Lactulose can take up to 48 hours to have an effect.
If you find the medicine makes you feel queasy, mix your dose with some water or fruit juice. Alternatively, take your doses with a meal.
Eating a healthy diet, drinking plenty of water and getting regular gentle exercise can all help prevent constipation.
|Type of medicine||An osmotic laxative|
|Available as||Oral liquid medicine, liquid sachets|
Constipation is a common problem. It can mean either going to the toilet less often than usual to empty your bowels, or passing hard or painful stools. Constipation can be caused by a number of things. Not eating enough fibre or not drinking enough fluid can cause constipation. Some conditions (such as pregnancy) can cause constipation, as can a lack of exercise or movement (such as being ill in bed) and some medicines.
Often, increasing the amount of fibre in your diet (such as by eating more fruit, vegetables, cereals, and wholemeal bread) and drinking plenty of water each day can effectively prevent or relieve constipation. You will have been recommended lactulose, a laxative, to help relieve constipation if you cannot increase the fibre in your diet or if this is insufficient. Lactulose works by drawing fluid into your bowel, which makes your stools softer and easier to pass. It is available on prescription, and it can also be bought without a prescription at pharmacies.
Lactulose also changes the acidity of the stools and this helps to discourage the growth of some germs (bacteria) present in the bowel. Because of this, lactulose is also prescribed for people with a liver problem called hepatic encephalopathy. If you have been prescribed it for this reason, ask your doctor if you need further information about the medicine.
Before taking lactulose
Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking lactulose it is important that your doctor or pharmacist knows:
- If you are so constipated that you think you may have a blockage.
- If you are unable to digest milk sugar (lactose intolerant).
- If you have a condition called galactosaemia, where your body cannot process galactose.
- If you are pregnant or breastfeeding. Lactulose is not known to be harmful to a baby, but while you are expecting or feeding a baby, you should only take medicines on the recommendation of a doctor.
- If it is intended for a child. This is because laxatives should only be given to children on the advice of a doctor or healthcare professional.
- If you are taking other medicines, including those available to buy without a prescription, as well as herbal and complementary medicines.
- If you have ever had an allergic reaction to this or to any other medicine.
How to take lactulose
- Before you start the treatment, read the manufacturer's printed information leaflet from the pack. It will give you more information about lactulose and will provide you with a full list of the side-effects which you may experience.
- Take lactulose exactly as your doctor tells you to, or as directed on the pack. The usual dose for constipation in an adult is 15 ml (three 5 ml spoonfuls) twice daily, although the dose you are advised to take may be different from this as it will be adjusted to suit your needs.
- If a doctor or healthcare professional has recommended lactulose for your child, check the label on the pack carefully to make sure that you give the correct dose for the age of your child.
- If you forget to take a dose, do not worry, just take the next dose when it is due. Do not take two doses together to make up for a forgotten dose.
Getting the most from your treatment
- Lactulose can take up to 48 hours to act, so it may take two or three days before you feel the full benefit. However, if after several days you do not feel your symptoms are improving, or if they get worse, you should speak with a doctor for further advice.
- It is important for you to drink plenty while you are constipated. Adults should aim to drink at least two litres (about 8-10 cups) of fluid per day. Most sorts of drink will do, but as a start, try just drinking a glass of water 3-4 times a day in addition to what you normally drink.
- Try to eat a balanced diet containing high-fibre foods such as wholemeal and wholegrain breads and cereals, fruit and vegetables, brown rice and wholemeal pasta. If you are not used to a high-fibre diet, it may be best to increase the amount of fibre you eat gradually.
- Keeping your body active will help you to keep your digestive system moving, so try to take some regular daily exercise.
- You may wish to include some foods in your diet that contain sorbitol. Sorbitol is a naturally occurring sugar. It is not digested very well and draws water into your bowel which has an effect of softening stools. Fruits (and their juices) that have a high sorbitol content include apples, apricots, gooseberries, grapes (and raisins), peaches, pears, plums, prunes, raspberries and strawberries.
- You can read more about how to prevent or treat constipation in the separate health information leaflets called Constipation (for adults) and Constipation in Children.
Can lactulose cause problems?
Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the ones which can occur with lactulose. You will find a full list in the manufacturer's information leaflet supplied with your medicine. Speak with your doctor or pharmacist if any of the following continue or become troublesome.
|Lactulose side-effects||What can I do if I experience this?|
|Excess wind (flatulence), tummy (abdominal) discomfort or cramps||These effects soon settle down as your body adjusts but if they continue or become troublesome, speak with your doctor or pharmacist for further advice|
|Feeling sick (nausea) or being sick (vomiting)||Try taking lactulose with meals, or mixing your dose with some water or fruit juice|
If you experience any other symptoms which you think may be due to the medicine, speak with your doctor or pharmacist for further advice.
How to store lactulose
- Keep all medicines out of the reach and sight of children.
- Store in a cool, dry place, away from direct heat and light.
Important information about all medicines
If you buy any medicines check with a pharmacist that they are safe to take with your other medicines.
Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.
If you are having an operation or dental treatment, tell the person carrying out the treatment which medicines you are taking.
This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.
Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy who will dispose of them for you.
If you have any questions about this medicine ask your pharmacist.
Further reading and references
Manufacturer's PIL, Duphalac 3.335 g/5 ml Oral Solution; Mylan Products Ltd, The electronic Medicines Compendium. Dated April 2018.
British National Formulary, 80th Edition (Sep 2020); British Medical Association and Royal Pharmaceutical Society of Great Britain, London.