Duphalac (Lactulose) Solution

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About Product
This content has been written and checked for quality and accuracy by
Adil Bhaloda Pharmacist GPhC: 2086262 Updated on: 11/03/2021 Next review: 11/09/2021

What is Duphalac (lactulose)?

Duphalac is a brand of lactulose – a stool-softening laxative which is available as a sweetened syrup. It is taken orally to treat constipation in adults.

Duphalac (lactulose) can bring relief from constipation symptoms and help your bowel movements return to normal. If you have previously tried a bulk-forming laxative, such as Fybogel, have not been effective.

What causes constipation?

Constipation can affect anyone at any time, though it is more likely to affect some individuals, including people with certain bowel diseases and pregnant women.

Other causes of constipation include:

  • Lack of exercise
  • Medicines (side effects)
  • Mental health (stress, anxiety or depression)
  • Not drinking enough
  • Not eating enough fibre
  • Refraining from going to the toilet

If you experience constipation regularly, it is best to speak to your doctor. They will be able to discuss with you the possible causes of your constipation, and offer appropriate treatments for relieving your constipation.

While constipation itself is usually mild, transient and disappears on its own, it can increase your risk of other health conditions including haemorrhoids (piles).

Where can I buy Duphalac online UK?

You can buy lactulose over-the-counter from pharmacies under the brand name Duphalac. If you can’t get to the pharmacy, you can buy Duphalac online from Prescription Doctor.

All items dispatched from our UK based pharmacy are packaged in discreet, plain packaging to ensure your privacy.

How Does Duphalac Work?

Duphalac contains an osmotic laxative called lactulose.

Lactulose works by drawing water from the body into the bowels, softening stools and making them easier to pass.

How long does Duphalac (lactulose) take to work?

Lactulose starts to work after taking it for 2 to 3 days.

How Long Do I Take Duphalac For?

You should take Duphalac for as long as you have constipation, or as long as your doctor recommends. It is usually taken for up to a week.

How Do I Take Duphalac (lactulose)?

While there are no specific instructions on when to take Duphalac, you should aim to take it at the same time each day.

You can take Duphalac with or without food.

Duphalac is available in 15 ml sachets or 200 ml bottles. If you buy Duphalac syrup in a bottle, you will need to measure the medicine out yourself using a measuring cup or spoon. Using a kitchen teaspoon can cause you to accidentally take the wrong dosage of Duphalac.

The amount of lactulose you take depends on the severity of your constipation and how well you respond to treatment.

Duphalac (lactulose) comes with a measuring device such as a sachet or spoon, so you can measure each dosage correctly.

It’s generally advised that you begin by drinking one 15ml sachet twice a day. You can increase the dosage to 45ml (3 sachets) a day if required. Your dose can go up or down depending on the efficacy of the medication on your body.

When taking Duphalac, do not keep the medicine in your mouth. Duphalac is high in sugar and can cause tooth decay. You should swallow the medicine immediately when taking it.

You can dilute Duphalac with water or mix it with juice if the taste it too sweet. If you mix the medicine with juice, you should drink the solution immediately.

You should aim to drink about 6 to 8 glasses of water a day while taking lactulose to prevent dehydration, which can worsen your constipation.

What should I do if I forget to take Duphalac (lactulose) when I should?

I you forget to take Duphalac at the recommended time, don’t panic – simply skip the missed dose and continue to take your next dose at the usual time. Never take more Duphalac to make up for the missed dose.

If your doctor has advised you to take Duphalac every day and you regularly forget to take it, it’s a good idea to set an alarm as a reminder.

What should I do if I take too much Duphalac (lactulose)?

If you accidentally take too much Duphalac (lactulose), it is unlikely to harm you, but it is advisable that you consult your doctor or pharmacist. You may experience side effects such as diarrhoea, stomach cramps or dehydration.

Duphalac Side Effects and Cautions

Before taking Duphalac (lactulose) for constipation, it’s important to read the patient information leaflet enclosed with your medicine. This leaflet contains important information about taking, storing and discarding the medicine.

You can view the Duphalac patient information leaflet online.

Duphalac may not be suitable for you.

Do not take Duphalac if you:

  • have galactosaemia
  • have an intestinal blockage
  • have a perforation of the gastrointestinal tract
  • are at risk of gastrointestinal perforation
  • have galactose or fructose intolerance
  • have total lactase deficiency
  • have glucose-galactose malabsorption

Speak to your doctor before taking Duphalac if you:

  • are lactose intolerant
  • have diabetes
  • suffer from unexplained stomach ache

If you are unsure whether Duphalac (lactulose) is safe for you, speak to your doctor for advice.

Side effects of Duphalac (lactulose)

All medicines have the potential of causing side effects, though not everybody who takes Duphalac will experience them. It’s important to be aware of the side effects posed by the medicine you are taking, and to keep an eye out for any changes during your course of treatment.

Common side effects of Duphalac include:

  • Abdominal pain
  • Diarrhoea
  • Flatulence (passing wind)
  • Nausea (feeling sick)
  • Vomiting

This is not an exhaustive list of side effects. Further information regarding the safety of Duphalac, including a complete list of side effects, can be found listed in the patient information leaflet enclosed with your medicine.

If you experience any side effects of taking Duphalac, regardless of whether they are listed above or in the patient information leaflet, speak to your doctor.


Do not take Duphalac if you are allergic to lactulose or any of the other ingredients listed in the patient information leaflet.

Duphalac contains lactose and fructose. Speak to your doctor before taking Duphalac (lactulose) if you have been told that you are sensitive or intolerant to some sugars.

If you experience an allergic reaction after taking Duphalac (lactulose), stop taking the medicine and go straight to your nearest accident and emergency department. Remember to take the packaging leaflet and any remaining medicine with you so that doctors treating you know exactly what you have taken.

Signs of an allergic reaction include:

  • Chest tightening
  • Dry, red and cracked skin
  • Itchy, red watery eyes
  • Raised, itchy, red rash (hives)
  • Swelling of the lips, tongue, eyes or face
  • Tummy pain, nausea, vomiting or diarrhoea
  • Wheezing

Other safety information

If you have any questions about Duphalac (lactulose) or constipation, you can send a message to our medical team for advice.

Please inform our medical team of all medicines you are currently taking, including those on prescription or bought over the counter, as well as health and herbal supplements.

While taking laxatives, it’s important to drink plenty of fluids throughout the day to prevent dehydration. You should aim to drink between 6 and 8 glasses of water daily while taking Duphalac (lactulose).

Do not take Duphalac past the expiry date printed on the packaging. The date refers to the last day of the specified month.

Never throw away medicine our household or water waste as this can harm the environment. Ask your local pharmacy if they can dispose of unwanted or expired medicine on your behalf.

Always store Duphalac out of sight and reach from children and pets.

Never share your medicine with anybody else, even if they are experiencing the same symptoms or have been diagnosed with the same condition as you.

Lactulose should not be used by those under the age of 14 unless specified by a doctor.

Frequently Asked Questions

Can I drink alcohol while taking Duphalac (lactulose)?

While lactulose is unlikely to interact with alcohol, you should avoid alcohol while treating constipation. Alcohol is a mild diuretic which causes you to lose fluids by passing urine more often.

Will Duphalac impact my ability to drive or operate machinery?

Duphalac should not impact your ability to drive or operate machinery. If you experience any side effects which may make you unsuitable to drive or operate machinery, such as dizziness or fatigue, then you should avoid such activities until you feel safe to do so.

Can I Take Duphalac While Pregnant?

Duphalac is safe to use during pregnancy and breastfeeding. However, you should always speak to your doctor before taking any medicine if you are pregnant, think you might be pregnant or breastfeeding.

Should I Avoid Any Foods or Drinks While Taking Duphalac (lactulose)?

There are no foods or drinks that need to be avoided, but it is advised that you avoid sweets, cheeses, cakes and pastry-type foods as these can cause or worsen constipation.

It is encouraged to eat more fibre to prevent and ease constipation.

Does Duphalac Affect Contraception?

Taking Duphalac (lactulose) will not directly affect your hormone contraception. However, taking too much Duphalac or taking it too often can lead to diarrhoea. If you experience severe or consistent diarrhoea over 24 hours, your contraception may be affect.

You should check the leaflet of your contraceptive pill if you suffer with ongoing diarrhoea, and use other forms of contraceptive (such as condoms) to prevent unwanted pregnancies.

Can I Take Other Medication While Taking Duphalac?

There are no known problems taking Duphalac with other medications, but you should always tell your doctor or pharmacist if you are on additional medication including supplements or herbal remedies.

Will Duphalac help me lose weight?

No, Duphalac - nor any laxative - will help you lose weight. Using laxatives as a method to lose weight is very dangerous and can lead to dehydration. If you are struggling to lose weight, you can complete an online consultation for weight loss with us.

Our medical team can help you find the most suitable treatments for weight loss.

Can I use different laxatives together?

According to the NHS, you can use a bulk-forming laxative alongside an osmotic laxative or stool softening laxative.

If you are unsure which laxatives are suitable for you, or indeed which laxatives can be used together, speak to your doctor or a pharmacist for advice.

Table of contents

What is Duphalac (lactulose)?

How Does Duphalac Work?

How Do I Take Duphalac (lactulose)?

Duphalac Side Effects and Cautions

Frequently asked questions

Treatment information

  • Product Name: Duphalac
  • Manufacturer: Mylan
  • Active Ingredient(s): Lactulose
  • Administration: Oral
  • Presentation: Liquid solution
  • Available Strength: 3.335g/5ml
  • Exemption: Pharmacy only
  • Dosage: 15-45ml (1-3 sachets) a day.
  • Description: Duphalac is an osmotic laxative which is used to treat constipation in adults.
  • Drug Class: Osmotic Laxative
  • Alcohol Consumption: Avoid or limit alcohol consumption while taking Duphalac.
  • When Pregnant: Speak to your doctor if you are pregnant or think you might be pregnant before taking Duphalac.
  • When Breastfeeding: Speak to your doctor if you are breastfeeding before taking Duphalac.
Click here to view the Duphalac (Lactulose) Solution - Patient Information Leaflet

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