What causes serotonin syndrome?

Serotonin syndrome is a potentially life-threatening condition resulting from an excess of serotonin in the central nervous system. The correct answer highlights a particularly dangerous combination of medications: the concurrent use of selective serotonin reuptake inhibitors (SSRIs) and monoamine oxidase inhibitors (MAOIs). This combination is problematic because both drug classes increase serotonin levels, leading to excessive serotonergic activity.

When SSRIs block the reuptake of serotonin at the synapse, they allow more serotonin to remain available for receptor binding. Meanwhile, MAOIs inhibit the enzyme responsible for breaking down serotonin, further contributing to increased serotonin levels. The combination of these mechanisms can quickly lead to overwhelming serotonin levels and the onset of serotonin syndrome, characterized by symptoms such as agitation, confusion, rapid heart rate, and potentially severe complications like hyperthermia and seizures.

The other options, while related to serotonin levels, do not directly tie in with the mechanism that most commonly precipitates serotonin syndrome. For example, an SSRI overdose may lead to significant side effects, but the concurrent use of SSRIs and MAOIs represents the highest risk for causing this syndrome due to their synergistic effects on serotonin. Stopping a medication suddenly can cause withdrawal symptoms or a rebound effect, and