Dear Mr Raiyappa,
As time goes, patients with Parkinson's disease develop "on-off" phenomenon which means that the drug's efficacy and the total length of time that the medicines are effective becomes increasingly less. At the beginning of treatment, the medines must have been effective for 4-6 hours, but as time goes, its effectiveness becomes lesser and lesser. At this stage, treatments like deep brain stimulation
are effective in giving symptomatic relief. If you are interested, you can get in touch with me and I can give you more information on Deep Brain stimulation and assess you to see whethere this procedure will be suitable for you.
Hope this helps.