Parkinson’s disease is a progressive movement disorder caused by loss of dopamine-producing neurons in the brain. Cardinal features are tremor at rest, stiffness, slowness of movement and postural instability. Treatment aims to replace or mimic the missing dopamine, and to delay disability.

Levodopa (combined with carbidopa) remains the most effective treatment for symptoms. It is usually started early — older ‘reserve levodopa for late’ thinking has been retired. Dopamine agonists, MAO-B inhibitors and COMT inhibitors are used alone or with levodopa to smooth out symptoms.