Pharmacology of Levodopa in Parkinson's Disease

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What is the reason for taking levodopa on an empty stomach?

To reduce the risk of anorexia
To prevent the onset of motor fluctuations
To avoid interference with the transport of levodopa into the CNS (correct)
To minimize the risk of tachycardia

What is the primary reason why the therapeutic response to levodopa declines over time?

The blood-brain barrier prevents levodopa from entering the CNS
The drug effects are antagonized by dopamine receptors
Levodopa is metabolized by monoamine oxidase in the CNS
The number of neurons capable of converting levodopa to dopamine decreases (correct)

What is the effect of pyridoxine on levodopa therapy?

It has no effect on levodopa
It causes hypertension due to increased catecholamines
It enhances the effect of levodopa
It reduces the effect of levodopa (correct)

What is the mechanism of action of carbidopa in enhancing the effects of levodopa?

Inhibiting dopamine decarboxylase in peripheral tissues (C) Signup and view all the answers

What is the primary advantage of coadministering carbidopa with levodopa?

Reduced side effects due to decreased metabolism in peripheral tissues (D) Signup and view all the answers

What is the consequence of combining MAO inhibitors with levodopa?

Hypertensive crisis (B) Signup and view all the answers

What is the effect of levodopa on the heart?

It causes tachycardia (B) Signup and view all the answers

What is the fate of administered levodopa in the absence of carbidopa?

It is metabolized in peripheral tissues and GI tract, leading to undesirable side effects (B) Signup and view all the answers

What is the primary mechanism of action of levodopa in the treatment of Parkinson's disease?

Converting to dopamine in the CNS, which is then released from synaptic vesicles (C) Signup and view all the answers

What is the reason for the brownish color of saliva and urine in patients taking levodopa?

Due to the presence of melanin pigment (A) Signup and view all the answers

What is the primary reason for administering levodopa with carbidopa?

To inhibit the metabolism of dopamine in the periphery (A) Signup and view all the answers

What is the effect of levodopa on the iris?

Mydriasis (B) Signup and view all the answers

What is the primary reason why dopamine does not cross the blood-brain barrier?

It is unable to cross the blood-brain barrier due to its chemical structure (D) Signup and view all the answers

What is the result of the rapid absorption of levodopa from the small intestine?

Fluctuations in plasma concentration (D) Signup and view all the answers

What is the benefit of combining levodopa with carbidopa in the treatment of Parkinson's disease?

It decreases the dose of levodopa needed by four- to fivefold (D) Signup and view all the answers

What is the effect of peripheral dopamine formation on the body?

It causes nausea, vomiting, cardiac arrhythmias, and hypotension (D) Signup and view all the answers

What is the typical response of patients with Parkinson's disease to levodopa-carbidopa therapy?

A decline in response during the 3rd to 5th year of therapy (D) Signup and view all the answers

Why is gradual withdrawal from levodopa therapy necessary?

To prevent rebound symptoms (C) Signup and view all the answers