Blockers and Inhibitors

These types of drugs block or inhibit the breakdown of levodopa or dopamine which in turn helps maintain dopamine levels in the motor neurons

Catecholamine-O-Methyltransferase (COMT) Inhibitor
COMT breaks down levodopa in the bloodstream reducing the amount that is able to cross the blood brain barrier to become available for conversion into dopamine in the brain. This class of drug blocks the action of the COMT enzyme which in turn maintains a higher level of L-dopa resulting in an increased the amount of dopamine (similar to action of carbidopa).

There are two types of COMT Inhibitors used in Parkinson's disease

  • Entacapone cannot cross the blood-brain barrier, and only works peripherally
  • Tolcapone can cross the blood brain barrier and prevents the breakdown of both dopamine and L-dopa by COMT enzymes in both the central and peripheral nervous system

Both must be taken with taken with levodopa in order for it to work

  • Entacapone (Comtan®)

Comtan®200 mg

  • Carbidopa/Levodopa + Entacapone (Stalevo®)

Stalevo®12.5/50/200 mg
Stalevo®25/100/200 mg
Stalevo®25/150/200 mg

  • Tolcapone (Tasmar®)

Tasmar® 100 mg
Tasmar® 200 mg

Monoamine Oxidase B (MOAB) Inhibitors
When released dopamine is not used (bound) in the transmission of the message, it can be taken back up into the releasing neuron. Monoamine Oxidase (MOA)is an enzyme that breaks down dopamine in the neuron (outside of the storage vesicles) to keep dopamine levels in the storage vesicles from over capacity. MAO-B (B is the type of receptor) inhibitors, bind to and inhibit the MAOB enzyme from breaking down dopamine. Prolonged use may enhance release of dopamine. MAOB Inhibitors can be taken alone (mono- therapy) or in combination with medications containing levodopa (adjunctive therapy).

  • Rasagiline (Azilect®) Azilect®1.0 mg, Azilect®.05 mg
  • Selegiline (Eldepryl®) Eldepryl®100 mg
  • Selegiline HCL Orally disintegrating (Zelepar®) Zelepar®1.25 mg

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