If simple treatments (leg stretching, addition of potassium and magnesium and vitamin D to diet, etc. don't work-

Quinine is recommended by some doctors, but has some bad side effects. My current doctor says No.
See this article from National Institute for Health-
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1463088/

Of course leg cramps may be a symptom of several conditions, a doctor should look for underlying causes if the simple solutions don't work.

Pickle Juice or brines that are rich in potassium actually were mnetioned by my doctor, but I said "No way," so the alternatives of sea salt (see contents list to see if K (potassium) is present), bananas, etc. were recommended.
Some tonic waters also contain potassium. (But not too much gin and tonic).

See this article from University of Maryland Medical Center-
http://www.umm.edu/patiented/articles/what_restless_legs_syndrome_other_sleep-related__leg_disorders_000095_1.htm
(or just google)

Magnesium is available in several compounds. Vitamin D (recommended by doctors in our Canadian area where sunlight is ineffective for much of the year) also should be in the diet.

And if simple solutions don't work, talk it over with your physician, and perhaps ask to see a specialist.
(Consultants are no problem in Canada, but sometimes long waits. All covered by the medical service.)