The Science Behind Laxatives: Key Ingredients And How They Work

Laxatives are a type of medication used to treat and prevent constipation and other gastrointestinal issues. They work by loosening stools and increasing bowel movements. There are several types of laxatives, including bulk-forming laxatives, osmotic laxatives, stimulant laxatives, and lubricant laxatives, which differ in their mechanisms of action and onset of effects. While laxatives can provide relief for constipation, they may also cause side effects such as abdominal pain, nausea, and diarrhoea. It is important to consult a healthcare professional before using laxatives and to prioritise lifestyle changes, such as increasing fibre and fluid intake, over laxative use.

Bulk-forming laxatives: Made from plants, these laxatives form a watery gel in the intestines, making it easier to pass stools

Bulk-forming laxatives are a type of medicine that treats constipation. They are made from plants and work by absorbing liquid in the intestines, creating a softer, more liquid-like stool that is easier to pass. This type of laxative includes psyllium (Metamucil), polycarbophil (FiberCon), and methylcellulose (Citrucel). They are different from other types of laxatives like stimulant laxatives, which speed up the movement of bowels through the intestines, and lubricant laxatives, which lubricate the stools.

Bulk-forming laxatives are often the first line of defence against constipation, as they usually provide a more gradual improvement of symptoms. They are also generally safer than other types of laxatives, with a lower risk of side effects such as cramping or explosive diarrhoea. However, they can still cause mild stomach pain, bloating, or gas, and people with allergies to psyllium should be cautious. It is important to take bulk-forming laxatives with plenty of water to prevent bowel obstruction and stay well-hydrated throughout the day.

These laxatives are typically available over the counter in pharmacies and supermarkets, but they can also be prescribed by a doctor. They usually take 2 to 3 days to work and should only be taken occasionally for up to a week at a time. If constipation persists or worsens, it is recommended to consult a healthcare professional.

To prevent constipation in the first place, it is advisable to maintain a healthy lifestyle with a high-fibre diet, regular exercise, and adequate fluid intake.

Osmotic laxatives: These draw water into the intestines, softening stools and aiding their passage

Osmotic laxatives are a type of medication used to treat or prevent constipation. They work by drawing water into the colon, softening the stool, and making it easier to pass. This type of laxative is particularly useful for those who do not consume enough water. Osmotic laxatives are also used for bowel preparation before a colonoscopy.

Osmotic laxatives are available over the counter and by prescription. They include:

• Polyethylene glycol (PEG): an organic compound derived from petroleum that can be safely ingested to manage constipation. PEG is tasteless and odourless and is typically mixed with water or other fluids before consumption. It is available over the counter under brand names such as Miralax and GlycoLax.
• Lactulose: a synthetic sugar solution that acts as an osmotic laxative by drawing water into the colon and promoting the growth of beneficial bacteria. It is often prescribed to treat chronic constipation and hepatic encephalopathy. Lactulose-containing laxatives are available by prescription under brand names such as Cephulac, Duphalac, Kristalose, and others.
• Sorbitol: a non-absorbable sugar with an action similar to lactulose. Sorbitol is available over the counter and by prescription under brand names such as Arlex and GeriCare.
• Magnesium citrate: magnesium in salt form combined with citric acid. The salts help draw water into the colon. Magnesium citrate is available over the counter under brand names such as Citrate of Magnesia, Citroma, and LiquiPrep.
• Magnesium hydroxide: a milder form of magnesium sold under the brand name Milk of Magnesia. Milk of Magnesia is available over the counter and is also used as an antacid.

Osmotic laxatives can cause side effects such as nausea, bloating, cramping, flatulence, and diarrhoea. Overuse of these laxatives can lead to dehydration and the loss of electrolytes like sodium, calcium, and potassium. Therefore, it is important to follow the dosing instructions carefully and only use a laxative when needed.

Lubricant laxatives: Oily substances that coat the intestines, helping stools move through more quickly

Lubricant laxatives are a type of laxative that uses oily substances to coat the intestines and help stools move through more quickly. They are typically used as a short-term cure for constipation. Lubricant laxatives include mineral oil, which can be purchased over the counter in liquid or enema form.

Lubricant laxatives work by adding a slick layer of oil to the walls of the intestines, preventing stools from drying out and making them slippery. This allows stools to slide through the colon more easily. Lubricant laxatives also prevent the colon from absorbing water from the stool, keeping it soft.

While lubricant laxatives can be effective in providing relief from constipation, they should be used with caution. Mineral oil, for example, can interfere with the absorption of fat-soluble vitamins and decrease the absorption of certain prescription drugs. It can also cause pneumonia if inhaled. Therefore, it is recommended to only use mineral oil for a few days and to wear a protective pad to absorb any leakage. It is also important not to take mineral oil at the same time as other medications or supplements.

Lubricant laxatives are generally safe and well-tolerated, but they should not be used regularly or for an extended period. Overuse of laxatives can lead to side effects such as bloating, gas, stomach cramps, and dehydration.

Stimulant laxatives: Fast-acting laxatives that stimulate the intestines to have a bowel movement

Stimulant laxatives are one of the fastest-acting types of laxatives. They trigger the intestines to contract and push out stools, providing relief for constipation. The active ingredients in these laxatives are typically senna (also known as sennosides) or bisacodyl.

Stimulant laxatives are available in various forms, such as liquids, powders, chewables, tablets, and suppositories. Some common brand names include Senexon, Fletcher's Castoria, Senokot, Black Draught, Feen-A-Mint, Correctol, Dulcolax, and Carter's Little Pills.

These laxatives are effective in treating constipation by stimulating intestinal muscles to contract rhythmically, which helps push out a bowel movement. However, they should be used with caution as they can be habit-forming. It is recommended to consult a doctor before using stimulant laxatives, especially if you have any health conditions, are pregnant, or are breastfeeding. Additionally, they should not be used for more than a week unless specifically advised by a healthcare professional.

Side effects of stimulant laxatives may include abdominal pain, brownish-red urine, and allergic reactions. They can also cause intestinal blockage and are not recommended for children under six years old without a pediatrician's instruction.

Saline laxatives: Magnesium-based laxatives that pull water into the intestines

Saline laxatives, including magnesium-based laxatives, are a type of osmotic laxative. Osmotic laxatives work by drawing water into the intestines from the surrounding tissues, making it easier for stool to pass. This type of laxative is often recommended for people who need quick relief from constipation.

Saline laxatives, such as magnesium citrate or milk of magnesia, are typically used to clean the stool from the intestines before surgery or certain bowel procedures, such as a colonoscopy. They can also be used for the relief of constipation. However, milder products such as stool softeners or bulk-forming laxatives should be used whenever possible for constipation.

Magnesium-based laxatives are thought to work by increasing fluid in the small intestine, resulting in a bowel movement within 30 minutes to 3 hours. They are generally safe and well-tolerated, but it is important to drink a full glass of water (8 ounces or 240 milliliters) after taking this type of laxative to prevent serious side effects such as dehydration.

It is important to note that overuse of magnesium-based laxatives can lead to laxative dependence, where the body becomes unable to have a bowel movement without the use of the product. Other possible side effects include abdominal pain, decreased weight, weakness, and diarrhoea. Therefore, it is recommended to consult a healthcare professional before taking any laxatives to ensure proper usage and avoid potential interactions or complications.

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