l-DOPA, also known as levodopa and l-3,4-dihydroxyphenylalanine, is an amino acid that is made and used as part of the normal biology of humans, as well as some animals and plants. Humans, as well as a portion of the other animals that utilize l-DOPA in their biology, make it via biosynthesis from the amino acid l-tyrosine.
Sinemet could cause severe side effects such as loss of balance and blackouts, according to a review by Simbidia at drugs.com
"I took it for two years and began to suffer all sorts of odd side effects which I didn't at first associate with the drug. But the worst was one that nearly killed me. I didn't even realize it was happening at first because I was having brief periods of blackout. I'd be walking and suddenly feel as though the earth had shifted under my feet. It finally happened while I was driving."