Fluoxetine: Uses, Dosage, Side Effects and Precautions

Fluoxetine is an SSRI antidepressant prescribed for depression, obsessive-compulsive disorder (OCD), panic disorder and bulimia nervosa. This guide covers fluoxetine uses, how it works, dosage, side effects, precautions, drug interactions, use in pregnancy and breastfeeding and its approximate price in India.

At a Glance

What is Fluoxetine?

Fluoxetine is a selective serotonin reuptake inhibitor commonly prescribed for depression, obsessive-compulsive disorder (OCD), panic disorder and bulimia nervosa. It is thought to increase the amount of serotonin available in the brain, which helps regulate mood and anxiety. By increasing serotonin, it helps people feel more balanced by decreasing anxiety or negative thoughts. Whether it is suitable for other anxiety-related conditions depends on the treating doctor’s clinical judgment and local product approval.

How Fluoxetine Works

Fluoxetine blocks the reuptake (reabsorption) of serotonin by nerve cells in the central nervous system. Serotonin is a chemical messenger that helps regulate mood, anxiety and sleep. With less serotonin being taken back up, more of it remains available to carry signals between nerve cells, which is thought to help ease symptoms of depression and anxiety. The exact way it works is not fully understood.

When to Use Fluoxetine

1. Depression: Reduces symptoms of depression and improves mood. Fluoxetine for depression is used in adults, and in children from 8 years of age.
2. Panic disorder: Helps reduce panic attacks, with or without agoraphobia. This use is for adults.
3. OCD: Helps reduce compulsive behaviors and obsessions. Fluoxetine for OCD is used in adults, and in children according to local product labeling.
4. Bulimia nervosa: Used in adults to reduce binge-eating and vomiting behaviors.

Your doctor decides the diagnosis and whether fluoxetine is the right treatment. Do not self-diagnose or self-medicate.

How to Take Fluoxetine

Fluoxetine is usually taken once a day, commonly in the morning, with or without food. The full effect can take several weeks, so keep taking it as prescribed even if you do not feel better straight away. Your doctor will review from time to time whether you still need it. Treatment may continue for a long time.

Take this medicine only as advised by your doctor or healthcare professional. Do not start, stop, or change the dose on your own.

Fluoxetine Dosage

Fluoxetine dosing depends on the condition being treated and is decided by your doctor. For adults, current labeling describes these usual starting doses:

• Depression: 20 mg once daily in the morning.
• OCD: 20 mg once daily in the morning.
• Panic disorder: 10 mg once daily for the first week, then 20 mg once daily.
• Bulimia nervosa: 60 mg once daily in the morning, which may be built up over several days.

After several weeks, your doctor may adjust the dose based on your response and how well you tolerate the medicine. A lower or less frequent dose may be used in people with liver problems, older adults and people taking several medicines. These figures are for information only and are not a dosing guide. Do not raise, lower or stop the dose without your doctor’s advice.

Children and adolescents: In children, fluoxetine is used mainly for depression from 8 years of age. US labeling also approves it for OCD from 7 years of age, while approval for OCD in children can differ between countries, so the local product labeling applies. Safety and effectiveness have not been established below these ages, and panic disorder and bulimia nervosa uses are for adults. Pediatric use must be decided, prescribed and monitored by a qualified doctor or specialist. Dosing is weight-based and set by the doctor according to the child’s condition, age, weight, the form of medicine and response, so parents and caregivers should never calculate or adjust the dose themselves. Height and weight may be checked from time to time.

Side Effects of Fluoxetine

Common side effects: Nausea, insomnia, sexual dysfunction (such as lower sex drive, delayed ejaculation or difficulty reaching orgasm), dizziness. Other effects include headache, diarrhoea, dry mouth, reduced appetite, tiredness or drowsiness, nervousness or anxiety, tremor and sweating. Fluoxetine can affect judgment and coordination, so avoid driving or using machinery until you know how it affects you.

Less common but serious effects needing prompt medical attention:

• New or worsening depression, thoughts of suicide or self-harm, agitation or significant changes in behavior, especially in children, adolescents and young adults.
• Signs of serotonin syndrome, such as agitation, hallucinations, fast heartbeat, fever, heavy sweating, shivering, muscle stiffness or twitching, vomiting or diarrhoea. The risk is higher when fluoxetine is combined with other medicines that raise serotonin.
• A serious allergic reaction or rash, such as hives, swelling or difficulty breathing.
• Unusual bleeding or bruising, particularly if you also take aspirin, NSAIDs or blood thinners.
• Symptoms of low sodium (hyponatremia), such as headache, confusion, weakness or unsteadiness. Older adults and people taking diuretics may be more likely to be affected.
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• Unusually high energy or elevated mood (mania).
• Fainting, palpitations or an irregular heartbeat, which can reflect a heart rhythm problem.

If symptoms are severe, or you have thoughts of harming yourself, go to the nearest hospital or contact emergency services immediately.

Suicidal Thoughts and Young People

Depression and some other conditions that fluoxetine treats can themselves increase the risk of suicidal thoughts. In short-term studies, antidepressants increased the risk of suicidal thoughts and behavior in children, adolescents and young adults up to 24 years of age, mainly in the first few months of treatment and after dose increases or decreases. This does not mean treatment should be avoided. It means close attention matters. Families and caregivers are advised to watch for new or worsening depression, agitation, irritability, unusual behavior changes or talk of self-harm, and to tell the doctor promptly. Do not wait for the next appointment.

Who Should Not Take Fluoxetine

Fluoxetine must not be used with MAOI antidepressants, or within 14 days of stopping one. At least 5 weeks should pass after stopping fluoxetine before starting an MAOI. It should not be started in a person being treated with linezolid or intravenous methylene blue. It must also not be used with pimozide or thioridazine, and thioridazine should not be used within 5 weeks of stopping fluoxetine.

Fluoxetine Precautions

Tell your doctor if you have bipolar disorder or a history of mania, seizures, bleeding problems or take blood thinners, diabetes (blood sugar may change), liver disease, a heart rhythm problem such as long QT, narrow-angle glaucoma, low sodium, or take diuretics. Also tell your doctor if you have had an allergic reaction or serious side effect with fluoxetine or another SSRI.

Monitoring

Routine blood tests or an ECG are not required for everyone taking fluoxetine. What is checked depends on your age, the condition being treated, medical history, risk factors, symptoms and other medicines. Monitoring of mood and any suicidal thoughts or unusual behavior is important for all patients, especially at the start of treatment and after dose changes. Where the doctor considers it necessary, they may also check weight and appetite, height and weight in children, blood sugar in people with diabetes, sodium if symptoms of low sodium appear, and heart rhythm (ECG) in people with heart rhythm risk factors.

Stopping Fluoxetine

Do not stop fluoxetine on your own, as symptoms of the condition can return or worsen. Fluoxetine and its active breakdown product leave the body slowly over weeks, so discontinuation symptoms may be milder or appear later than with shorter-acting SSRIs, and many people have none. When they do occur, such as dizziness, irritability, anxiety, sleep problems, headache or electric-shock-like sensations, they are usually temporary, but they can sometimes be troublesome. Your doctor will decide whether and how to lower the dose gradually. Because fluoxetine stays in the body for weeks, its effects and its interactions with other medicines can continue for some time after the last dose.

Fluoxetine in Pregnancy and Breastfeeding

• Pregnancy: Fluoxetine can be used during pregnancy if needed. It is a risk-benefit decision between you and your doctor, weighing the risks of untreated depression or other conditions against possible medicine-related risks. Do not stop it on your own, as stopping can increase the chance of the condition coming back. Antidepressants of this type taken late in pregnancy have been linked to breathing and adaptation problems in newborns, so your doctor and delivery team should know you are taking it.
• Breastfeeding: Fluoxetine passes into breast milk. If it is needed, this is not by itself a reason to stop breastfeeding, and your doctor will decide what is appropriate for you. The baby may be monitored for effects such as irritability, colic, poor feeding, excessive sleepiness or poor weight gain.

Fluoxetine Drug Interactions

• MAOIs, linezolid and intravenous methylene blue: Serious interaction (serotonin syndrome). See the washout periods above.
• Pimozide and thioridazine: Must not be combined with fluoxetine because of heart rhythm risks.
• Other serotonin-raising medicines: Other antidepressants, triptans, tramadol and other opioids, lithium, buspirone, amphetamines and St John’s Wort can increase the risk of serotonin syndrome.
• NSAIDs, aspirin and blood thinners such as warfarin: Can increase the risk of bleeding.
• Medicines processed by the CYP2D6 liver enzyme: Fluoxetine can raise levels of tricyclic antidepressants, some antipsychotics (such as haloperidol and clozapine) and some heart rhythm medicines (such as flecainide and propafenone), so doses may need review.
• Phenytoin and carbamazepine: Fluoxetine can raise their levels and cause toxicity.
• Alprazolam and diazepam: Fluoxetine can increase or prolong their effects.
• Other medicines that affect heart rhythm: Some antibiotics, antipsychotics and antiarrhythmics can add to heart rhythm risk.

This is not a complete list. The full interaction profile depends on your medicines and clinical situation. Tell your doctor or pharmacist about all prescription medicines, over-the-counter medicines, herbal products and supplements you use.

Alcohol

Alcohol is best avoided because it can add to drowsiness and affect judgment.

Fluoxetine Brands, Strengths and Approximate Price in India

Common brands in India: Prodep and Fludac. Fluoxetine 20 mg capsules are widely available, and strengths and forms vary by brand and market.

Approximate price: Prodep 20 mg capsule, strip of 10, about ₹34 to ₹48. Fludac 20 mg capsule, strip of 15, about ₹53 to ₹70. The actual price varies by brand, pharmacy, location, pack size and date.

How HealthPil Can Help

Medicines should be started, adjusted, or stopped only under the guidance of a qualified healthcare professional. If you have questions about this medicine, its side effects, or your treatment plan, you can consult a doctor through HealthPil, including mental health specialists.