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Parkinson's Disease: Enzyme Inhibitors

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Monoamine oxidase (MAO) is one of the key enzymes responsible for the breakdown of dopamine in the brain. Inhibiting the action of MAO-B (a type of MAO) with products such as Eldepryl, Zelapar and Azilect can prevent the breakdown of dopamine. More dopamine then remains for sending messages in the brain.

Advantages and disadvantages of MAO-B inhibitors

Advantages	Disadvantages
Allows a reduction in the dose of levodopa	Serious interactions with certain antidepressant medications
Delays the onset of the more serious side effects of levodopa	Numerous side effects including gastrointestinal upset, flu-like symptoms, skin reactions, joint pain

Catechol-O-methyl transferase (COMT) is another enzyme that breaks down both dopamine and levodopa. Inhibitors of COMT such as Comtess or Tasmar are taken with each dose of levodopa/DDC inhibitor. This blocks the action of the enzymes on levodopa so that more levodopa can reach the brain.

They work within the body and have little effect on the levodopa actually in the brain. A single capsule containing levodopa + DDC inhibitor + COMT inhibitor (Stalevo) is now available.

Advantages and disadvantages of the COMT inhibitors

Advantages	Disadvantages
Allow a reduction in the levodopa dose	Must be taken with every levodopa dose
Prolongs period of mobility in patients with motor complications by 20% to 80%	Several interactions with other drugs due to mechanism of action
	Numerous side effects due to increased dopaminergic activity including sleep disorders and dyskinesias
	Fixed combination of Stalevo® reduces the ability to titrate individual components

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Glossary

Glossary entries within this article:

Agonist
- Chemical substance or drug that enhances or mimics the activity of a neurotransmitter, for example dopamine.
Antagonist
- Chemical substance or drug that reduces the activity of a neurotransmitter, for example dopamine.
Catechol-O-methyltransferase (COMT)
- Enzyme responsible for the metabolism of levodopa in the blood and brain.
Dopamine
- Neurotransmitter in the CNS. Dopamine deficiency is one of the major anomalies in Parkinson’s disease leading to the major symptoms such as bradykinesia, tremor, and rigidity.
Enzyme
- Protein that controls biochemical reactions in cells, for example metabolism of drugs
Levodopa
- Precursor that is metabolized to dopamine in the brain. It is in important drug in treatment of Parkinson’s disease.
Monoamine oxidase (MAO)
- Enzyme that metabolizes dopamine.

In the glossary you will find terms that we have provided with some extra-information.

glossary

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