laxatives can lead to dehydration and other complications.

Lubricant laxatives

Like other types of laxatives, lubricant laxatives may cause side effects such as leakage from the rectum, especially at high doses. This may cause discomfort and soiling of clothes. Lowering or dividing the dose may help reduce this problem. It is important to follow the instructions and not exceed the recommended dosage to minimise the risk of side effects.

Before taking any laxative, including lubricant laxatives, it is advisable to consult a doctor or pharmacist, especially for individuals with certain health conditions or those who are pregnant or breastfeeding. While laxatives can provide relief from constipation, they are not a substitute for maintaining a healthy lifestyle, including a fibre-rich diet, adequate fluid intake, and regular exercise, which are often the first recommended approaches to addressing constipation.

Stimulant laxatives

It is important to follow the directions on the label when taking stimulant laxatives, and they should not be used for more than a week unless specifically advised by a doctor. They can be habit-forming, and prolonged use can lead to dependence and harm the bowels. Side effects of stimulant laxatives may include stomach pain or cramping, nausea, diarrhoea, and weakness. It is recommended to consult a doctor if you experience any serious side effects or if your condition worsens.

Prescription laxatives

Guanylate Cyclase-C Agonist:

Guanylate cyclase-C agonist laxatives, such as Plecanatide (Trulance), are typically prescribed for individuals suffering from chronic idiopathic constipation and irritable bowel syndrome with constipation. This medication alters stool consistency by increasing the amount of water in the gastrointestinal lumen, promoting regular bowel function. However, it is not recommended for patients under six years of age due to the risk of severe dehydration.

Linaclotide (Linzess):

Linaclotide is a prescription laxative that works by drawing water into the intestines, softening stools, and speeding up their movement. This medication is often prescribed to individuals experiencing chronic constipation. However, it is important to note that Linaclotide may cause side effects like diarrhoea.

Lubiprostone (Amitiza):

Amitiza is another prescription laxative that shares a similar mechanism of action with Linaclotide, as it also draws water into the intestines and accelerates stool movement. However, Amitiza is specifically approved for use in women.

Lactulose (Duphalac, Lactugal):

Lactulose is an osmotic laxative that pulls water into the bowel, softening stools and making them easier to pass. It is often prescribed for individuals with chronic constipation. It typically takes two to three days for Lactulose to take effect.

Methylnaltrexone (Relistor):

Methylnaltrexone is a prescription laxative used to treat opioid-induced constipation. It belongs to a class of drugs known as peripherally acting mu-opioid receptor antagonists, which work by restoring the function of the enteric nervous system. This medication is typically recommended when other treatments have not been effective.

Naloxegol (Movantik):

Naloxegol is another prescription laxative used to manage opioid-induced constipation. It acts by blocking mu-opioid receptors in the gastrointestinal tract, helping to restore normal bowel function.

Naldemedine (Symproic):

Naldemedine is also prescribed to treat constipation caused by opioid use. It works by blocking mu-opioid receptors in the gastrointestinal tract, similar to Naloxegol.

It is important to remember that prescription laxatives should only be taken under medical supervision and after consulting with a healthcare professional. These medications are typically reserved for cases where over-the-counter options have proven ineffective or for individuals with specific health conditions that require specialised treatment.

Frequently asked questions