Fluoxetine

Fluoxetine belongs to the class of antidepressants known as selective serotonin reuptake inhibitors (SSRIs) ¹, ², ³. Fluoxetine works by increasing the amount of serotonin, a natural substance in the brain that helps maintain mental balance. Fluoxetine is a medication that has been used to treat depression, obsessive-compulsive disorder (OCD, bothersome thoughts that won’t go away and the need to perform certain actions over and over), Tourette’s syndrome, bulimia nervosa, panic disorder (a type of anxiety disorder characterized by recurring, unexpected panic attacks, which are sudden episodes of intense fear or discomfort, often accompanied by physical symptoms, and persistent worry about future attacks), and premenstrual dysphoric disorder [PMDD] symptoms (a more severe form of premenstrual syndrome [PMS] characterized by extreme mood swings, bloating, irritability, breast tenderness and depression, occurring in the week or two before menstruation). Fluoxetine has also been used to treat body dysmorphic disorder, borderline personality disorder, hot flushes of menopause, post traumatic stress disorder (PTSD), alcoholism, attention-deficit/hyperactivity disorder (ADHD), sleep disorders, headaches, mental illness, sexual problems, phobias and Raynaud’s phenomenon. Fluoxetine is also used along with olanzapine (Zyprexa) to treat depression that did not respond to other medications and episodes of depression in people with bipolar disorder type 1 (manic-depressive disorder; a disease that causes episodes of depression, episodes of mania, and other abnormal moods). Fluoxetine may be prescribed for other uses; ask your doctor for more information.

Fluoxetine was approved for use in the United States in 1987 and it became one of the most widely used antidepressant medications, more than 20 million prescriptions being written yearly ².

Fluoxetine is available as tablets, delayed-release (releases the medication in the intestine) capsules of 10, 20 and 40 mg and in an oral solution (liquid) of 20 mg/5 mL, in multiple generic forms and under the brand names of Prozac and Sarafem. Fixed combinations of fluoxetine with olanzapine (Symbyax and generic forms) are also available. A long acting formulation of 90 mg of fluoxetine has been developed for once weekly dosing (Prozac weekly).

Fluoxetine may be taken with or without food. Fluoxetine capsules, tablets, and liquid are usually taken once a day in the morning or twice a day in the morning and at noon. The recommended dosage of standard formulations of fluoxetine in adults is 20 mg once daily, increasing to 40 mg daily if necessary and not exceeding 80 mg daily.

Fluoxetine delayed-released capsules are usually taken once a week. Take fluoxetine at around the same time(s) every day. Swallow the delayed-release capsules whole; do not cut, crush, or chew them. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take fluoxetine exactly as directed. Your doctor may start you on a low dose of fluoxetine and gradually increase your dose. Do not take more or less of it or take it more often than prescribed by your doctor.

It may take 4 to 5 weeks or longer before you feel the full benefit of fluoxetine. Continue to take fluoxetine even if you feel well. Do not stop taking fluoxetine without talking to your doctor. If you suddenly stop taking fluoxetine, you may experience withdrawal symptoms such as mood changes, irritability, agitation, dizziness, numbness or tingling in the hands or feet, anxiety, sweating, confusion, headache, tiredness, and difficulty falling asleep or staying asleep. Your doctor will probably decrease your dose gradually.

Common side effects of fluoxetine are drowsiness, dyspepsia, nausea, headache, increased sweating, increased appetite, weight gain and sexual dysfunction.

How does Fluoxetine work?

Fluoxetine belongs to the class of antidepressants known as selective serotonin reuptake inhibitors (SSRIs) ¹, ², ³. Fluoxetine exerts its antidepressant effects by blocking the reuptake of serotonin in the presynaptic serotonin neurons by blocking the reuptake transporter protein in the presynaptic terminal. Due to Fluoxetine’s action on the reuptake of serotonin, fluoxetine produces an activating effect, and due to its long half-life, the initial antidepressant effect emerges within 2 to 4 weeks. Fluoxetine also has mild activity at the serotonin 5-HT2A and 5-HT2C receptors.

Fluoxetine has minimal activity on noradrenergic reuptake.

Pharmacokinetics

• Absorption: Peak plasma concentrations of fluoxetine are attained after 6 to 8 hours. Fluoxetine is well absorbed with a bioavailability of 70% to 90%. Food does not appear to impact the bioavailability of fluoxetine, but it may slow its absorption by 1 to 2 hours, which is not clinically significant. Thus, fluoxetine may be administered with or without food.
• Distribution: Fluoxetine has plasma protein binding of approximately 94.5%, bound to albumin and alpha-1 glycoprotein. Fluoxetine readily crosses the blood-brain barrier, with a brain-to-plasma ratio of 2.6:1 in humans. The volume of distribution (Vd) of fluoxetine and its metabolite ranges between 20 to 42 L/kg. Some studies report that fluoxetine has the maximum volume of distribution (Vd) of any SSRI (between 14 and 100 L/kg) ⁴
• Metabolism: Fluoxetine’s active metabolite is norfluoxetine, produced when the cytochrome P450 enzyme (CYP2D6) acts on it. Prescribers must remember that fluoxetine has several drug-drug interactions due to its metabolism through the CYP2D6 isoenzyme. Additionally, norfluoxetine can have an inhibitory effect on CYP3A4. Fluoxetine has a half-life of 2 to 4 days, and its active metabolite norfluoxetine has a half-life of 7 to 9 days ⁵, ⁶. Approximately 7% of individuals definitively exhibit poor metabolism of fluoxetine due to reduced activity of CYP2D6 ⁷.
• Elimination: Fluoxetine and norfluoxetine have long elimination half-lives, leading to the presence of the drug in the body for several weeks, even after stopping its use. This has important implications when discontinuing fluoxetine and prescribing medications that may interact with fluoxetine and norfluoxetine after discontinuation. The metabolism of fluoxetine is extensive, resulting in approximately 2.5% of the administered dose being excreted unchanged in the urine ⁸.

What is Fluoxetine used for?

Fluoxetine is a SSRI medication that has received FDA approval to treat major depressive disorder (8 years of age and older), obsessive-compulsive disorder (OCD, bothersome thoughts that won’t go away and the need to perform certain actions over and over) (7 years of age and older), panic disorder (a type of anxiety disorder characterized by recurring, unexpected panic attacks, which are sudden episodes of intense fear or discomfort, often accompanied by physical symptoms, and persistent worry about future attacks with or without agoraphobia), bulimia nervosa ⁹, ¹⁰, ¹¹. The American Psychiatric Association guidelines recommend fluoxetine as first-line pharmacotherapy along with cognitive behavioral therapy (CBT) for patients with bulimia nervosa ¹². Fluoxetine is also used as an add-on with olanzapine (Zyprexa) to treat depression that did not respond to other medications and episodes of depression in people with bipolar disorder type 1 (a mental health condition characterized by at least one manic episode, which may be followed by depressive or hypomanic episodes, and can involve psychosis).

Non-FDA-approved uses for fluoxetine include Tourette’s syndrome, binge eating disorder, social anxiety disorder, body dysmorphic disorder, premenstrual dysphoric disorder [PMDD] symptoms (a more severe form of premenstrual syndrome [PMS] characterized by extreme mood swings, bloating, irritability, breast tenderness and depression, occurring in the week or two before menstruation), borderline personality disorder, Raynaud’s phenomenon, and selective mutism ¹³, ¹⁴.

The American Psychological Association endorses fluoxetine for post traumatic stress disorder (PTSD) ¹⁵.

Fluoxetine has also been used to treat hot flushes of menopause, alcoholism, attention-deficit/hyperactivity disorder (ADHD), sleep disorders, headaches, mental illness, sexual problems and phobias. Fluoxetine may be prescribed for other uses; ask your doctor for more information.

Fluoxetine Contraindications

Contraindications to fluoxetine include hypersensitivity to fluoxetine or any component in its formulation. This drug is also contraindicated with the concurrent use of monoamine oxidase inhibitors (current use of monoamine oxidase (MAO) inhibitor or within 2 weeks of discontinuing the monoamine oxidase (MAO) inhibitor) due to the risk of serotonin syndrome.

Never initiate fluoxetine in a patient receiving linezolid ¹⁶.

Do not give fluoxetine with pimozide or thioridazine due to the risk of QT prolongation ¹⁷.

Use Fluoxetine with caution in those with a history of seizures or elderly patients.

Before taking Fluoxetine

You should not use Fluoxetine if you are allergic to fluoxetine, if you also take pimozide or thioridazine. Tell your doctor and pharmacist if you are allergic to fluoxetine, any other medications, or any of the ingredients in fluoxetine capsules, tablets, or solution. Ask your pharmacist for a list of the ingredients.

Do not use fluoxetine if you have used an monoamine oxidase (MAO) inhibitor in the past 14 days. A dangerous drug interaction could occur. Monoamine oxidase (MAO) inhibitors include isocarboxazid (Marplan), linezolid (Zyvox), methylene blue, rasagiline, phenelzine (Nardil), selegiline (Emsam, Zelapar), and tranylcypromine (Parnate). You must wait at least 14 days after stopping an monoamine oxidase (MAO) inhibitor before you take fluoxetine. You must wait 5 weeks after stopping fluoxetine before you can take thioridazine or an monoamine oxidase (MAO) inhibitor.

Tell your doctor about all other antidepressants you take, especially Celexa, Cymbalta, Desyrel, Effexor, Lexapro, Luvox, Oleptro, Paxil, Pexeva, Symbyax, Viibryd, or Zoloft.

To make sure fluoxetine is safe for you, tell your doctor if you have ever had:

• Bipolar disorder (mood disorder with mania and depression)
• Bleeding problems
• Diabetes
• Drug abuse
• Angle-closure glaucoma. You should know that fluoxetine may cause angle-closure glaucoma, a condition where the fluid is suddenly blocked and unable to flow out of the eye causing a quick, severe increase in eye pressure which may lead to a loss of vision. Talk to your doctor about having an eye examination before you start taking fluoxetine. If you have nausea, eye pain, changes in vision, such as seeing colored rings around lights, and swelling or redness in or around the eye, see your doctor or get emergency medical treatment right away.
• Hyponatremia (low sodium in the blood)
• Mania
• Seizures or epilepsy
• Sexual problems—Use with caution. May make these conditions worse.
• Heart attack or stroke
• Heart failure
• Heart rhythm problems such as prolonged QT interval (a rare heart problem that may cause irregular heartbeat, fainting, or sudden death)
• Cirrhosis of the liver or liver disease—Use with caution. The effects may be increased because of slower removal of the medicine from the body.
• Urination problems
• Suicidal thoughts
• Electroconvulsive therapy (ECT), procedure in which small electric shocks are administered to the brain to treat certain mental illnesses.
• Hypokalemia (low potassium in the blood) or
• Hypomagnesemia (low magnesium in the blood)—May cause side effects to become worse.
• Liver impairment: In patients with liver cirrhosis, the clearance of fluoxetine and its active metabolite (norfluoxetine) decreases, thus increasing the elimination of half-lives of these substances. Therefore, a lower/less frequent dose of fluoxetine should be used in patients with cirrhosis. In addition, caution is warranted when using fluoxetine in patients with diseases or conditions that could affect its metabolism.
• Kidney impairment: No dose adjustment of fluoxetine is required in patients with renal impairment. A study suggests that directly observed, once-weekly fluoxetine could be a feasible and well-tolerated treatment option for hemodialysis patients ¹⁸

Also tell your doctor if you have a low level of potassium, magnesium, or sodium in your blood.

Tell your doctor if you have recently had a heart attack and if you have or have ever had a slow or irregular heartbeat, heart failure, or any other heart problems; high blood pressure; bleeding problems; a stroke; liver or kidney disease.

The following nonprescription or herbal products may interact with fluoxetine: St. John’s wort; tryptophan. Be sure to let your doctor and pharmacist know that you are taking these medications before you start taking fluoxetine. Do not start any of these medications while taking fluoxetine without discussing with your doctor.

Some young people have thoughts about suicide when first taking an antidepressant. Your doctor should check your progress at regular visits. Your family or other caregivers should also be alert to changes in your mood or symptoms.

Older adults may be more sensitive to the effects of fluoxetine.

Ask your doctor about taking fluoxetine if you are pregnant, especially if you are in the last few months of your pregnancy, or if you plan to become pregnant or are breastfeeding. Taking an SSRI antidepressant during late pregnancy may cause serious medical complications in the baby if it is taken during the last months of pregnancy. However, you may have a relapse of depression if you stop taking your antidepressant. Tell your doctor right away if you become pregnant. If you are pregnant, your name may be listed on a pregnancy registry to track the effects of fluoxetine on the baby.

If you are breastfeeding, tell your doctor if you notice agitation, fussiness, feeding problems, or poor weight gain in the nursing baby.

You should know that fluoxetine may make you drowsy and may affect your judgment, thinking, and movements. Do not drive a car or operate machinery until you know how fluoxetine affects you. Remember that alcohol can add to the drowsiness caused by fluoxetine.

Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to Fluoxetine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Children

Appropriate studies performed to date have not demonstrated pediatric-specific problems that would limit the usefulness of fluoxetine in children. However, safety and efficacy have not been established to treat depression in children younger than 8 years of age, to treat obsessive-compulsive disorder in children younger than 7 years of age, and to treat depression that is part of bipolar disorder in children younger than 10 years of age.

Appropriate studies have not been performed on the relationship of age to the effects of fluoxetine in children with bulimia nervosa, panic disorder, or treatment resistant depression. Safety and efficacy have not been established.

Fluoxetine is FDA-approved for administration in pediatric patients with major depressive disorder (clinical depression) and obsessive-compulsive disorder (OCD). As with other SSRIs, decreased weight gain is associated with administering fluoxetine in children and adolescent patients. The dose for children with major depressive disorder (clinical depression) and obsessive-compulsive disorder (OCD) is 10 mg once daily. According to the American Academy of Child and Adolescent Psychiatry (AACAP), it is recommended to offer selective serotonin reuptake inhibitor (SSRI) medication, particularly fluoxetine, to children and adolescents diagnosed with major depressive disorder. For those who respond positively to acute treatment with fluoxetine, the American Academy of Child and Adolescent Psychiatry (AACAP) suggests continuing with fluoxetine alone or combining it with cognitive-behavioral therapy to prevent the relapse or recurrence of major depressive disorder ¹⁹.

Extensive metareview study results show that fluoxetine offers a strong risk-benefit ratio compared to other antidepressants in youth. This finding suggests that fluoxetine could be recommended as the initial treatment of choice for depressive disorders in children and adolescents ²⁰.

Elderly

Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of fluoxetine in the elderly ²¹. However, elderly patients are more likely to have hyponatremia (low sodium in the blood) than younger adults, which may require caution and an adjustment in the dose for patients receiving fluoxetine.

Pregnancy

Fluoxetine has been studied in women having medical treatments because they were already having a hard time getting pregnant. In these studies, those who took fluoxetine got pregnant at the same rate as those who did not take fluoxetine ²².

Out of all babies born each year, about 3 out of 100 (3%) will have a birth defect. Doctors look at research studies to try to understand if an exposure, like fluoxetine, might increase the chance of birth defects in a pregnancy. Fluoxetine use is not expected to increase the chance of birth defects. There are reports of over 10,000 pregnancies exposed to fluoxetine in the first trimester (when many major birth defects can happen). No pattern of birth defects has been found and most studies have not found an increased chance of birth defects related to fluoxetine use.

Some studies have suggested an increased chance of heart defects or other birth defects. However, there is no proven increased chance of birth defects directly related to fluoxetine.

Some studies suggest a higher chance of preterm delivery (birth before week 37) or low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth) with the use of fluoxetine in pregnancy. However, research has also shown that when conditions such as depression or anxiety are untreated or undertreated during pregnancy, there could be an increased chance of pregnancy complications. This makes it hard to know if it is the medication, the underlying condition, or other factors that might increase the chance for these problems.

Some, but not all, studies have suggested that when women who are pregnant take SSRIs during the second half of pregnancy, their babies might have an increased chance for a serious lung condition called persistent pulmonary hypertension (PPH). Persistent pulmonary hypertension happens in 1 or 2 out of 1,000 births. A recent report that combined results from several studies suggested the chance for persistent pulmonary hypertension might be increased if an SSRI was used during pregnancy. However, it was not clear if this was due to medication exposure or to other exposures that people who take SSRIs have in common, such as higher rates of smoking. Data from studies suggest the overall chance for persistent pulmonary hypertension when an SSRI is used in pregnancy is less than 1/100 (less than 1%).

The use of fluoxetine during pregnancy and/or in the third trimester can cause temporary symptoms in newborns soon after birth. These symptoms are sometimes referred to as withdrawal. Symptoms include being irritable and/or jittery, crying, tight muscles, trouble breathing, unusual sleep patterns, tremors (shivers), and/or trouble eating. In most cases symptoms are mild and go away in a few weeks with no treatment, or with only supportive care. Not all babies exposed to fluoxetine will have these symptoms. There might be a higher chance for withdrawal symptoms if other psychiatric medications are also taken with fluoxetine during pregnancy. It is important that your doctor know you are taking fluoxetine so that if symptoms occur your baby can get the care that is best for them.

Does taking fluoxetine in pregnancy affect future behavior or learning for the child?

A few studies have looked at the development of children from age 16 months to 7 years and did not find differences between children who were exposed to fluoxetine during pregnancy and those who were not. Most studies found no increase in attention deficit hyperactivity disorder (ADHD) in children exposed to SSRIs like fluoxetine during pregnancy. Most studies also find that SSRIs like fluoxetine do not appear to increase the chance of autism spectrum disorders (ASD) after adjusting for factors such as maternal illness.

Breastfeeding

Fluoxetine gets into breast milk and most reports find no side effects in breastfed babies ²². In a small number of cases, irritability, vomiting, diarrhea, and less sleep have been reported. One study noted slightly less weight gain in infants exposed to fluoxetine via breast milk; however, this would likely only be an issue if the infant’s weight gain was already a concern ²². One study showed that mental and physical development was normal for infants exposed to fluoxetine in breast milk in their first year of life ²². Studies in women breastfeeding have demonstrated harmful infant effects ²³. If you suspect the baby has any symptoms (such as irritability, vomiting, diarrhea, trouble sleeping, or trouble gaining weight) contact the child’s doctor.

The product label for fluoxetine recommends women who are breastfeeding not use this medication. But the benefit of treating your condition might outweigh possible risks. Your doctor can talk with you about using fluoxetine and what treatment is best for you. Be sure to talk to your doctor about all your breastfeeding questions.

An alternative to Fluoxetine should be prescribed or you should stop breastfeeding while using Fluoxetine.

If a man takes fluoxetine, could it affect fertility or increase the chance of birth defects?

Fluoxetine and other SSRIs have been reported to cause some sexual side effects, such as lower sexual desire or problems with ejaculation. This can affect a man’s fertility (ability to get a woman pregnant). Studies looking at fluoxetine in a small number of men have reported that sperm quality can be affected (but still within the normal range) with long-term fluoxetine use. The sperm quality improved when fluoxetine was stopped. In general, exposures that men have are unlikely to increase risks to a pregnancy.

Drug Interactions

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking Fluoxetine, it is especially important that your doctor know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using Fluoxetine with any of the following medicines is not recommended. Your doctor may decide not to treat you with Fluoxetine or change some of the other medicines you take.

• Bepridil
• Bromopride
• Cisapride
• Clorgyline
• Dronedarone
• Isocarboxazid
• Levoketoconazole
• Levomethadyl
• Linezolid
• Mavacamten
• Mavorixafor
• Mesoridazine
• Methylene Blue
• Nialamide
• Ozanimod
• Phenelzine
• Pimozide
• Piperaquine
• Procarbazine
• Rasagiline
• Safinamide
• Saquinavir
• Selegiline
• Sparfloxacin
• Terfenadine
• Thioridazine
• Toloxatone
• Tranylcypromine
• Ziprasidone

Using Fluoxetine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

• Abciximab
• Abiraterone Acetate
• Abiraterone Acetate, Micronized
• Aceclofenac
• Acemetacin
• Acenocoumarol
• Adagrasib
• Alfentanil
• Alfuzosin
• Almotriptan
• Amineptine
• Amiodarone
• Amisulpride
• Amitriptyline
• Amitriptylinoxide
• Amoxapine
• Amphetamine
• Amtolmetin Guacil
• Anagrelide
• Anileridine
• Apixaban
• Apomorphine
• Aprindine
• Ardeparin
• Argatroban
• Aripiprazole
• Aripiprazole Lauroxil
• Arsenic Trioxide
• Asenapine
• Aspirin
• Astemizole
• Atazanavir
• Atomoxetine
• Azithromycin
• Bedaquiline
• Belzutifan
• Bemiparin
• Benzhydrocodone
• Benzphetamine
• Betrixaban
• Plus many more not on this list.

Using Fluoxetine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

• Alprazolam
• Cyproheptadine
• Delavirdine
• Diazepam
• Ginkgo
• Metoprolol.

Fluoxetine Dosage

The dose of Fluoxetine will be different for different patients. Follow your doctor’s orders or the directions on the label. The following information includes only the average doses of Fluoxetine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

For oral dosage forms (capsules, delayed-release capsules, pulvules, or solution)

• For bulimia nervosa
  • Adults: 60 milligrams (mg) once a day in the morning.
  • Children: Use and dose must be determined by your doctor.
• For depression
  • Adults: At first, 20 milligrams (mg) once a day in the morning. Your doctor may adjust your dose as needed. If you are taking more than 20 mg per day, you may take the capsule once a day in the morning or 2 times a day (eg, morning and noon). However, the dose is usually not more than 80 mg per day.
  • Children 8 years of age and older: At first, 10 or 20 mg once a day in the morning. Your doctor may adjust your dose as needed.
  • Children younger than 8 years of age: Use and dose must be determined by your doctor.

Major depressive disorder

The typical starting dose of fluoxetine for major depressive disorder (clinical depression) is 20 mg daily. The maximum recommended dose of fluoxetine for major depressive disorder is 80 mg daily ²⁴.

Depression associated with bipolar disorder (combination with olanzapine)

• Adults: At first, 20 milligrams (mg) of fluoxetine and 5 mg of olanzapine once a day, taken in the evening. Your doctor may adjust your dose as needed. However, the dose is usually not more than 50 mg of fluoxetine and 12 mg of olanzapine per day.
• Children 10 years of age and older: At first, 20 milligrams (mg) of fluoxetine and 2.5 mg of olanzapine once a day, taken in the evening. Your doctor may adjust your dose as needed. However, the dose is usually not more than 50 mg of fluoxetine and 12 mg of olanzapine per day.
• Children younger than 10 years of age: Use and dose must be determined by your doctor.

Treatment resistant depression (combination with olanzapine)

• Adults: At first, 20 milligrams (mg) of fluoxetine and 5 mg of olanzapine once a day, taken in the evening. Your doctor may adjust your dose as needed. However, the dose is usually not more than 50 mg of fluoxetine and 20 mg of olanzapine per day.
• Children: Use and dose must be determined by your doctor.

Obsessive-compulsive disorder (OCD)

• Adults: At first, 20 milligrams (mg) once a day in the morning. Your doctor may adjust your dose as needed. However, the dose is usually not more than 80 mg per day. The typical maintenance dose for obsessive-compulsive disorder (OCD) is 20 to 60 mg.
• Children 7 years of age and older: At first, 10 mg once a day in the morning. Your doctor may adjust your dose as needed. However, the dose is usually not more than 60 mg per day.
• Children younger than 7 years of age: Use and dose must be determined by your doctor.

Panic disorder

• Adults: At first, 10 milligrams (mg) once a day in the morning. Your doctor may adjust your dose as needed. After 1 week, consider increasing the fluoxetine to 20 mg daily. The maximum recommended dose of fluoxetine for panic disorder is 60 mg daily.
• Children: Use and dose must be determined by your doctor.

Premenstrual dysphoric disorder (PMDD)

• Adults: At first, 20 milligrams (mg) once a day in the morning. Your doctor may have you take 20 mg every day of your menstrual cycle or for only 15 days of your cycle. Your doctor may adjust your dose as needed. However, the dose is usually not more than 80 mg per day.
• Children: Use and dose must be determined by your doctor.

Bulimia nervosa

The American Psychiatric Association guidelines recommend cognitive-behavioral therapy (CBT) as the primary treatment for adults with bulimia nervosa. If there is minimal or no response to psychotherapy alone within 6 weeks, prescribing 60 mg of fluoxetine daily is recommended ¹².

Missed Dose

If you miss a dose of Fluoxetine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Monitoring

A thorough assessment of depression and suicidal risk, particularly at the beginning of Fluoxetine therapy or when doses are changed, anxiety/panic attacks, social functioning, mania/mood lability, and features of serotonin syndrome ²⁵, ²⁶. The Patient Health Questionnaire-9 (PHQ-9) and Hamilton Depression Rating Scale (HAM-D/HDRS) should be monitored ²⁷, ²⁸, ²⁹.

No routine laboratory testing is necessary for healthy individuals. However, in older and population-specific patients, clinicians may order blood glucose and liver function tests. In addition, prescribers may order an ECG for patients with risk factors for QT prolongation and ventricular arrhythmias. Pediatric patients’ height and weight should be monitored periodically when receiving fluoxetine.

The American Society of Regional Anesthesia (ASRA) suggests a washout period of approximately 5 weeks before interventional spine and pain procedures due to the long half-life of fluoxetine to decrease the risk of bleeding ³⁰.

Fluoxetine side effects

Fluoxetine may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• nervousness
• anxiety
• difficulty falling asleep or staying asleep
• nausea
• diarrhea
• dry mouth
• heartburn
• yawning
• weakness
• uncontrollable shaking of a part of the body
• loss of appetite
• weight loss
• unusual dreams
• stuffy nose
• sexual problems in males; decreased sex drive, inability to get or keep an erection, or delayed or absent ejaculation
• sexual problems in females; decreased sex drive, or delayed orgasm or unable to have an orgasm
• excessive sweating
• headache, confusion, weakness, difficulty concentrating, or memory problems

Some side effects can be serious. If you experience any of the following symptoms or those listed in the IMPORTANT WARNING or SPECIAL PRECAUTIONS section, see your doctor immediately:

• rash
• hives or blisters
• itching
• fever
• joint pain
• swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs
• difficulty breathing or swallowing
• agitation, fever, sweating, confusion, fast or irregular heartbeat, shivering, severe muscle stiffness or twitching, hallucinations, loss of coordination, nausea, vomiting, or diarrhea
• fast, slow, or irregular heartbeat
• shortness of breath
• dizziness or fainting
• seizures
• abnormal bleeding or bruising

Fluoxetine may decrease appetite and cause weight loss in children. Your child’s doctor will watch his or her growth carefully. Talk to your child’s doctor if you have concerns about your child’s growth or weight while he or she is taking this medication. Talk to your child’s doctor about the risks of giving fluoxetine to your child.

Fluoxetine may cause other side effects. See your doctor if you have any unusual problems while taking fluoxetine.

Fluoxetine Toxicity

Fluoxetine is rarely lethal in monotherapy overdose. However, when taken with alcohol, it may cause ataxia and respiratory depression. Fluoxetine may cause serotonin syndrome (also knownn as serotonin toxicity, which is a potentially life-threatening drug reaction that results from having too much serotonin in your body) when taken in excessive amounts or combined with other agents that increase serotonin levels ³¹, ³².

Management of Fluoxetine Overdose

In the case of SSRI overdose, the goal is to provide supportive therapy. This support can be in the form of airway protection, serial ECGs to monitor for cardiotoxicity, administration of benzodiazepines for sedation, and GI decontamination with activated charcoal. Serotonin syndrome is treatable with the administration of cyproheptadine ³³, ³⁴.

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