fluoxetine
Meaning of fluoxetine: It stays in the body far longer than the rest of its class, which softens the effect of a missed dose and of stopping.
Definition of fluoxetine
Fluoxetine is an antidepressant of the selective serotonin reuptake inhibitor class, the first of that class to come into wide use. It blocks the transporter that clears serotonin from the gap between nerve cells, raising the amount available there. It is prescribed for depression, obsessive-compulsive disorder, bulimia nervosa, panic disorder and premenstrual dysphoric disorder.
What is it used for?
| Condition | Note |
|---|---|
| Major depression | The original use, in adults and in children above a certain age |
| Obsessive-compulsive disorder | Usually requires a higher dose and a longer trial |
| Bulimia nervosa | Reduces the frequency of binge eating and purging |
| Panic disorder | Started at a low dose, since early doses can briefly worsen anxiety |
| Premenstrual dysphoric disorder | Sometimes taken during part of the cycle only |
Selective here means selective for the serotonin transporter rather than acting broadly across many receptors, which is what separates this class from the older antidepressants it displaced.
Why does its long duration matter?
Fluoxetine is broken down into norfluoxetine, which is itself active and clears from the body slowly, so the drug remains present for weeks after the last tablet rather than days. Three practical consequences follow. A missed dose matters less than it does with shorter-acting medicines in the same class. Stopping produces fewer discontinuation symptoms, because the level falls gradually by itself. Against that, interactions persist after stopping, so a gap is required before starting certain other drugs, and any adverse effect takes longer to fade once the drug is withdrawn. The same property makes it a reasonable choice where taking a tablet at the same time every day is difficult.
What effects are known?
Nausea, headache, disturbed sleep, restlessness and reduced appetite are common early and often settle. Sexual effects, including reduced desire and delayed orgasm, are common and tend to persist while treatment continues. Combining it with other serotonergic drugs raises the risk of serotonin syndrome, with agitation, fever, tremor and a fast heartbeat. It also inhibits liver enzymes that clear a number of other medicines, so levels of those drugs can rise. Like every antidepressant it carries a warning about increased suicidal thinking in children and young adults during the first weeks, which is the reason for close review at the start rather than a reason the class is avoided.
Also known as
Used in a sentence
The psychiatrist prescribed fluoxetine for the patient's major depressive disorder.
Good to know
Fluoxetine has a notably long duration of action compared with other antidepressants in its class, so its effects, and any lingering effects after it is stopped, persist longer than with shorter-acting medicines.