MAO-B inhibitors

MAO-B inhibitors irreversibly block monoamine oxidase type B, the main form of the enzyme in the human brain, where it breaks down dopamine. With less breakdown, more dopamine stays in the striatum, easing Parkinson's symptoms and cutting 'off' time on levodopa. At licensed doses they spare MAO-A, which clears dietary tyramine in the gut, but this selectivity fades as the dose rises.

• SelegilineUnlike rasagiline it is metabolized to amphetamine and methamphetamine, and as a skin patch it is also licensed for major depression.
• RasagilineAt its licensed dose it is selective enough that tyramine limits are not usually needed, though foods with very large amounts are avoided.

• Early Parkinson's disease, on its own
• Add-on to levodopa to cut 'off' time
• Major depression (selegiline skin patch)

• Serotonin syndrome with pethidine or antidepressantsKnown forSerious
• Nausea
• Headache
• Dizziness on standing (orthostatic hypotension)
• More dyskinesia when taken with levodopa
• Hallucinations and confusionSerious
• Blood pressure surges with very tyramine-rich foodSerious
• Daytime sleepiness and sudden sleepSerious
• Compulsive gambling or spendingSerious
• Dry mouth

What the class has in common. Each drug's card has its own, and Known for marks what an exam expects you to know.

• Pethidine, tramadol, methadone, St John's wort and other MAO inhibitors are contraindicated: they risk serotonin syndrome.
• SSRIs, SNRIs and tricyclics can also trigger serotonin syndrome; fluoxetine needs a 5-week gap before starting.
• Above licensed doses MAO-A is blocked too, and tyramine-rich foods can cause a hypertensive crisis.
• Decongestants such as ephedrine and pseudoephedrine can raise blood pressure sharply.

Written for biofideX in plain words, after checking these references:

• Selegiline hydrochloride tablets: label (DailyMed)
• Rasagiline tablets: label (DailyMed)
• Rasagiline: product information (EMA)
• Selegiline hydrochloride (NCI Thesaurus)

For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.