“I noticed at the health food store that tyrosine was available. If I recall my college biochemistry, tyrosine is the natural precursor to dopa. Why don’t doctors prescribe tyrosine supplements for Parkinson’s disease?”
Dr. Sanchez-Ramos said...
The amino acid tyrosine is indeed a natural precursor of dopamine. It requires two biochemical reactions to become active as dopamine. As you know, dopamine is the neurochemical which is deficient in the brain of PD patients. However, rather than increase consumption of tyrosine to try to replace the lacking dopamine, it is more efficient to use levo-dihydroxyphenylalanine (L-DOPA) which is the immediate biochemical intermediate in the production of dopamine. By consuming large amounts of DOPA (four to six grams per day) one can make up for the lack of dopamine and many of the symptoms of PD improve dramatically. By combining levodopa with another substance (carbidopa) that prevents L-DOPA’s breakdown in the liver, one can get by with much lesser amounts (300 -600 mg) of L-DOPA per day. The combination of L-DOPA/carbidopa is called Sinemet, the major therapy for the relief of signs and symptoms of PD. L-DOPA/carbidopa is available as a generic drug and is much less expensive than it used to be. If Sinemet improves your symptoms, then you must be careful about taking other amino acids (such as tyrosine, phenylalanine) since they may interfere with the absorption from the stomach and transport of levodopa from blood into the brain. The amino acid supplements found in health food stores should not be used when Sinemet or levodopa/carbidopa are being taken for relief of PD symptoms.