In treatment of parkinsonism, L-Dopa is combined with carbidopa mainly
Correct Answer: To make more of L-Dopa available to cross the blood brain barrier
Description: Ans. d. (To make more of L-Dopa available to cross the blood brain barrier) (Ref. KDT 6th/418.)# Carbidopa & Benserazide are peripheral Decarboxylase inhibitor.# When administrated with L-dopa, they increase peripheral half-life of L-dopa & make more of it available to cross blood brain barrier.LEVODOPA# Levodopa is rapidly absorbed from the small intestine, but its absorption depends on the rate of gastric emptying and the pH of the gastric contents.# Food will delay the appearance of levodopa in the plasma.# Plasma concentrations usually peak between 1 and 2 hours after an oral dose, and the plasma half-life is usually between 1 and 3 hours, although it varies considerably between individuals.# Unfortunately, only about 1-3% of administered levodopa actually enters the brain unaltered, the remainder being metabolized extracerebrally, predominantly by decarboxylation to dopamine, which does not penetrate the blood-brain barrier.# This means that levodopa must be given in large amounts when it is used alone.# However, when it is given in combination with a dopa decarboxylase inhibitor that does not penetrate the blood- brain barrier, the peripheral metabolism of levodopa is reduced, plasma levels of levodopa are higher, plasma half-life is longer, and more dopa is available for entry into the brain.# Indeed, concomitant administration of a peripheral dopa decarboxylase inhibitor may reduce the daily requirements of levodopa by approximately 75%.
Category:
Pharmacology
Get More
Subject Mock Tests
Practice with over 200,000 questions from various medical subjects and improve your knowledge.
Attempt a mock test nowMock Exam
Take an exam with 100 random questions selected from all subjects to test your knowledge.
Coming SoonGet More
Subject Mock Tests
Try practicing mock tests with over 200,000 questions from various medical subjects.
Attempt a mock test now