Can I take Amitriptyline and Lactulose together?
Drug interaction guide
Originally published 25 Jan 2026
Meets Patient’s editorial guidelines
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Amitriptyline can cause constipation as a side effect. This may make lactulose (a laxative) less effective or mean you need a higher dose to see results.
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Why this happens
Amitriptyline has 'anticholinergic' effects, which slow down the movement of the digestive system. Lactulose works by drawing water into the bowel to encourage movement. These two medications essentially work against each other regarding bowel habits.
What you should do
Back to contentsIt is safe to take these together, but be aware that the amitriptyline might be the cause of your constipation. If your constipation does not improve with lactulose, speak to your doctor or pharmacist about adjusting your dose or trying a different type of laxative.
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Important precautions
Back to contentsSuicidal thoughts and mood changes
Amitriptyline can increase the risk of suicidal thoughts or self-harm, particularly when first starting treatment or changing doses. Seek immediate medical help if your mood changes or you feel depressed.
Heart conditions
Do not take amitriptyline if you have recently had a heart attack or have serious heart rhythm problems (such as heart block), as it can affect your heart rate and rhythm.
Galactosaemia or bowel obstruction
You must not use lactulose if you have a rare condition called galactosaemia (inability to process galactose) or if you have a complete blockage in your bowel.
Food and drink warnings
Back to contentsAlcohol
Drinking alcohol while taking amitriptyline can make you feel very sleepy and unsteady on your feet. It is best to avoid alcohol, especially when you first start treatment or if your dose is increased.
Caffeine (Coffee, Tea, Energy Drinks)
Amitriptyline can sometimes cause a fast or irregular heartbeat. High amounts of caffeine can worsen this effect and may also interfere with the medicine's ability to help you sleep.
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Using other medicines
Back to contentsTaking multiple medicines? Our Medicines Interaction Checker helps you check whether your prescriptions, over-the-counter medicines, and supplements are safe to take together. Simply search for your medicines to see potential interactions and what to do about them.
Disclaimer
This information is for general educational purposes only and should not be relied upon as a substitute for professional medical advice. Always consult your GP, pharmacist, or another qualified healthcare professional before making decisions about your medications. Individual circumstances may vary, and only a healthcare professional who knows your medical history can provide personalised guidance.
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Article history
The information on this page is written and peer reviewed by qualified clinicians.
25 Jan 2026 | Originally published
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