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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Atypical Antipsychotic [EPC]
Fluoxetine is a Selective Serotonin Reuptake Inhibitor (SSRI) and Atypical Antipsychotic [EPC] used to treat major depressive disorder, OCD, bulimia nervosa, and panic disorder. It works by increasing serotonin levels in the brain to improve mood and behavior.
Name
Fluoxetine
Raw Name
FLUOXETINE HYDROCHLORIDE
Category
Atypical Antipsychotic [EPC]
Salt Form
Hydrochloride
Drug Count
7
Variant Count
234
Last Verified
February 17, 2026
RxCUI
310384, 310385, 313989, 2532159, 2532163, 403969, 403970, 403971, 403972, 721787, 248642, 313990, 310386, 1190110, 104849, 205535, 261287, 313995
UNII
I9W7N6B1KJ, N7U69T4SZR, 01K63SUP8D
About Fluoxetine
Fluoxetine is a Selective Serotonin Reuptake Inhibitor (SSRI) and Atypical Antipsychotic [EPC] used to treat major depressive disorder, OCD, bulimia nervosa, and panic disorder. It works by increasing serotonin levels in the brain to improve mood and behavior.
Detailed information about Fluoxetine
This page is for informational purposes only and does not replace medical advice. Consult a qualified healthcare professional before using any medication containing Fluoxetine.
Fluoxetine, widely known by the brand name Prozac, is a landmark medication in the field of psychopharmacology. It belongs to a class of drugs known as Selective Serotonin Reuptake Inhibitors (SSRIs). Although the provided classification includes the term Atypical Antipsychotic [EPC], it is primarily and historically categorized as an SSRI. First approved by the U.S. Food and Drug Administration (FDA) in December 1987, Fluoxetine revolutionized the treatment of mental health conditions due to its favorable safety profile compared to older tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs).
As a therapeutic agent, Fluoxetine is indicated for the treatment of Major Depressive Disorder (MDD), Obsessive-Compulsive Disorder (OCD), Bulimia Nervosa, and Panic Disorder (with or without agoraphobia). It is also used in combination with olanzapine for the treatment of depressive episodes associated with Bipolar I Disorder and treatment-resistant depression. The medication is available as fluoxetine hydrochloride and is designed to modulate the neurochemical balance within the central nervous system (CNS).
The therapeutic efficacy of Fluoxetine is primarily attributed to its ability to inhibit the reuptake of serotonin (5-hydroxytryptamine or 5-HT) at the presynaptic neuronal membrane. In a healthy brain, serotonin is released into the synaptic cleft (the space between neurons) to transmit signals. Under normal conditions, much of this serotonin is reabsorbed by the releasing neuron through a transport protein. Fluoxetine binds to this serotonin transporter (SERT) with high affinity, effectively blocking the reabsorption process.
By preventing the 'reuptake' of serotonin, Fluoxetine increases the concentration of this neurotransmitter within the synaptic cleft. This sustained presence of serotonin leads to enhanced serotonergic neurotransmission, which is believed to alleviate symptoms of depression and anxiety. Beyond its primary SSRI activity, Fluoxetine also exhibits weak antagonism at the 5-HT2C receptor, which may contribute to its unique energizing effect compared to other SSRIs like paroxetine or sertraline. This 5-HT2C antagonism can lead to an increase in norepinephrine and dopamine levels in the prefrontal cortex, which may explain its utility in treating certain types of lethargic depression.
Understanding the pharmacokinetics of Fluoxetine is crucial for clinical management, particularly due to its exceptionally long half-life.
Fluoxetine is FDA-approved for several psychiatric conditions across different age groups:
Off-label uses, which your doctor may consider based on clinical evidence, include the treatment of Social Anxiety Disorder, Post-Traumatic Stress Disorder (PTSD), and Premature Ejaculation.
Fluoxetine is available in several formulations to accommodate different patient needs:
> Important: Only your healthcare provider can determine if Fluoxetine is right for your specific condition. This overview is for educational purposes and does not replace professional medical advice.
Dosage for Fluoxetine is highly individualized and depends on the condition being treated. Healthcare providers typically start with a low dose and gradually increase it to minimize side effects.
Fluoxetine is one of the few SSRIs approved for use in children.
Because Fluoxetine is extensively metabolized by the liver, significant renal impairment does not usually require a dose adjustment. However, for patients on dialysis, caution is advised as the drug is not easily removed from the blood.
Since the liver is the primary site of metabolism, patients with cirrhosis or other liver diseases should receive a lower dose or a less frequent dosing schedule (e.g., every other day instead of daily).
Older adults may be more sensitive to the effects of SSRIs. Healthcare providers may consider a slower titration and a lower maximum dose, particularly if the patient has concurrent medical conditions or is taking other medications.
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and resume your regular schedule. Do not take two doses at once to make up for a missed one. Due to the long half-life of Fluoxetine, missing a single dose rarely causes immediate symptoms, but consistency is key for therapeutic success.
Symptoms of a Fluoxetine overdose may include seizures, rapid heartbeat (tachycardia), nausea, vomiting, agitation, and extreme drowsiness. In severe cases, coma or cardiac arrest can occur. If an overdose is suspected, contact emergency services or the Poison Control Center immediately. There is no specific antidote for Fluoxetine; treatment is supportive and focused on maintaining vital functions.
> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or stop the medication without medical guidance, as this can lead to a return of symptoms or rare withdrawal effects.
Most side effects of Fluoxetine occur during the first few weeks of treatment and often diminish as the body adjusts to the medication. Common experiences include:
> Warning: Stop taking Fluoxetine and call your doctor immediately if you experience any of these serious conditions.
With prolonged use, some patients may experience 'emotional blunting,' where they feel less intense emotions (both positive and negative). Weight gain can also occur after the initial period of weight loss, as appetite returns or metabolic changes occur. Bone fractures have been associated with long-term SSRI use, possibly due to changes in bone mineral density.
Fluoxetine carries an FDA Black Box Warning regarding Suicidality in Children, Adolescents, and Young Adults. Clinical trials showed that antidepressants increased the risk of suicidal thinking and behavior in those under age 25 during the initial stages of treatment. This warning emphasizes the need for close monitoring by caregivers and clinicians for any changes in behavior, worsening of depression, or emergence of suicidal ideation. It is important to note that depression itself is a leading cause of suicide, and the risk-benefit ratio must be carefully weighed by a physician.
Report any unusual symptoms or persistent side effects to your healthcare provider to ensure your treatment plan remains safe and effective.
Fluoxetine is a potent psychoactive medication that requires careful monitoring. Patients should be aware that it may take 4 to 6 weeks (or longer) to feel the full therapeutic benefits. It is critical not to stop the medication abruptly, even if you feel better, as this can lead to a return of symptoms.
Suicidality and Antidepressant Drugs: Antidepressants increased the risk of suicidal thoughts and behavior in children, adolescents, and young adults (ages 18-24) in short-term studies. These studies did not show an increase in the risk of suicidal thoughts and behavior with antidepressant use in patients over age 24; there was a reduction in risk with antidepressant use in patients aged 65 and older. Patients of all ages who are started on antidepressant therapy should be monitored appropriately and observed closely for clinical worsening, suicidality, or unusual changes in behavior.
Healthcare providers may perform the following tests during treatment:
Fluoxetine may impair judgment, thinking, or motor skills. Do not drive or operate heavy machinery until you know how the medication affects you. While many find it stimulating, others experience significant drowsiness.
While Fluoxetine does not specifically increase the impairment caused by alcohol in clinical studies, it is strongly recommended to avoid alcohol. Alcohol can worsen depression and increase the risk of side effects like dizziness and drowsiness.
Although Fluoxetine's long half-life makes it less likely to cause 'discontinuation syndrome' compared to shorter-acting SSRIs (like Paxil), tapering is still recommended. Suddenly stopping can cause dizziness, sensory disturbances, and anxiety. Always follow a doctor-prescribed tapering schedule.
> Important: Discuss all your medical conditions, including heart problems, liver disease, or a history of seizures, with your healthcare provider before starting Fluoxetine.
Fluoxetine does not typically interfere with standard laboratory tests, but it may cause false-positive results in urine drug screens for amphetamines (depending on the specific assay used).
Mechanism of Interaction: Most interactions occur via Pharmacokinetic inhibition (Fluoxetine blocking the enzymes that break down other drugs) or Pharmacodynamic synergy (two drugs having the same effect, such as thinning the blood or raising serotonin).
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, including over-the-counter pain relievers.
Fluoxetine must NEVER be used in the following circumstances:
Conditions requiring a careful risk-benefit analysis by a physician:
While there is no direct cross-sensitivity between Fluoxetine and other classes of antidepressants (like TCAs), patients who have experienced severe 'activation' or 'mania' on one SSRI are likely to experience it on another. Patients with a history of sensitivity to other phenylpropylamine derivatives should be monitored closely.
> Important: Your healthcare provider will evaluate your complete medical history, including any history of heart rhythm problems or liver issues, before prescribing Fluoxetine.
Fluoxetine is classified as a drug that should only be used during pregnancy if the potential benefit justifies the potential risk to the fetus.
Fluoxetine and its metabolite norfluoxetine are excreted into breast milk. Concentrations in the infant's blood can be higher with Fluoxetine than with other SSRIs like sertraline. Reports of irritability, poor feeding, and slow weight gain have occurred in nursing infants. If a mother requires Fluoxetine, the infant should be closely monitored for these symptoms, or alternative antidepressants with lower milk excretion may be considered.
Fluoxetine is FDA-approved for MDD in children aged 8+ and OCD in children aged 7+. It is not approved for panic disorder or bulimia in children. Clinical trials have shown that Fluoxetine can cause a slight decrease in weight gain and height growth in pediatric patients. Growth should be monitored regularly during treatment.
Elderly patients are at a higher risk for Hyponatremia (low sodium) and Falls. SSRIs are listed in the Beers Criteria as medications to use with caution in the elderly. Age-related decreases in liver and kidney function may necessitate lower doses.
In patients with mild to moderate renal impairment, no dose adjustment is typically needed. However, in end-stage renal disease, Fluoxetine and norfluoxetine may accumulate over time. Use with caution.
Because the liver is the primary site for the metabolism of Fluoxetine to norfluoxetine, patients with liver disease (Child-Pugh Class A, B, or C) should receive a lower or less frequent dose. A common strategy is to dose every other day instead of daily.
> Important: Special populations require individualized medical assessment. Always inform your doctor if you are pregnant, planning to become pregnant, or breastfeeding.
Fluoxetine is a potent and selective inhibitor of the neuronal reuptake of serotonin (5-HT). It binds to the sodium-dependent serotonin transporter (SERT) on the presynaptic neuron. By inhibiting SERT, Fluoxetine prevents the clearance of serotonin from the synaptic cleft, thereby increasing the duration and intensity of serotonergic signaling at the postsynaptic receptors (5-HT1A, 5-HT2, etc.). Unlike tricyclic antidepressants, Fluoxetine has very low affinity for alpha-adrenergic, histamine, and muscarinic receptors, which accounts for its improved side effect profile.
Fluoxetine's primary effect is on the serotonergic system, but it also has secondary effects. It is a weak antagonist at the 5-HT2C receptor. Antagonism of 5-HT2C receptors leads to the disinhibition of norepinephrine and dopamine release in the prefrontal cortex, which may contribute to its antidepressant and pro-cognitive effects. The time to onset for mood improvement is typically 2 to 4 weeks, while the full effect on OCD or Bulimia may take 8 to 12 weeks.
| Parameter | Value |
|---|---|
| Bioavailability | >72% (Oral) |
| Protein Binding | 94.5% |
| Half-life (Parent) | 2 to 4 days |
| Half-life (Metabolite) | 7 to 15 days |
| Tmax | 6 to 8 hours |
| Metabolism | Hepatic (CYP2D6, CYP3A4) |
| Excretion | Renal (80%), Fecal (15%) |
Fluoxetine is classified as a Selective Serotonin Reuptake Inhibitor (SSRI). It is chemically unrelated to tricyclic, tetracyclic, or other available antidepressant agents. Related medications in the same class include Sertraline (Zoloft), Paroxetine (Paxil), Citalopram (Celexa), and Escitalopram (Lexapro).
Medications containing this ingredient
Common questions about Fluoxetine
Fluoxetine is primarily used to treat Major Depressive Disorder, Obsessive-Compulsive Disorder (OCD), Bulimia Nervosa, and Panic Disorder. It is also FDA-approved for the treatment of Premenstrual Dysphoric Disorder (PMDD) and, in combination with olanzapine, for bipolar depression and treatment-resistant depression. Healthcare providers may also prescribe it off-label for conditions like PTSD or social anxiety. It works by increasing the levels of serotonin in the brain, which helps regulate mood, sleep, and appetite. Because of its safety profile, it is one of the most commonly prescribed antidepressants worldwide.
The most common side effects include nausea, insomnia, nervousness, dry mouth, and excessive sweating. Many patients also report a decrease in appetite and initial weight loss during the first few weeks of therapy. Sexual side effects, such as decreased libido or delayed orgasm, are also relatively common and may persist throughout treatment. Most physical side effects like nausea and jitters tend to fade after the first two weeks as the body adjusts. If these symptoms are severe or do not go away, you should consult your healthcare provider for a possible dose adjustment.
It is generally recommended that you avoid alcohol while taking Fluoxetine. Although clinical studies have not shown that Fluoxetine significantly increases the intoxicating effects of alcohol, both substances affect the central nervous system. Alcohol is a depressant and can counteract the benefits of the medication, making your depression or anxiety symptoms worse. Additionally, the combination can increase side effects like dizziness, drowsiness, and impaired judgment. For the best therapeutic outcome, maintaining a lifestyle without alcohol is advised during treatment.
Fluoxetine use during pregnancy requires a careful discussion with your doctor regarding risks and benefits. There is a small potential risk of heart defects in the baby if taken during the first trimester, and a risk of Persistent Pulmonary Hypertension of the Newborn (PPHN) if taken during the third trimester. However, untreated depression also poses significant risks to both the mother and the developing fetus, including preterm birth and low birth weight. Many women continue taking Fluoxetine during pregnancy under close medical supervision. Decisions should be individualized based on the severity of the mother's condition.
Fluoxetine is not a fast-acting medication; it typically takes 2 to 4 weeks to notice an improvement in mood or sleep patterns. For conditions like OCD or Bulimia, it may take up to 8 to 12 weeks to see the full therapeutic benefit. It is important to continue taking the medication daily as prescribed, even if you do not feel better immediately. Some patients may feel a slight increase in energy or anxiety before their mood begins to lift. If you have not noticed any improvement after 6 weeks, your doctor may consider adjusting your dose.
You should never stop taking Fluoxetine suddenly without consulting your doctor. Although Fluoxetine has a very long half-life, which means it leaves your body slowly and is less likely to cause immediate withdrawal symptoms than other SSRIs, 'discontinuation syndrome' can still occur. Symptoms of stopping too quickly include dizziness, headache, irritability, and 'brain zaps' (sensory disturbances). Stopping abruptly can also cause a rapid return of your original depression or anxiety symptoms. Your doctor will provide a tapering schedule to gradually reduce your dose safely.
If you miss a dose of Fluoxetine, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and continue with your regular routine. Do not take two doses at once to make up for the one you missed. Because Fluoxetine stays in your system for a long time, missing one dose is unlikely to cause a significant setback in your treatment. If you miss several doses in a row, contact your healthcare provider for guidance on how to restart your regimen.
Fluoxetine is often associated with weight loss during the initial stages of treatment due to its potential to suppress appetite. However, over the long term (months to years), some patients may experience weight gain. This can be due to an improvement in mood leading to a better appetite, or changes in metabolism associated with chronic SSRI use. Compared to other antidepressants like mirtazapine or paroxetine, Fluoxetine is generally considered to be 'weight-neutral' or even associated with slight weight loss. Weight changes vary significantly from person to person.
Fluoxetine has several significant drug interactions, so it is vital to tell your doctor about everything you take. It should never be taken with MAOIs, thioridazine, or pimozide due to the risk of fatal heart rhythms or Serotonin Syndrome. It can also increase the risk of bleeding when taken with aspirin, NSAIDs, or blood thinners like warfarin. Because Fluoxetine inhibits the CYP2D6 enzyme, it can increase the levels of many other drugs in your system. Always check with a pharmacist or doctor before starting any new over-the-counter or prescription medication.
Yes, Fluoxetine is widely available as a generic medication, which is typically much less expensive than the brand-name version, Prozac. Generic Fluoxetine is FDA-approved and required to meet the same standards for safety, strength, and quality as the brand-name drug. It is available in various forms, including capsules, tablets, and oral solutions. Most insurance plans cover the generic version. If you have concerns about switching between brand and generic, discuss them with your pharmacist, though they are considered therapeutically equivalent.