Phenelzine is classified as which type of antidepressant?

• A. SNRI
• B. SSRI
• C. MAOI
• D. TCA

Answer: (C)

Monoamine oxidase inhibitors work by blocking the enzyme that breaks down monoamines like serotonin, norepinephrine, and dopamine. Phenelzine prevents this breakdown, so these neurotransmitters accumulate in the brain and help improve mood. This mechanism is distinct from reuptake inhibitors (SSRIs, SNRIs, and TCAs), which raise neurotransmitter levels by stopping their reabsorption rather than preventing their breakdown. Because phenelzine inhibits the breakdown of multiple monoamines, it’s classified as a monoamine oxidase inhibitor. Remember, this class requires dietary restrictions to avoid hypertensive crises from tyramine and has significant drug interaction risks, which is why it’s reserved for certain treatment-resistant cases.