Can I take Amitriptyline and Lactulose together?
Drug interaction guide
Originally published 25 Jan 2026
Meets Patient’s editorial guidelines
- DownloadDownload
- Share
- Language
- Discussion
- Audio Version
- Add to preferred sources on Google
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.
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
It 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.
Important precautions
Suicidal 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
Alcohol
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.
Using other medicines
Taking 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.
Patient picks for Drug interactions

Drug interactions checker
Can I take Metformin and Ibuprofen together?
Taking ibuprofen while on metformin can increase the risk of kidney problems and a rare but serious condition called lactic acidosis. Ibuprofen can also make metformin stay in your body longer, potentially increasing its side effects.

Drug interactions checker
Can I take Ashwagandha and Vitamin B12 together?
There are no known clinical interactions between ashwagandha and vitamin B12. It is generally considered safe to take these two supplements together.
Article history
The information on this page is written and peer reviewed by qualified clinicians.
Article also available in English, German, Spanish, French, Italian, Portuguese, Hindi, Hebrew, Arabic, and Swedish.
25 Jan 2026 | Originally published

Ask, share, connect.
Browse discussions, ask questions, and share experiences across hundreds of health topics.

Feeling unwell?
Assess your symptoms online for free
Sign up to the Patient newsletter
Your weekly dose of clear, trustworthy health advice - written to help you feel informed, confident and in control.
By subscribing you accept our Privacy Policy. You can unsubscribe at any time. We never sell your data.
More in drug interactions checker
- Can I take Apixaban and Tramadol together?
- Can I take Atorvastatin and Cardioace together?
- Can I take Atorvastatin and Levothyroxine together?
- Can I take Biotin and Vitamin D together?
- Can I take Candesartan and Cod liver oil together?
- Can I take Candesartan and Mirtazapine together?
- Can I take Citalopram and Co-codamol together?
- Can I take Clopidogrel and Naproxen together?
- Can I take Colecalciferol and Fexofenadine together?
- Can I take Folic acid and Glucosamine together?
- Can I take Glucosamine and Vitamin D together?
- Can I take Iron supplements and Prozac together?
- Can I take Iron supplements and Vitamin D together?
- Can I take Losartan and Turmeric together?
- Can I take Mirtazapine and Sertraline together?
- Can I take Mounjaro and Metformin together?
- Can I take Pregabalin and Sedoxil together?
- Can I take Pregabalin and Sertraline together?
- Can I take Sertraline and Citalopram together?
- Can I take Vitamin B12 and Vitamin C together?