The second most common complaint of patients with chronic kidney failure is muscle cramps. Typically these cramps involve the calf muscles, but they can occur in any muscle group. Involuntary contraction of the involved muscle(s) occurs, often at night, and may be quite painful. Some patients never develop muscle cramps. This complaint isn't quite as nonspecific as fatigue, but certainly does occur in healthy individuals, particularly following strenuous use of a muscle that isn't called upon often.
Again, doctors do not know what causes muscle cramps in patients with kidney disease. Potassium depletion also can cause muscle cramps, and patients who require potassium supplements (see Chapter 12) often note that omitting these supplements makes cramps worse. But potassium depletion is not the cause of muscle cramps in most kidney patients. Salt depletion also can cause muscle cramps, but this is rarely the cause in patients with kidney disease.
For unknown reasons, dietary treatment regularly reduces or eliminates muscle cramps. Also, cramps often can be relieved by quinine sulfate (available without a prescription). A dose of 300 mg or less, either when cramps occur or as a preventive, for example, at bedtime, often helps. Quinine is far from safe. In substantial dosage, it can cause allergic reactions that deplete elements of the blood, with disastrous consequences. For example, a 64-year-old man recently developed a life-threatening bleeding disorder after taking 2 to 5 large bottles of tonic containing quinine daily for 2 to 3 weeks to ward off muscle cramps.
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