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[Pharmacology](https://durgical.com/en/pharmacology/) · Class

# MAO-B inhibitors

Drugs that slow the breakdown of dopamine in the brain. Modest benefit in Parkinson disease; watch for serotonergic and pressor drug interactions.

Updated 2026-11-01

## What they are

Selegiline and rasagiline inhibit monoamine oxidase B irreversibly; safinamide inhibits it reversibly. They are used alone in early Parkinson disease or added to levodopa to shorten «off» time.

## Mechanism of action

MAO-B is the main enzyme that oxidizes dopamine in the human striatum. Blocking it leaves more dopamine in the synapse. At usual doses they spare MAO-A in the gut and liver, so the dangerous tyramine «cheese reaction» of nonselective MAO inhibitors is much less likely, but selectivity is lost at higher doses.

Target: Monoamine oxidase B (MAO-B)

## Key points

- Contraindicated with meperidine, tramadol, methadone, dextromethorphan, St John's wort, cyclobenzaprine and other MAO inhibitors: risk of serotonin syndrome.
- Antidepressants (SSRIs, SNRIs, tricyclics) can also cause serotonin syndrome with them; combination needs close monitoring.
- Tyramine: usual doses do not require a strict diet, but foods with very large amounts of tyramine (aged cheeses, cured meats) can still raise blood pressure sharply.
- Selegiline is metabolized to amphetamine and methamphetamine (insomnia, anxiety); rasagiline is not.
- Added to levodopa they can increase dyskinesias, hallucinations and orthostatic hypotension.

## Drugs in this class

- [**Rasagiline** An irreversible, selective MAO-B inhibitor for Parkinson disease, alone or with levodopa. No amphetamine metabolites… Monoamine oxidase B (MAO-B)](https://durgical.com/en/pharmacology/rasagiline/)
- [**Selegiline** An irreversible MAO-B inhibitor for Parkinson disease. It forms amphetamine metabolites and has serious interactions… Monoamine oxidase B (MAO-B)](https://durgical.com/en/pharmacology/selegiline/)
- [**Safinamide** A reversible MAO-B inhibitor added to levodopa for «off» episodes. It also reduces glutamate release; same interaction… Monoamine oxidase B (MAO-B)](https://durgical.com/en/pharmacology/safinamide/)

## Test yourself

Think of the answer, then tap the question to see it.

## Which opioid is classically contraindicated with MAO-B inhibitors, and why?

Meperidine: the combination can cause stupor, rigidity, agitation and hyperthermia (serotonin toxicity).

## Why do MAO-B inhibitors rarely cause the cheese reaction at usual doses?

Gut and liver MAO-A, which destroys dietary tyramine, stays active; selectivity is lost at higher doses.

## Which MAO-B inhibitor produces amphetamine metabolites?

Selegiline (L-amphetamine and L-methamphetamine), which can cause insomnia and anxiety.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 21 (McGraw Hill, 2023); [DailyMed - RASAGILINE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e802c83c-e581-4a11-b83d-1df47120078d) (DailyMed (U.S. National Library of Medicine), 2026); [DailyMed - SELEGILINE HYDROCHLORIDE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=2aa9f8ee-6a86-6cf1-bec7-6a1ffa5e1ae2) (DailyMed (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=N04BD) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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