All of the following are true regarding levodopa except
Dopamine does not cross the blood-brain barrier (BBB), so clinical trials were initiated with levodopa, the precursor of dopamine. Studies over the course of the next decade confirmed the value of levodopa and revolutionized the treatment of PD. Levodopa is routinely administered in combination with a peripheral decarboxylase inhibitor to prevent its peripheral metabolism to dopamine and the development of nausea, vomiting, and ohostatic hypotension due to activation of dopamine receptors in the area postrema that are not protected by the BBB. Levodopa-induced motor complications consist of fluctuations in motor response and involuntary movements known as dyskinesias which typically complicate "on" periods. When patients initially take levodopa, benefits are long-lasting (many hours) even though the drug has a relatively sho half-life (60-90 min). With continued treatment, however, the duration of benefit following an individual dose becomes progressively shoer until it approaches the half-life of the drug. This loss of benefit is known as the wearing-off effect Ref harrison 20th edition page 3126
Half life of levodopa is 60 to 90 minutes
Levodopa can cause ohostatic hypotension, dyskinesias
Levodopa cannot cross the blood brain barrier
With continued use, the duration of benefit following an individual dose of levodopa becomes progressively shoer.
C.N.S