Monoamine oxidase inhibitors (MAOIs) were the first type of antidepressant developed. They`reeffective, but have generally been replaced by antidepressants that are safer and cause fewer sideeffects. MAOIs generally require diet restrictions because they can cause dangerously high bloodpressure when taken with certain foods. In spite of side effects, these medications are still a goodoption for some people. In certain cases, they relieve depression when other treatments havefailed.How MAOIs workAntidepressants such as MAOIs ease depression by affecting chemicalmessengers (neurotransmitters) used to communicate between braincells. Most antidepressants work by changing the levels of one or more ofthese naturally occurring brain chemicals.The enzyme monoamine oxidase is involved in removing theneurotransmitters norepinephrine , serotonin and dopamine from thebrain. MAOIs prevent this from happening, which makes more of thesebrain chemicals available. This is thought to boost mood by improvingbrain cell communication. MAOIs also affect other neurotransmitters inthe brain and digestive system, causing side effects.