Can I take Lactulose and Quinine together?

Why this happens

Lactulose is a laxative that can cause electrolyte imbalances (like low potassium) if used excessively. Quinine can affect the electrical activity of the heart (prolonging the QT interval). If potassium levels are low, this heart-related side effect of quinine is more likely to occur.

What you should do

It is generally safe to take these together at recommended doses. However, if you develop severe or persistent diarrhoea while taking lactulose, stop using it and speak to your doctor, as this can affect your mineral levels and make quinine less safe for your heart.

Important precautions

Heart rhythm disorders (e.g. Long QT syndrome)

Quinine can cause serious, potentially fatal heart rhythm problems. Do not take this if you have a history of heart rhythm issues or are taking other medicines that affect your heart rate.

Pregnancy

Do not take quinine if you are pregnant or planning to become pregnant, as high doses can cause birth defects or miscarriage. It should only be used in pregnancy if specifically prescribed by a specialist to treat malaria.

Tinnitus (ringing in the ears)

Stop taking quinine immediately and contact your doctor if you experience ringing in the ears, hearing loss, or dizziness, as these can be signs of quinine toxicity.

Galactosaemia

You must not take lactulose if you have galactosaemia, a rare genetic disorder where your body cannot process galactose.

Diabetes

If you are taking high doses of lactulose for liver disease (portal systemic encephalopathy), the sugar content may affect your blood glucose levels.

Food and drink warnings

Alcohol

It is best to avoid or strictly limit alcohol while taking these medicines. Alcohol can worsen the side effects of quinine, such as dizziness or blurred vision, and can contribute to dehydration, which may interfere with how lactulose works for constipation.

Water and Fluids

It is essential to drink plenty of fluids (such as water) while taking lactulose. This medicine works by drawing water into the bowel to soften stools; if you do not drink enough, the medicine may not work effectively and you may become dehydrated.

Grapefruit juice

Grapefruit juice can increase the amount of quinine in your blood, which may increase the risk of side effects. It is best to avoid drinking grapefruit juice while taking this medicine.

Tonic water

Tonic water contains small amounts of quinine. While the levels are low, consuming large amounts of tonic water alongside your medication could potentially increase the risk of side effects.

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.