Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) widely prescribed for the management of major depressive disorder, obsessive-compulsive disorder, panic disorder, and bulimia nervosa. As a first-line pharmacological intervention, it functions by increasing extracellular serotonin levels in the central nervous system, thereby improving mood, reducing anxiety, and stabilizing emotional regulation. Its well-established efficacy, favorable safety profile, and once-daily dosing convenience make it a cornerstone in modern psychiatric treatment protocols.

Features

• Active ingredient: Fluoxetine hydrochloride
• Available in 10 mg, 20 mg, and 40 mg oral capsules, plus liquid formulation
• Selective inhibition of serotonin reuptake pumps (SERT)
• FDA-approved for multiple psychiatric and eating disorders
• Proven bioavailability of approximately 72–90% with linear kinetics
• Half-life of 1–3 days (4–6 days for active metabolite norfluoxetine)

Benefits

• Achieves significant reduction in symptoms of depression and anxiety
• Helps restore normal sleep, appetite, and energy levels
• Reduces frequency and intensity of obsessive thoughts and compulsive behaviors
• Supports long-term mood stabilization with once-daily dosing
• Lower risk of cardiotoxicity and anticholinergic effects compared to older antidepressants
• Non-sedating profile supports daytime functionality

Common use

Fluoxetine is indicated for the treatment of major depressive disorder (MDD) in adults and pediatric patients aged 8 years and older. It is also approved for obsessive-compulsive disorder (OCD), panic disorder with or without agoraphobia, and bulimia nervosa as part of a comprehensive treatment plan. Off-label uses include premenstrual dysphoric disorder (PMDD), post-traumatic stress disorder (PTSD), and certain forms of chronic pain. Treatment response is typically observed within 2–4 weeks, with full therapeutic effects manifesting after 4–6 weeks of consistent use.

Dosage and direction

Initial dosing for depression in adults is typically 20 mg once daily in the morning, with possible titration to a maximum of 80 mg/day based on clinical response and tolerability. For OCD, dosing may start at 20 mg/day and increase gradually. Pediatric dosing for MDD (ages 8–18) starts at 10 mg/day. Administration with food may minimize potential gastrointestinal upset. Dose adjustments are necessary in patients with hepatic impairment or those taking concomitant medications that inhibit CYP2D6. Abrupt discontinuation should be avoided; a gradual taper is recommended to minimize withdrawal symptoms.

Precautions

Patients should be monitored for emergence of anxiety, agitation, panic attacks, insomnia, irritability, hostility, impulsivity, and hypomania, particularly during initial treatment or dose adjustments. Use with caution in individuals with a history of seizures, bipolar disorder, or angle-closure glaucoma. Fluoxetine may impair judgment, thinking, or motor skills; patients should avoid driving or operating machinery until they know how the medication affects them. Regular assessment of renal and hepatic function is advised during long-term therapy.

Contraindications

Fluoxetine is contraindicated in patients taking monoamine oxidase inhibitors (MAOIs) or within 14 days of discontinuing MAOI therapy due to risk of serotonin syndrome. It is also contraindicated in patients with known hypersensitivity to fluoxetine or any component of the formulation. Use is not recommended in patients with uncontrolled narrow-angle glaucoma or severe hepatic impairment. Concomitant use with pimozide or thioridazine is contraindicated due to risk of QT prolongation.

Possible side effect

Common side effects include headache, nausea, diarrhea, dry mouth, sweating, anxiety, nervousness, insomnia, drowsiness, and decreased libido. Sexual dysfunction such as anorgasmia or delayed ejaculation may occur. Less frequently, rash, itching, weight changes, and hyponatremia (especially in elderly patients) have been reported. Rare but serious adverse effects include serotonin syndrome, abnormal bleeding, seizures, angle-closure glaucoma, and manic episodes. Most side effects are dose-dependent and may diminish over time.

Drug interaction

Fluoxetine is a strong inhibitor of CYP2D6 and a moderate inhibitor of CYP3A4, which may increase plasma levels of drugs metabolized by these enzymes (e.g., tricyclic antidepressants, antipsychotics, beta-blockers, certain opioids). Concomitant use with other serotonergic drugs (tramadol, triptans, linezolid) increases risk of serotonin syndrome. NSAIDs, aspirin, or other anticoagulants may increase bleeding risk. Use with drugs that prolong QT interval (e.g., antipsychotics, antiarrhythmics) requires careful monitoring. Avoid combining with MAOIs.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is close to the time of the next scheduled dose. In that case, the missed dose should be skipped and the regular dosing schedule resumed. Doubling up on doses is not recommended. Patients should contact their healthcare provider if multiple doses are missed or if they are uncertain how to proceed.

Overdose

Symptoms of overdose may include nausea, vomiting, agitation, restlessness, hypomania, seizures, and cardiovascular effects such as tachycardia. Fatalities have been reported in combination with other drugs. There is no specific antidote; management includes supportive care, gastric lavage if presented early, activated charcoal, and monitoring of vital signs. ECG monitoring is recommended due to potential QT prolongation.

Storage

Store at room temperature (20–25°C or 68–77°F) in a tightly closed container, protected from light and moisture. Keep out of reach of children and pets. Do not use after the expiration date printed on the packaging. The oral solution should not be frozen.

Disclaimer

This information is intended for educational purposes and does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting, changing, or discontinuing any medication. Individual response to fluoxetine may vary based on health status, genetics, and other factors.

Reviews

Clinical studies and meta-analyses consistently demonstrate fluoxetine’s efficacy in reducing depressive symptoms, with response rates often exceeding 50–60% in compliant patients. Many clinicians report good tolerability and patient satisfaction, particularly regarding its activating properties and minimal weight gain compared to some alternatives. Long-term data support its use in maintenance therapy for preventing relapse. Some criticisms include its potential for initial activation side effects and drug interactions, though these are generally manageable with careful dosing and monitoring.