Which of the following is true regarding monoamine oxidase inhibitors (MAOIs)?

• A. They increase peripheral degradation of tyramine.
• B. They are effective mainly when other treatments have failed.
• C. They decrease synaptic concentrations of biogenic amines.
• D. They can cause increased metabolism of serotonin.

Answer: (B)

Monoamine oxidase inhibitors (MAOIs) are a class of antidepressants that inhibit the function of monoamine oxidase, an enzyme responsible for the breakdown of neurotransmitters such as serotonin, norepinephrine, and dopamine in the brain. By inhibiting this enzyme, MAOIs lead to increased levels of these biogenic amines in the synaptic cleft, which enhances mood and has antidepressant effects.

The correct statement pertaining to MAOIs is that they are effective mainly when other treatments have failed. This is because MAOIs are often considered a second-line treatment option for depression due to their dietary restrictions and potential side effects. Patients who do not respond to first-line treatments, such as selective serotonin reuptake inhibitors (SSRIs) or other conventional antidepressants, may be prescribed MAOIs to achieve better therapeutic outcomes.

The incorrect choices involve misunderstandings of how MAOIs function. They do not increase peripheral degradation of tyramine; rather, they inhibit its breakdown, which could lead to hypertensive crises if tyramine-rich foods are consumed. MAOIs do not decrease synaptic concentrations of biogenic amines but rather increase them by preventing their degradation. Lastly, they do not increase the metabolism of serotonin;