From the FDA Drug Label
MAOs are currently subclassified into two types, A and B, which differ in their substrate specificity and tissue distribution. The naming conventions for monamine oxidases are MAO-A and MAO-B, which refer to the two types of monoamine oxidase enzymes that differ in their substrate specificity and tissue distribution 1.
- MAO-A is found predominantly in the intestinal tract and is involved in the catabolism of exogenous amines.
- MAO-B is found primarily in the brain and is involved in the catabolism of catecholamines and serotonin.
From the Research
Monoamine oxidase (MAO) inhibitors are named based on their selectivity for the two main isoforms of the enzyme: MAO-A and MAO-B, with the most recent and highest quality study 2 supporting the naming convention that includes the prefix "sel" for selective inhibitors, followed by "-giline" for irreversible inhibitors or "-line" for reversible inhibitors. The naming convention for MAO inhibitors is crucial for clinicians to quickly identify the selectivity and mechanism of action of these medications.
- The prefix "sel" is used for selective inhibitors,
- "-giline" is used for irreversible inhibitors,
- and "-line" is used for reversible inhibitors. For example, selegiline is a selective irreversible MAO-B inhibitor, while rasagiline follows the same pattern. Reversible inhibitors of MAO-A are often named with the suffix "-line," as in moclobemide. Non-selective MAO inhibitors that inhibit both isoforms typically have more varied naming patterns, such as phenelzine, tranylcypromine, and isocarboxazid, as noted in 3 and 4. These older, non-selective agents don't follow a consistent naming convention as they were developed before the distinction between MAO subtypes was well understood, as discussed in 5 and 6. The naming system helps clinicians quickly identify the selectivity and mechanism of action of these medications, which is important because MAO-A inhibitors carry dietary restrictions due to the risk of hypertensive crisis when combined with tyramine-rich foods, while selective MAO-B inhibitors at therapeutic doses generally don't require such restrictions, as highlighted in 2.
The most recent study 2 provides a comprehensive review of MAOs and their role in neurotransmitter metabolism, which supports the importance of understanding the naming convention for MAO inhibitors.
- The study notes that MAO A and B are mammalian flavoenzymes bound to the outer mitochondrial membrane,
- and that they have been the subject of many biochemical, structural, and pharmacological investigations due to their central role in neurotransmitter metabolism. The study also discusses the use of selective MAO B inhibitors, such as rasagiline and safinamide, in the treatment of Parkinson's disease, and highlights the potential neuroprotective effects of MAO inhibition. Overall, the naming convention for MAO inhibitors is an important aspect of their use in clinical practice, and is supported by the most recent and highest quality evidence 2.