Norfluoxetine

Norfluoxetine is the primary active metabolite of the widely used antidepressant drug fluoxetine, which is sold under various brand names including Prozac. Norfluoxetine is formed by the hepatic metabolism of fluoxetine and contributes significantly to the therapeutic effects and pharmacokinetics of fluoxetine.

Chemistry

Norfluoxetine is a derivative of fluoxetine, differing primarily by the absence of a methyl group on the nitrogen atom of the side chain. It retains the trifluoromethyl group and the ether linkage characteristic of fluoxetine. The chemical structure of norfluoxetine allows it to be a potent and selective inhibitor of the serotonin reuptake transporter (SERT), which enhances serotonin levels in the brain and contributes to its antidepressant effects.

Pharmacology

Mechanism of Action

Norfluoxetine acts primarily as a selective serotonin reuptake inhibitor (SSRI). By blocking the reuptake of serotonin into presynaptic nerve terminals, it increases the level of serotonin available in the synaptic cleft, which is thought to contribute to its antidepressant effects.

Pharmacokinetics

Norfluoxetine has a longer half-life compared to its parent compound, fluoxetine, typically ranging from 7 to 15 days. This extended half-life contributes to the maintenance of steady-state levels of the drug in the bloodstream and is partly responsible for the delayed onset of therapeutic effects and prolonged duration of action after discontinuation of fluoxetine.

Clinical Use

Norfluoxetine, through its action as part of fluoxetine therapy, is used in the treatment of major depressive disorder, obsessive-compulsive disorder, bulimia nervosa, and panic disorder. It is also used off-label for other conditions, including various forms of anxiety and depressive syndromes.

Safety and Side Effects

The side effect profile of norfluoxetine is similar to that of fluoxetine and includes symptoms such as nausea, insomnia, and sexual dysfunction. Due to its long half-life, norfluoxetine may also contribute to the persistence of these side effects even after fluoxetine has been discontinued.

See Also

• Fluoxetine
• Selective serotonin reuptake inhibitor
• Antidepressant