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Lactulose 3.335g/5ml Oral Solution – 300ml is an osmotic laxative used to relieve constipation by increasing the amount of water retained in the bowel. This helps soften hard stools, making them easier to pass and supporting more regular bowel movements.
Lactulose is a synthetic sugar that is not significantly absorbed into the bloodstream. Instead, it passes through the digestive system to the large bowel, where naturally occurring bacteria break it down into organic acids. These substances help draw water into the bowel, softening stools and encouraging bowel movement.
Unlike stimulant laxatives, which primarily act by encouraging bowel contractions, lactulose works by increasing the water content and volume of stools.
The medicine is supplied as a clear, viscous liquid that can be measured using a suitable dosing cup. It may be taken on its own or mixed with water or fruit juice.
Lactulose does not usually provide immediate relief. It can take two to three days for the full treatment effect to develop.
What Is Lactulose Oral Solution Used For?
Lactulose is used for the treatment of constipation.
Constipation may involve:
- Passing stools less frequently than usual
- Hard, dry or lumpy stools.
- Difficulty or discomfort when passing stools.
- Straining during bowel movements.
- Feeling that the bowel has not emptied completely.
- Abdominal discomfort associated with constipation.
Lactulose can be useful when stools need additional moisture to pass more comfortably.
The medicine is also licensed for the treatment of hepatic encephalopathy, a serious complication of liver disease. However, that condition requires medical supervision and different dosing. This Pharmulous listing focuses on constipation relief.
How Does Lactulose Work?
Lactulose belongs to a group of medicines known as osmotic laxatives.
After being swallowed, lactulose travels through the stomach and small intestine with very little absorption.
When it reaches the large bowel, intestinal bacteria break it down into smaller organic acids.
These acids lower the pH of the bowel contents and create an osmotic effect, drawing water into the bowel.
The additional water helps:
- Soften hard stools.
- Increase stool volume.
- Encourage normal bowel movement.
- Reduce the difficulty of passing stools.
Because this process depends on activity in the large bowel, the medicine usually takes longer to work than stimulant laxatives or glycerol suppositories.
Benefits of Lactulose Oral Solution
Relieves Constipation
Helps manage constipation by increasing the water content of stools.
Softens Hard Stools
Makes dry or hard stools easier to pass.
Supports Bowel Regularity
Can help restore a more comfortable bowel pattern.
Liquid Formulation
Offers an alternative to tablets, capsules and sachets.
Flexible Measuring
A suitable measuring device allows the dose to be adjusted according to the product instructions and individual response.
Can Be Diluted
May be taken on its own or mixed with water or fruit juice.
How Long Does Lactulose Take to Work?
Lactulose generally takes two to three days to produce its full effect.
Some people may notice changes sooner, but it should not be expected to work immediately.
Taking more than the recommended amount will not necessarily produce faster relief and may increase the risk of diarrhoea, abdominal pain and dehydration.
If constipation does not improve after several days, consult a pharmacist or doctor.
Who Can Take Lactulose?
Lactulose can be used by adults and older people according to the product instructions.
It also has licensed paediatric doses, but children should only receive laxatives under medical supervision.
The correct dose depends on age, symptoms and the specific product.
Pregnant and breastfeeding patients may be able to use lactulose when appropriate, as very little reaches the bloodstream.
Lactulose vs Other Constipation Treatments
Different laxatives work in different ways.
Lactulose is an osmotic laxative that increases water retention in the bowel.
Laxido and Movicol contain macrogol-based osmotic laxatives. Like lactulose, they increase water within stools, but their active ingredients and formulations differ.
Fybogel contains ispaghula husk, a bulk-forming laxative that absorbs water and increases stool bulk.
Dulcolax tablets contain bisacodyl, a stimulant laxative that encourages bowel contractions.
Senokot contains senna-derived stimulant laxatives.
DulcoEase contains docusate sodium, which helps water penetrate hard stools.
Glycerol suppositories are inserted into the rectum and act locally to encourage bowel emptying.
The most appropriate product depends on the cause of constipation, how quickly relief is needed and individual medical circumstances.
Can Lactulose Cause Wind or Bloating?
Yes. Wind and bloating can occur, particularly when treatment first begins.
This happens because bacteria in the large bowel break down lactulose, producing gas as part of the process.
For many people, the increased wind improves after a few days.
If bloating is severe, persistent or accompanied by significant pain, seek medical advice.
When Should Lactulose Not Be Used?
Do not take this medicine if you:
- Are allergic to lactulose or any related sugars present in the formulation.
- Have galactosaemia, a rare inherited condition affecting galactose metabolism.
- Have a known or suspected intestinal obstruction.
- Have a digestive tract perforation or are at risk of perforation.
- Have certain rare inherited sugar-intolerance or absorption disorders listed in the product leaflet.
Seek medical advice before treatment if you have unexplained abdominal pain.
Important Precautions
Lactulose may contain small amounts of lactose, galactose and other related sugars from its manufacturing process.
People with certain inherited sugar disorders must not take it.
People with diabetes should consider the sugar content, particularly if using higher doses for a medical condition other than constipation.
Prolonged use of excessive doses can cause diarrhoea and disturbances in the body's fluid and electrolyte balance.
If you need laxatives regularly or for a long period, speak to a healthcare professional.
Supporting Healthy Bowel Habits
Constipation treatment may be more effective when combined with appropriate lifestyle measures.
These include eating a balanced diet containing fibre, drinking sufficient fluids, remaining physically active and allowing time for regular toilet visits.
A healthcare professional can advise if constipation is persistent, recurrent or related to another medical condition.
Active Ingredient
Lactulose – 3.335g per 5ml
Each 5ml of oral solution contains 3.335g lactulose.
Lactulose is a synthetic disaccharide that works as an osmotic laxative.
It is broken down by bacteria in the large bowel, increasing the water content of stools and helping relieve constipation.
Other Ingredients
The Bristol Laboratories formulation does not contain additional excipients.
However, the solution may contain small amounts of related sugars remaining from the manufacturing process, including:
- Lactose.
- Galactose.
- Fructose.
- Tagatose.
- Epilactose.
These are manufacturing residues rather than separately added flavourings or preservatives.
Important Allergy and Sugar Information
Galactosaemia
Do not take lactulose if you have galactosaemia.
Hereditary Sugar Intolerances
People with certain rare inherited conditions involving galactose or fructose intolerance, total lactase deficiency or glucose-galactose malabsorption should not take this medicine.
Lactose Intolerance
Lactulose may contain lactose. Ask a pharmacist or doctor if you have significant lactose intolerance.
Diabetes
The usual doses used for constipation are generally unlikely to cause a problem for most people with diabetes. However, the solution contains related sugars, and higher doses require additional consideration.
No Added Flavourings
This formulation is an unflavoured oral solution.
Always check the ingredients of the exact product supplied.
Adults and Adolescents
Starting dose: 15–45ml daily.
Maintenance dose: 15–30ml daily.
The daily dose may be taken once a day or divided into two doses.
After a few days, the dose may be adjusted according to the response and product instructions.
Children Aged 7–14 Years
Starting dose: 15ml daily.
Maintenance dose: 10–15ml daily.
Children should only use lactulose under medical supervision.
Children Aged 1–6 Years
Usual dose: 5–10ml daily.
A healthcare professional should determine whether lactulose is appropriate and advise on the correct dose.
Infants Under 1 Year
Licensed dose: Up to 5ml daily.
Laxatives in infants should only be used under medical supervision.
Do not give lactulose to a baby without medical advice.
- How to Take Lactulose Oral Solution
- Read the label and Patient Information Leaflet before use.
- Measure the prescribed or recommended amount using a suitable oral measuring device.
- Swallow the dose in one go.
- Take it on its own or dilute it with water or fruit juice.
- If taking a single daily dose, try to take it at approximately the same time each day.
- Drink adequate fluids throughout the day.
- Adjust the dose only in accordance with the leaflet or advice from a healthcare professional.
Do not use an ordinary household spoon to measure medicine.
Should Lactulose Be Taken Before or After Food?
Lactulose can generally be taken with or without food.
If taking one daily dose, it may be convenient to take it at breakfast.
Consistency in timing can make treatment easier to follow.
How Much Water Should You Drink?
During laxative treatment, the product information recommends approximately 1.5–2 litres of fluid daily, equivalent to around six to eight glasses, unless a healthcare professional has advised you to restrict fluids.
Adequate hydration supports bowel function and helps reduce the risk of dehydration if diarrhoea occurs.
How Long Can You Take Lactulose?
The duration depends on the reason for treatment and individual response.
Long-term use without medical supervision is not recommended.
If constipation persists despite several days of treatment, or if you need a laxative regularly, consult a pharmacist or doctor.
What If You Miss a Dose?
If you forget a dose, take your next dose at the usual time.
Do not take a double dose to make up for a forgotten dose.
Can You Take Lactulose With Other Medicines?
The Bristol Laboratories SmPC notes a theoretical interaction with certain modified-release mesalazine preparations, although a study did not demonstrate an effect in healthy volunteers.
Tell a pharmacist or doctor about any other medicines you take, especially if you use other laxatives, diuretics or treatments that affect electrolyte balance.
Pregnancy
Lactulose may be used during pregnancy when considered necessary by a healthcare professional.
Because very little lactulose is absorbed into the bloodstream, significant effects on the unborn baby are not expected.
Ask a pharmacist, doctor or midwife for advice if you are pregnant or planning pregnancy.
Breastfeeding
Lactulose can be used during breastfeeding.
Very little is absorbed into the mother's bloodstream, so significant exposure to the breastfed baby is not expected.
Storage Instructions
For the Bristol Laboratories formulation:
- Store below 25°C.
- Do not use after the expiry date printed on the bottle.
- Use within 12 months of first opening.
- Keep the bottle closed when not in use.
- Keep out of the sight and reach of children.
Storage instructions may differ between manufacturers. Always follow the label on the supplied bottle.
Like all medicines, Lactulose Oral Solution can cause side effects, although not everyone experiences them.
The most common effects involve the digestive system.
Very Common Side Effects
Diarrhoea
Diarrhoea may affect more than 1 in 10 people taking lactulose.
It is more likely if the dose is higher than needed.
If diarrhoea occurs, reduce the dose according to the leaflet or seek advice from a healthcare professional.
Persistent diarrhoea can cause dehydration and electrolyte imbalance.
Common Side Effects
These may affect up to 1 in 10 people.
Flatulence (Wind)
Increased wind is common, especially during the first few days of treatment.
It usually improves as the body adjusts.
Abdominal Pain
Some people experience stomach pain or cramps.
Seek medical advice if the pain is severe, persistent or unexplained.
Nausea
Lactulose may cause a feeling of sickness.
Taking the medicine diluted with water or juice may make it easier to tolerate.
Vomiting
Vomiting is another possible side effect.
If vomiting is persistent or associated with severe abdominal pain, seek medical assessment.
Uncommon Side Effects
Electrolyte Imbalance
Electrolyte disturbances may occur as a consequence of diarrhoea.
This is more likely with excessive dosing, prolonged use or significant fluid loss.
Symptoms can include weakness, dizziness, muscle cramps or an irregular heartbeat.
Seek medical advice if these occur.
Side Effects With Unknown Frequency
Allergic Reactions
Hypersensitivity reactions have been reported.
Skin Rash
Some people may develop a rash.
Itching
Itching, also known as pruritus, may occur.
Hives
Raised, itchy skin patches called urticaria have been reported.
Stop taking lactulose and seek medical advice if you develop a suspected allergic reaction.
Seek emergency medical help if you experience difficulty breathing or swelling of the face, lips, tongue or throat.
What Happens If You Take Too Much Lactulose?
Taking too much may cause:
- Diarrhoea.
- Abdominal pain.
- Excessive fluid loss.
- Electrolyte disturbances.
If you take more than directed, reduce or stop treatment as advised and seek medical advice if symptoms are significant.
When Should You Stop Taking Lactulose?
Stop treatment and seek medical advice if you experience:
- Severe or persistent abdominal pain.
- Persistent vomiting.
- Severe diarrhoea.
- Signs of dehydration.
- An allergic reaction.
- Constipation that worsens or does not improve after several days.
Reporting Side Effects
Suspected side effects can be reported through the MHRA Yellow Card Scheme:
Frequently asked questions
What is Lactulose Oral Solution used for?
Lactulose is an osmotic laxative used to relieve constipation.
It helps retain water in the bowel, softening stools and making them easier to pass.
How does lactulose work?
Lactulose passes into the large bowel, where bacteria break it down into organic acids.
These substances help draw water into the bowel and encourage normal bowel movement.
How long does lactulose take to work?
Lactulose generally takes two to three days to produce its full effect.
It is not intended for immediate constipation relief.
How much lactulose should adults take?
For the Bristol Laboratories formulation, the adult starting dose is 15–45ml daily.
The usual maintenance dose is 15–30ml daily.
Follow the leaflet or advice from your pharmacist or doctor.
Should lactulose be taken before or after food?
Lactulose can generally be taken with or without food.
If taking it once daily, you may find it convenient to take it during breakfast.
Can I take lactulose during pregnancy?
Lactulose may be used during pregnancy when considered necessary by a healthcare professional.
Ask a pharmacist, doctor or midwife for advice.
Can I take lactulose while breastfeeding?
Yes. Lactulose can be used during breastfeeding because very little is absorbed into the bloodstream.
Is lactulose suitable for people with diabetes?
The usual constipation doses are generally unlikely to cause a significant problem for most people with diabetes.
However, lactulose contains small amounts of related sugars. Ask a healthcare professional if you have concerns about blood glucose control.
