Q. Can quinine relieve leg cramps?

A. You are sleeping peacefully when a sudden pain pierces your leg and jolts you awake. Nighttime leg cramps are often caused by involuntary contraction of the calf muscles while you sleep. They become more common with age.

Several studies have shown that people who regularly suffered nighttime leg cramps experienced fewer symptoms after taking quinine compared to a placebo. Most studies used a therapeutic dose of 200-300 milligrams quinine.

Quinine is the ingredient that produces the bitter flavor in tonic water. Tonic water, however, is unlikely to be effective against leg cramps because it contains too little quinine. To get a therapeutic dose of quinine from tonic water, you'd need to drink about a gallon in 24 hours!

Although many people do fine with quinine, for some it is extremely dangerous. Between 1969 and 2006, the Food and Drug Administration received 665 reports of serious adverse effects including 93 deaths. Complaints included severe allergic reactions, irregular heartbeats and liver damage. It also can cause birth defects and miscarriages. Quinine has a narrow margin between effective and toxic doses.

In 1995, the FDA banned over-the-counter marketing of quinine for leg cramps, however a scan of the Internet shows many companies still marketing products containing quinine. Many of these products list cinchona, a natural form of quinine, on their labels. It's unclear how much quinine these products contain. They are sold as "dietary supplements," while prescription-strength quinine is considered a drug. Dietary supplements are not as strictly regulated as medications.

Since 2007, the FDA has recommended that prescription-strength quinine be prescribed only for treatment of malaria. Malaria is life-threatening, so the benefits outweigh the risks. FDA noted that since leg cramps are not life-threatening, prescribing quinine for this condition is too risky.

If you are prone to leg cramps, it may be better to do stretching exercises such as wall pushups before bed. Applying a heating pad for 10 minutes every night may also help. When experiencing a leg cramp, try stretching by grasping your toes and gently pulling your foot toward you.

Sometimes dehydration or potassium deficiencies may be involved, especially in athletes or elderly people. If this is the case, drinking fluids and eating food sources of potassium may help. These include bananas, soybeans, cantaloupe, mangoes, potatoes and oranges.