Like most of the time in medicine should first try to find the cause (eg. Origin due to a metabolic disease, a cardiovascular disorder) if it does not, you can:

1. Doing massage the cramp (see more good advice to treat cramps)
2. Use if cramps recur, muscle relaxants such as tizanidine or tetrazepam (Sirdalud ®). Warning it is prescription drugs that can cause drowsiness.
3. In case of frequent nocturnal cramps, your doctor may prescribe medicines containing quinine (eg in Switzerland sold as quinine, ex. Hänseler Chininii Sulphate Coated 250 mg), a drug against malaria that would have a positive for the disease.
4. If cramps occur regularly, also use preventive medicines.