What Are the Different Types of Laxatives?

Not all laxatives work in the same way. Understanding the differences between the main types can support you and your healthcare professional to choose the laxative most likely to help in your situation.

What Is the Difference Between the Types of Laxatives?

Laxatives are classified according to how they work.¹ The main categories of laxatives are bulk-forming laxatives, osmotic laxatives, stimulant laxatives, fibre supplements, stool softeners and lubricants.²

Bulk-forming laxatives are fibre products which are not absorbed by the gut, so they add bulk to stool, making bowel movements easier.² Common examples are psyllium husk and methylcellulose.¹ They must be taken with enough fluid; without it, they can cause bloating or bowel obstruction.¹

Osmotic laxatives draw water into the bowel by osmosis, making stools easier to pass.² Examples include lactulose, polyethylene glycol (PEG), and sorbitol.²

Stimulant laxatives act directly on the bowel lining and the gut’s nerve network to decrease fluid absorption and increase muscle contractions that push stool along. Examples include bisacodyl and senna.¹

Stool softeners work by increasing the amount of water and fat in the stool, making it softer and easier to pass. Docusate is a common example. They are useful for people whose stools are hard (for example, because of medicines such as prescription painkillers) or who are not very mobile (for example, during a hospital stay).²

Lubricant laxatives ease the passage of stool by lubricating the intestine. Liquid paraffin (mineral oil) is a lubricant laxative.¹ Mineral oil can used as an enema to treat fecal impaction (clearing hard, stuck stool).⁵

Fibre supplements are dietary supplements that absorb water and help maintain bowel regularity. They are useful in those who don’t consume enough fibre in their diet.²

You may come across further laxative types not detailed in this article.^3,6

Which Are Common Osmotic Laxatives?

Examples of osmotic laxatives include:

• Lactulose – a synthetic sugar that is poorly absorbed by the small intestine and passes undigested to the colon, where bacteria break it down. This makes the colon more acidic and draws in water, softening stool and stimulating bowel movements.⁷
• Polyethylene glycol (PEG) – is long-chain polymer that binds with water, thus keeping water in the stool which softens it, and increasing stool volume.^3,8
• Magnesium hydroxide (milk of magnesia) – a magnesium salt that draws water into the bowel by osmosis.¹ Long-term use is not recommended, and caution is advised in those with kidney disease.⁵
• Sorbitol – is a type of sugar alcohol that reaches the large bowel, where gut bacteria break it down. This process helps the bowel move more often and makes it easier to pass stools.⁵

What Is the Difference Between Osmotic and Stimulant Laxatives?

Osmotic and stimulant laxatives differ in how they work, how fast they act, and their side effects.⁵

Osmotic laxatives work indirectly: they draw water into the bowel, softening stool and helping the bowel’s natural movement.² They tend to act slowly, taking 24 to 48 hours to work.⁵ They can cause bloating, gas, cramping and nausea.⁵ Polyethylene glycol (PEG) has shown benefit in chronic constipation, with response durable over six months.³

Stimulant laxatives work directly, prompting the bowel contract which helps to move the stool along.² They tend to work relatively quickly, typically within 6 to 12 hours.⁵ They can cause diarrhoea and stomach pain, and are recommended only for short-term or as-needed use.^4,5 Guidelines advise caution with prolonged use because long-term data are lacking.⁵

How Is Constipation Usually Treated?

The right laxative depends on the cause of constipation, other health conditions and factors relating to the individual person.¹ For chronic constipation, guidelines such as NICE and the World Gastroenterology Organisation recommend a step-by-step approach:^4,9

1. Lifestyle. Start with lifestyle changes – healthy diet with an increase in dietary fibre, ensure adequate fluid intake, regular physical activity.⁹
2. Fibre. If lifestyle changes are not enough, a bulk-forming laxative such as psyllium is an option, particularly for people with low fibre intake.⁹
3. Osmotic laxatives. If stools remain hard or difficult to pass, then add in or switch to an osmotic laxative is recommended; PEG and lactulose are both options.⁹
4. Stimulant laxatives may be added if stools are difficult to pass or there is a sensation if inadequate emptying.⁹

Individual factors also affect the choice. These examples are not exhaustive, but give a sense of things to consider:

• Those with kidney problems should avoid using magnesium salts, because of potentially harmful effects.⁵
• Galactosaemia: patients requiring a galactose-free diet should not take lactulose.⁷
• Bulk-forming laxatives should be avoided if there is faecal impaction (hard, stuck stool).⁵

How Do I Know Which Type of Laxative Is Right for Me?

If you are unsure which laxative is right for you, your pharmacist or doctor can advise on the most appropriate option for your situation, including the laxative type, the right dose and how to use it correctly alongside any other medicines.² If your constipation is persistent, severe, or accompanied by alarm symptoms such as rectal bleeding, unexplained weight loss, or a sudden change in bowel habit, speak with a doctor before starting a laxative.⁴

Conclusion

Laxatives are not a single treatment but a family of medicines with different mechanisms, benefits and limitations.¹ A step-by-step approach can be used to manage chronic constipation, starting with lifestyle measures and bulk-forming agents before moving to osmotic and then stimulant laxatives if needed.⁹ The right choice depends on your circumstances, and a pharmacist or doctor can help you decide.²

This article provides general health information only and is not a substitute for personalised medical advice. Always consult a qualified healthcare professional before starting any new treatment.

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This article was written with the assistance of generative AI technology and reviewed for accuracy.