I have to take Botox injections in my calf muscles every 12 weeks for leg cramps and freezing gait. The injections last about 8 weeks, then the leg cramps return. It is important to note that exercise is a must for PD and the more you exercise the muscles that are injected with Botox the faster the Botox leaves your body! The freezing gait has slightly improved.
I also get the injections in the bottom of both feet because of peripheral neuropathy. These are painful but I believe they are worth it.