Up to 56% of l-dopa fails to reach the brain

The effectiveness of L-dopa, a common medication for Parkinson's disease, varies greatly between patients due to differences in their gut bacteria. Normally, L-dopa needs to reach the brain to be converted into dopamine, which helps manage Parkinson's symptoms. However, certain gut bacteria can break down L-dopa before it gets to the brain, making the treatment less effective. Researchers found that specific bacteria, Enterococcus faecalis and Eggerthella lenta, are responsible for this breakdown. These bacteria use enzymes to convert L-dopa into a substance called m-tyramine, which is useless for treating Parkinson's. An existing drug, carbidopa, is supposed to prevent L-dopa from being broken down before it reaches the brain, but it doesn't work well against these gut bacteria. To counter this, the researchers identified another compound, (S)-α-fluoromethyltyrosine (AFMT), that can block the bacterial enzymes from breaking down L-dopa, improving its effectiveness. This discovery could lead to better treatments for Parkinson's by considering both the patient's gut bacteria and the medication itself.