Ketamine is an FDA-approved drug with a known safety profile. Low-dose subanesthetic intravenous ketamine infusion treatment has led to long-term reduction of treatment-resistant depression and of chronic pain states. We report on low-dose subanesthetic intravenous ketamine infusion treatment in Parkinson's disease (PD) patients by 5 case studies and show a long-lasting therapeutic benefit to reduce l-DOPA-induced dyskinesia (LID), improve on time, and reduce depression. Based on the literature we hypothesize that low-dose ketamine may act as a 'chemical deep brain stimulation', by desynchronizing hypersynchronous oscillatory brain activity, including in the basal ganglia and the motor cortex. The presented PD case reports indicate tolerability, safety and long-term beneficial effects of low-dose ketamine infusion that should be further investigated in a properly controlled prospective clinical trial for treatment of LID, as well as the prevalent nonmotor features pain and depression in PD patients.