MAOs, or monoamine oxidases, are enzymes that break down neurotransmitters and stop their messaging activity. MAO-A breaks down serotonin, epinephrine and norepinephrine; MAO-B deactivates dopamine.

With the wide variety of drugs available for depression and anxiety, it can be hard to know which drugs fall into which class, and what the accompanying effects are. Zoloft is not an MAO inhibitor but is a selective serotonin reuptake inhibitor (SSRI).