Ketamine for the Treatment of Depression in Parkinson's Disease

Parallel-group, randomised, quadruple-blind RCT comparing six intravenous ketamine infusions (0.5 mg/kg over 40 minutes) with saline placebo in participants with Parkinson's disease and major depressive disorder. Primary outcome is reduction in depression severity.

A subset will undergo baseline and post-treatment PET (synaptic density) and fMRI (functional connectivity) to examine mechanistic effects and network reorganisation underlying ketamine's antidepressant effect in PD.