Idiopathic Muscle Cramps

These cramps, without significant muscle weakness, frequently occur in healthy middle-aged and elderly patients. They may develop at rest or with minor exercise. Typically, they occur at night during sleep and affect the calf or foot muscles, causing forceful plantar flexion of the foot or toes. Diagnosis is based on the history and lack of physical signs or disability.

Prevention and Treatment

Avoiding caffeine and other sympathetic stimulants may be helpful. Stretching the affected muscles for several minutes before sleep is often an effective preventive measure. Stretching immediately after the cramps occur usually relieves them (see Figure 54-1). Such exercises improve muscle and tendon flexibility and can reduce the motor unit activity in the stretched muscles.

Stretching is almost always preferable to empiric drug treatment. For example, quinine sulfate 200 to 300 mg at bedtime is not effective for night cramps and can cause a bitter taste, tinnitus, flushing, pruritus, and gastrointestinal disturbances, and it interacts with many other drugs. Calcium supplements (eg, calcium gluconate 1 to 2 g bid) are well tolerated, but their effectiveness is doubtful. Drugs used concomitantly with quinine and calcium include diphenhydramine 50 to 100 mg at bedtime, magnesium carbonate 250 to 500 mg bid, and low-dose benzodiazepines. However, the toxic effects of these drugs are likely to outweigh any benefit. Mexiletine 150 mg tid is sometimes effective when increased irritability of the lower motor neuron is suspected.