Quinine Questions

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Quinine has been used since the 1930s to treat muscle cramps, especially nighttime cramps, and more recently it has also been used for restless leg syndrome. In 2006 the FDA cautioned about using quinine for this off-label use because of efficacy and safety concerns. Despite the FDA warning, quinine is still used for muscle cramps. Quinine is also found in lemon bitters and tonic water and it gives both the sharp taste they are known for. Recently a study was performed in the United Kingdom to look at the safety of long-term quinine use.

The study looked at more than 175,000 individuals with an average age of 70 and followed them for almost six years. Of the study group there were almost 45,000 individuals who had long-term, daily exposure to quinine with an average daily dose of 203 mg (to put the dose into perspective, a liter of tonic water contains about 100 mg of quinine). Three unexposed people were selected for every one exposed person. The exposed persons had been taking quinine for as long as 25 years. The study found that the death rate of those with long-term quinine exposure was higher than the control group. They also found that the death rate was dose-dependent, meaning those with higher amounts of quinine ingestion had higher death rates. The highest death rate was in those taking 400mg or more a day.

In other words the study found that individuals taking 100mg or more of quinine daily had higher death rates than non-quinine users. The higher death rate was particularly pronounced in those under age 50. All of the quinine was prescribed for muscle cramps or restless leg syndrome. The study did not include tonic water drinkers. One possible explanation for the higher death rate associated with quinine was that the human body may convert quinine into its chemical cousin quinidine. Quinidine is an antiarrhythmic medication used to treat abnormal heart rhythms. Like most antiarrhythmic medications, quinidine may also act as a pro-arrhythmic, meaning that it may induce potentially fatal heart arrhythmias. This pro-arrhythmic effect is why most physicians use caution when treating abnormal heart rhythms with quinidine or its related medications.

Of course the study did have its limitations. Firstly the authors did not have access to the actual cause of death in the participants, so it cannot be ascertained whether or not quinine had a role in the person’s demise. Secondly, the average age of the participants was 70 and unfortunately everyone’s risk of death rises as we age. And lastly, they did not factor in disease states that the participants may have had. For example, a 70-year-old person with heart disease, diabetes and hypertension has a higher risk of death than a healthy 70-year-old.

So if you are a gin or vodka and tonic person, you might want to limit your tonic intake, just to be on the safe side. But fear not, other tasty cocktail alternatives are always available. If you would like more information on the FDA warning go to:


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By Peter Galvin, MD

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