Levodopa’s ability to reduce the distressing symptoms of early-stage Parkinson’s disease has earned itself enough street cred to become the first-line treatment for the condition. However, there’s a flip-side to every coin, and this drug is no exception.

Researchers at Columbia University in New York tested the drug on 361 patients with early Parkinson’s and, as expected, found that levodopa helped to alleviate the stiffness, tremors, spasms and poor muscle control associated with the neurodegenerative disorder.

However, on scanning the patients’ brains, they discovered that the drug was actually causing damage to nerve endings - in particular, to the dopamine receptors that play an important role in controlling symptoms.

In other words, while patients need the drug to ease symptoms, they are also accelerating the progress of the disease. So far, this paradox has left scientists stumped, with a big question mark hanging over how the long-term use of levodopa will affect patients with Parkinson’s (N Engl J Med, 2004; 351: 2547-9).

Another drug under the microscope is rivastigmine, usually prescribed for people with Alzheimer’s. A research team in Istanbul decided to try it for mild-to-moderate dementia related to advanced Parkinson’s. While 19.8 per cent of patients improved in symptoms, 13 per cent got worse. To top it off, 29 per cent reported nausea, 17 per cent suffered vomiting and 10 per cent had tremors (N Engl J Med, 2004; 351: 2509-18).