What to Know About Tonic Water and Restless Legs Syndrome

Restless legs syndrome (RLS) causes uncomfortable sensations in the legs. It can also cause the irresistible urge to move the legs. This often happens in the afternoon or nighttime when a person is lying down or sitting. It can be very disruptive, especially when it happens at night. This can lead to daytime exhaustion and sleepiness.¹

Nighttime leg cramps are common. They affect one-third of people over 60 from time to time. More than half of people over 80 experience them from time to time. Quinine has often been used to treat these leg cramps. Years ago, doctors often prescribed quinine pills. They also told people to drink tonic water because of its high levels of quinine.²

Tonic water and quinine

These days, drinking tonic water might seem like a natural way to treat RLS. One liter of tonic water usually contains no more than 83 mg of quinine. A normal dose of quinine pills contains about 500 to 1000 mg of quinine. Drinking a liter of tonic water each day is unlikely to help RLS symptoms. There are also risks to taking large amounts of quinine, especially for long periods of time.³

In fact, the U.S. Food and Drug Administration (FDA) has been warning people about the dangers of quinine since 1994. In 2006, the FDA told people to stop using quinine for leg cramps. This is because there is a chance that quinine can cause serious side effects or death.^2,4

Learning about the possible dangers and interactions of quinine can help you make the right choice for your health.

What is quinine?

Quinine is a drug that has been used to treat muscle cramps since the 1930s. The prescription drug Qualaquin is approved by the FDA to treat malaria. However, it is often prescribed off-label (for unapproved purposes) for leg cramps.⁵

What are the risks of quinine?

Quinine has been found to have side effects that can be life-threatening. They include:⁷

• Thrombocytopenia (low levels of platelets in the blood, which help it clot)
• Hypersensitivity reactions (overreactions of the immune system)
• QT prolongation (when the heart muscle takes longer to recharge between heartbeats)

Less serious side effects of quinine include:⁸

• Cinchonism (a kind of poisoning that can include tinnitus, nausea, vomiting, photophobia, dysphoria, and dizziness)
• Hypoglycemia (low blood sugar)
• Hypotension (low blood pressure)
• Visual and hearing disturbances (including irreversible loss)
• Gastrointestinal symptoms
• Skin issues

Quinine can also interfere with other drugs. These include:⁷

• Antacids that contain aluminum
• Digoxin (Digox)
• Cimetidine (Tagamet)
• Warfarin (Coumadin)

Long-term use of quinine has also been tied to an increase in death. One study focused on people who consumed the equivalent of more than 1 liter of tonic water a day for at least a year. Quinine increased their risk of death by 3 times. The risk was highest in people under the age of 50.⁸

More research is needed to understand the link between increased risk of death and quinine. However, the risks of quinine – especially with long-term use – are proven.

What are more natural alternatives to treat RLS?

Drugs can help reduce symptoms of RLS. There are also some lifestyle and behavior changes that might help improve symptoms. These include:⁹

• Warm baths and massages to relax muscles
• Warm or cold packs to reduce sensations in the legs
• Reducing or cutting out caffeine, since this can make symptoms worse
• Exercising early in the day
• Getting enough sleep, since exhaustion can make symptoms worse

Things to consider

If your symptoms of RLS get worse or are very disturbing, talk with your doctor about what has worked and what hasn’t. You might need to try different medications or combinations of medications and lifestyle changes to find what works for you.