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Nocturnal leg cramps are involuntary muscle contractions that occur in the calves, soles of the feet, or other muscles in the body during the night or (less commonly) while resting. The duration of nocturnal leg cramps is variable, with cramps lasting anywhere from a few seconds to several minutes. Muscle soreness may remain after the cramp itself ends. These cramps are more common in older people. They happen quite frequently in teenagers and in some people while exercising at night. The precise cause of these cramps is unclear. Potential contributing factors include dehydration, low levels of certain minerals (magnesium, potassium, calcium, and sodium, although the evidence has been mixed), and reduced blood flow through muscles attendant in prolonged sitting or lying down. Nocturnal leg cramps (almost exclusively calf cramps) are considered “normal” during the late stages of pregnancy. They can, however, vary in intensity from mild to extremely painful.
A lactic acid buildup around muscles can trigger cramps; however, these happen during anaerobic respiration when a person is exercising or engaging in an activity where the heartbeat speeds up. Medical conditions associated with leg cramps are cardiovascular disease, hemodialysis, cirrhosis, pregnancy, and lumbar canal stenosis. Differential diagnoses include restless legs syndrome, claudication, myositis, peripheral neuropathy. All of these can be differentiated through careful history and physical examination.
Gentle stretching and massage, putting some pressure on the affected leg by walking or standing, or taking a warm bath or shower may help to end the cramp. If the cramp is in the calf muscle, pulling the big toe gently backwards will stretch the muscle and, in some cases, cause almost immediate relief. There is limited evidence supporting the use of magnesium, calcium channel blockers, carisoprodol, and vitamin B12.
Quinine is no longer recommended for treatment of nocturnal leg cramps due to potential fatal hypersensitivity reactions and thrombocytopenia. Arrhythmias, cinchonism, hemolytic uremic syndrome can also occur at higher dosages.