Lactulose: A Bulk-Forming Laxative Solution?

Laxatives are a type of medicine used to treat constipation. There are four main types of laxatives: bulk-forming, osmotic, stimulant, and poo-softener laxatives. Lactulose is a type of osmotic laxative, which works by drawing water from the body into the bowel to soften stool and make it easier to pass. Bulk-forming laxatives, on the other hand, increase the weight of the stool, stimulating the bowel.

How does lactulose work?

Lactulose is a synthetic sugar used to treat constipation. It is a laxative, specifically an osmotic laxative, that works by drawing water from the body into the colon to soften stools and make them easier to pass. It is also used to treat hepatic encephalopathy, a condition where the liver fails to clear toxins properly, leading to problems in the brain. This medication can be taken by mouth or rectally, and it is typically used once a day for constipation and three to four times a day for liver disease.

Lactulose is broken down in the colon by bacteria into monosaccharides, volatile fatty acids, hydrogen, and methane. This process reduces intestinal transit time and pH, creating a laxative effect. Additionally, it promotes increased ammonia uptake by colonic bacteria, which utilise the trapped ammonia as a nitrogen source for protein synthesis. Lactulose also inhibits intestinal glutaminase activity, blocking the intestinal uptake of glutamine and reducing ammonia production.

Lactulose is generally well-tolerated, but side effects may include gas, bloating, burping, stomach rumbling, nausea, and cramps. It is important to note that lactulose is not suitable for everyone, especially those with certain health conditions like Crohn's disease or ulcerative colitis. It should also be used with caution in individuals with diabetes, as it may affect blood sugar levels.

Lactulose is typically taken orally, but it can also be administered rectally as an enema for liver disease. It usually takes a couple of days for lactulose to work, and it is recommended to consult a doctor if constipation persists after three days. While lactulose is effective in treating constipation, it is important to prioritise lifestyle changes such as increasing fibre intake, drinking plenty of water, and exercising regularly to prevent constipation.

How long does it take to work?

Lactulose is a type of laxative called an osmotic laxative. It is broken down in the bowel into substances that pull water out from the body and into the bowel to soften stools and make them easier to pass. It is typically taken two to four times a day.

Lactulose usually produces a bowel movement within 24 to 48 hours of consumption. However, it can take up to two days to work and make you have a bowel movement. If you need constipation relief more quickly, faster options are available.

If you are still constipated after three days, talk to your doctor. Ideally, you will only take lactulose occasionally and for a few days at a time. Using lactulose for longer can lead to diarrhoea and an electrolyte imbalance.

What are the side effects?

Lactulose is a type of laxative called an osmotic laxative. It is not a bulk-forming laxative. Bulk-forming laxatives increase the "bulk" or weight of poo, which in turn stimulates the bowel. They are usually tried first before trying a laxative like lactulose.

Like all medicines, lactulose may cause side effects in some people, but many people have no side effects or only minor ones. Here are some of the possible side effects of taking lactulose:

Common side effects

• Diarrhoea, particularly at high doses. This occurs in more than 1 in 10 people.
• Wind (farting and burping).
• Feeling sick (nausea).
• Being sick (vomiting).

Serious side effects

These occur rarely (less than 1 in 100 people).

• Severe diarrhoea or vomiting for more than a couple of days, along with muscle cramps or weakness and an irregular heartbeat. These could be signs of an electrolyte imbalance, where levels of substances like sodium, potassium and magnesium in the body get too high or too low.
• Serious allergic reaction (anaphylaxis). Signs of this include:
• Swelling of the lips, mouth, throat or tongue.
• Difficulty breathing.
• Tightness in the throat or difficulty swallowing.
• Discolouration of the skin, tongue or lips.
• Feeling very confused, drowsy or dizzy.
• Fainting.
• Rash that is swollen, raised, itchy, blistered or peeling.

Who should not take lactulose?

Lactulose is a type of laxative called an osmotic laxative. It is used to treat constipation and prevent complications of liver disease (hepatic encephalopathy). It is important to note that lactulose is not suitable for everyone, and there are certain individuals who should not take it.

Firstly, people with irritable bowel syndrome (IBS) are advised against taking lactulose. This is because lactulose increases gas and bloating in the stomach, which can exacerbate IBS symptoms.

Secondly, lactulose may not be suitable for those with diabetes. While it typically does not affect blood sugar levels when taken in normal doses for constipation, higher doses or long-term use may impact blood sugar levels. Therefore, individuals with diabetes should consult their doctor or pharmacist to determine if lactulose is appropriate for them.

Additionally, lactulose should be used with caution in pregnant women and breastfeeding mothers. Pregnant women should only use lactulose when clearly needed and after discussing the risks and benefits with their doctor. It is unknown if lactulose passes into breast milk, so mothers are advised to consult a doctor before breastfeeding while taking lactulose.

Furthermore, individuals with certain allergies or medical conditions should proceed with caution. Those with a low galactose diet or a history of bowel obstruction should inform their doctor or pharmacist before taking lactulose. It is also important to disclose all medications, herbal products, and dietary supplements to ensure safe and effective use of lactulose.

Lastly, lactulose is not usually recommended for children unless advised by a doctor. It is important to read the patient information leaflet and consult a healthcare professional to ensure lactulose is safe and suitable for your individual needs.

What are the alternatives?

There are several alternatives to bulk-forming laxatives, which work by increasing the "bulk" or weight of the stool, and these include osmotic, stimulant, and surface-wetting laxatives.

Osmotic laxatives, such as lactulose, draw water from the rest of the body into the bowel to soften the stool and make it easier to pass. These can be bought over the counter under brand names such as Duphalac and Lactugal. Other osmotic laxatives include macrogol, which is available under the brand names Movicol, Laxido, CosmoCol, Molaxole, and Molative.

Stimulant laxatives speed up the bowels by stimulating the nerves that control the muscles lining the gut. Examples of these include senna and bisacodyl, which are available under the brand names Senokot and Dulcolax, respectively. These are usually tried after a bulk-forming laxative has not worked.

Surface-wetting laxatives, such as arachis oil and docusate, allow water to get into the stool to soften it and make it easier to pass.

In addition to these different types of laxatives, there are also self-help alternatives to laxatives, which include:

• Increasing your daily intake of fibre—aim for about 30g of fibre per day. High-fibre foods include fruits, vegetables, and cereals.
• Adding bulking agents, such as wheat bran, oats, or linseed, to your diet. These will help to soften the stool and make it easier to pass, although they can sometimes make bloating worse.
• Drinking plenty of water to keep the stool soft.
• Exercising regularly to keep the body and gut active.

Frequently asked questions