Phenylhydrazine is an MAOI. MAOIs stands for monoamine oxidase inhibitors. They are antidepressant drugs that work by preventing the enzyme monoamine oxidase from metabolizing neurotransmitters. These neurotransmitters include serotonin, norepenephrine, and dopamine. Because these neurotransmitters are not metabolized, they remain in the brain and this helps elevate mood. It is also thought that the drug supports nerve cells within the brain from glutamate sensitivity. This prevents glutamate from stimulating areas of the brain that are responsible for depression and anxiety. There are two types of monoamine oxidase enzymes. There is MAO-A and MAO-B. These enzymes work by removing molecular segments from the neurotransmitters so that these neurotransmitters will become inactive and can be metabolized. Some of the side effects of the drug include tremors, arrhythmia, and seizures. The action of phenylhydrazine binding to the enzyme permanently deactivates the enzyme and is irreversible.