Mode of action of fluoxetine –
## **Core Concept**
Fluoxetine is an antidepressant medication that belongs to the class of selective serotonin reuptake inhibitors (SSRIs). It primarily acts on the neurotransmitter serotonin (5-HT) in the brain. The core concept being tested here is the mechanism of action of SSRIs.
## **Why the Correct Answer is Right**
The correct answer, , indicates that fluoxetine works by selectively inhibiting the reuptake of serotonin (5-HT) into the presynaptic neuron. This action increases the concentration of serotonin in the synaptic cleft, allowing more serotonin to interact with postsynaptic receptors. The increased serotonin levels help to improve mood and reduce symptoms of depression. The mechanism involves the inhibition of the serotonin transporter (SERT), which is responsible for the reuptake of serotonin.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because fluoxetine does not primarily act as a monoamine oxidase inhibitor (MAOI). MAOIs work by blocking the action of monoamine oxidase, an enzyme that breaks down monoamines such as serotonin, norepinephrine, and dopamine.
- **Option B:** This option is incorrect because fluoxetine does not primarily act by blocking alpha-2 adrenergic receptors. Alpha-2 adrenergic receptors are involved in the regulation of neurotransmitter release, but this is not the primary mechanism of action of fluoxetine.
- **Option D:** This option is incorrect because fluoxetine does not primarily act as a tricyclic antidepressant (TCA) by blocking norepinephrine and serotonin reuptake non-selectively. TCAs have a broader mechanism of action that includes blocking various receptors and reuptake transporters.
## **Clinical Pearl / High-Yield Fact**
A key clinical pearl to remember is that SSRIs, including fluoxetine, are often associated with a delay in their therapeutic effects, typically taking several weeks to show significant improvement in depressive symptoms. Additionally, they can have side effects such as sexual dysfunction, nausea, and increased risk of bleeding.
## **Correct Answer:** . Inhibits serotonin reuptake.