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Monoamine Oxidase B Inhibitors

Selegiline

Selegilineis an inhibitor of the enzyme MAO-B (monoamine oxidase B). MAO-B breaks down dopamine. When it is inhibited, the action of dopamine is prolonged in the brain, and the symptoms of Parkinson's disease are improved. MAO-B inhibitors also have a mild antidepressant effect. Early studies of selegiline suggested that it may delay the progression of Parkinson's disease but this appears to have been confounded by a mild symptomatic effect. Currently there is no firm evidence that selegiline slows disease progression. It is effective as monotherapy for symptomatic relief or as an adjunctive agent.

Selegiline preparations include:

  • Eldepryl®: 5 mg capsule usually taken twice daily (morning and noon)
  • Atapryl®:   5 mg tablets usually taken twice daily (morning and noon)
  • Carbex®:   5 mg tablets usually taken twice daily (morning and noon)
  • Zelapar (an orally disintegrating form of selegiline): 1.25 mg tablets taken once daily (morning).

Side effects include heartburn, nausea, dry mouth, insomnia and dizziness. Confusion, nightmares, hallucinations, and headache occur less frequently.

Rasagiline

Rasagiline is another MAO-B inhibitor that has been approved for monotherapy and adjunct therapy in Parkinson’s disease. It is taken once daily and is less likely to cause insomnia than selegiline.   A recent study showed that treatment with 1 mg rasagiline provided benefits that were consistent with a possible disease-modifying (or neuroprotective) effect whereas treatment with 2 mg daily did not (Olanow et al, 2009)

Preparations:

  • Rasagiline (Azilect®) is available as 0.5 and 1 mg tablets, usually taken once daily

Side effects include abnormal movements and hallucinations (when taken with levodopa), headache, and fatigue.

Precautions when using MAO-B inhibitors

Meperidine (Demerol®) and tramadol are contraindicated. Dextromethorphan and ephedrine should also be avoided, as should over-the-counter cold remedies. Treatment with ciprofloxacin may increase the blood level of rasagiline and so concomitant use should be avoided.