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Fluoxetine

Brands and Forms

  • Prozac
    • capsule: 10mg, 20mg, 40mg
    • tablet: 10mg
    • oral solution: 20mg/5ml
  • Prozac Weekly
    • capsule: 90mg
  • Fontex
  • Seromex
  • Seronil
  • Sarafem
  • Ladose
  • Fluctin
  • Fluox
  • Depress
  • Lovan

Uses of Fluoxetine

Fluoxetine is commonly used for treating Depressive Disorders (including Major Depressive Disorder, Dysthymia, and Premenstrual Dysphoric Disorder) and Anxiety Disorders (including Panic Disorder, Generalized Anxiety Disorder, Social Phobia, PTSD, and Obsessive-Compulsive Disorder).

It can also be used for treating Bulimia Nervosa, Binge-Eating Disorder, Hypochondriasis, Body Dysmorphic Disorder, Trichotillomania, Depression in Bipolar Disorder, and impulsive behaviors associated with Borderline Personality Disorder and Dementia.

How Fluoxetine Works

Fluoxetine is an SSRI antidepressant. It blocks serotonin reuptake at the serotonin transporter, and thus boosts serotonin actions in the central nervous system. Fluoxetine also desensitizes serotonin 1a autoreceptors, and has antagonist properties at the serotonin 2c receptor, which could increase norepinephrine and dopamine neurotransmission.

Cautions when Using Fluoxetine

Fluoxetine can induce Manic or Mixed Episodes and Rapid Cycling in people with Bipolar Disorder.

Children and adolescents who use antidepressants like Fluoxetine may develop self-injurious or suicidal behaviors (for more information, see here).

Use with caution in people with a known seizure disorder, and in those who are taking anticoagulant (blood thinning) medication.

Long-term use of SSRI antidepressants like Fluoxetine has been associated with increased risk of osteoporosis and bone fractures in individuals over age 50.

Dangerous heart arrhythmias could occur if Fluoxetine is combined with Thioridazine or Pimozide.

Fluoxetine should not be used during or within 14 days following the administration of an MAOI, because a hypertensive crisis may result.

Dosing of Fluoxetine

The usual therapeutic range of Fluoxetine is 20-60mg/day; higher doses of 80-100mg/day may be required for Obsessive-Compulsive Disorder. It can be given once daily, usually in the morning.

In adults, Fluoxetine is usually started at 20mg/day, and the dose can be raised by 10-20mg every week, though it is common practice to wait 4 weeks at 20mg/day for therapeutic effects to take place before deciding to increase the dose. Dose increases are usually done at 2-week intervals to allow time for therapeutic effects to appear.

An exception to this is in the treatment of Bulemia Nervosa, where it is suggested to reach 60mg/day within the first week of treatment by titrating up from 20mg/day every few days.

In children ages 7 and older, Fluoxetine is usually started at 10mg/day. Thereafter, it is common practice to wait 4 weeks for therapeutic effects to take place before increasing the dose further by 10mg every two weeks.

Prozac Weekly is a form that is taken only once a week. It is to be used at 90mg/week. If the regular daily form was being used previously, then Prozac Weekly should be started 7 days after the last 20mg/day dose.

When wanting to stop this medication, the dose should be decreased gradually over a period of 6-8 weeks. A sudden cessation of the medication can result in an SSRI discontinuation syndrome.

Onset of action

Therapeutic effects are not expected before 2-4 weeks at a dose of 20mg/day. If no significant effects are seen after 6-8 weeks of use, including at least 2 weeks at a dose above 20mg/day, then the medication may not work at all.

Kidney impairment

No dose adjustment required.

Liver impairment

Reduce dose by about half, or give less frequently.

Side-effects of Fluoxetine

Below is a list of most of the reported side-effects of Fluoxetine. Most of these side-effects occur in only a minority of individuals, and many also resolve with time while the medication is continued.

Cardiovascular: vasodilatation; hypertension; palpitations (at least 1%); heart rate abnormalities (very rare).

Central Nervous System: somnolence; insomnia; tremor; fatigue; reduced or increased appetite; decreased libido (see below on managing sexual side-effects); dizziness; yawning; weakness; confusion; impaired concentration; headaches; fever; abnormal dreams; akathisia and other extrapyramidal symptoms (rare); seizures (very rare); serotonin syndrome (very rare).

Dermatologic: excessive sweating; itchiness; rash; hair loss (rare).

Endocrine/Metabolic: weight loss; weight gain; elevated prolactin (very rare); SIADH (very rare).

Eyes, Ears, Nose and Throat: pharyngitis; abnormal vision; runny nose; ear pain; taste perversion; tinnitus.

Gastrointestinal: abdominal pain; appetite loss; constipation; diarrhea; dry mouth; dyspepsia; nausea; flatulence; vomiting; increased appetite; GI hemorrhage (rare, due to the blood-thinning effects of the medication); pancreatitis (very rare); hepatits (very rare).

Genitourinary: ejaculation disorder (see below on managing sexual side-effects); impotence; heavy menstruations; excessive urination.

Hematologic: increases bleeding time (thins the blood); easy bruising; thrombocytopenia; thrombosis.

Muskuloskeletal: risk of osteoporosis and bone fractures with long-term use.

Psychiatric: anxiety; agitation; apathy; worsening depression; suicidal thoughts (overall, Fluoxetine use helps to lower risk of suicide); self-injurious behaviors among children and adolescents; can induce Manic or Mixed Episodes and Rapid Cycling in people with Bipolar Disorder.

Respiratory: upper respiratory tract infection; rhinitis; sinusitis; coughing.

Common side-effects of Fluoxetine

Nausea, dry mouth, diarrhea, headache, insomnia, sweating, sexual dysfunction (about 5%, see below on managing sexual side-effects). Most of these side-effects resolve after a few weeks.

Rare but serious side-effects of note of Fluoxetine

Children and adolescents who use antidepressants like Fluoxetine may develop self-injurious or suicidal behaviors (for more information, see here).

SSRI discontinuation syndrome

Individuals who suddenly stop using Fluoxetine after taking the medication at moderate or high doses over a significant period of time are at risk of developing a discontinuation syndrome, which can include the following symptoms: dizziness, electric shock-like sensations, sweating, nausea, insomnia, tremor, anxiety, restlessness, agitation, depressed mood, irritability, confusion, lethargy, and vertigo. These symptoms usually start anywhere from one day to one week after the medication was stopped, and can persists for days or even weeks.

This syndrome can be treated by restarting the medication at its prior dose. It can be prevented by decreasing the dose gradually over a period of 6-8 weeks when wanting to stop the medication. In rare cases, individuals may experience the discontinuation syndrome even when the medication is being tapered gradually; in such cases, an extremely slow and gradual taper will be necessary.

Fluoxetine may be among the least likely of the antidepressants to cause a signficant discontinuation syndrome because it has a very long half-life.

Managing sexual side-effects of Fluoxetine

The first step to manage this is to try to lower the dose of the Fluoxetine. If this is not possible, or is not an effective solution, then either Bupropion, or Sildenafil (Viagra) or Vardenafil (Levitra), can be added [ref]. (Sildenafil and Vardenafil can be effective for female sexual side-effects as well, including difficulty achieving orgasm [ref, ref]).

Bupropion and Mirtazepine are two antidepressants that tend to have very low rates of sexual side-effects.

Fluoxetine overdose

Unsteadiness, confusion, unresponsiveness, nervousness, respiratory difficulties, vertigo, tremor, elevated blood pressure, movement disorder, hypomania, seizures, somnolence, nausea, tachycardia, vomiting, delirium, ECG abnormalities (eg, QT interval prolongation), hypotension, pyrexia, stupor, syncope, serotonin syndrome, coma. Can be fatal.

Fluoxetine and pregnancy

Category C: some animal studies show adverse effects at very high doses, but no controlled human studies have been done; should only be used in pregnancy if clearly needed and if benefits outweigh potential risks. For further information, see the section on treating Depression in pregnancy.

Medical Monitoring for Fluoxetine

None for healthy individuals.

Drug Interactions with Fluoxetine

  • Caution should be used when combining Fluoxetine with other medications that can increase bleeding time and reduce blood clotting, including Aspirin, NSAIDs, anti-platelet agents, Heparin and Coumadin.
  • Combination with other serotonergic medications, including SSRI antidepressants, could potentially precipitate a serotonin syndrome.
  • Dangerous heart arrhythmias could occur if Fluoxetine is combined with Thioridazine or Pimozide.
  • Fluoxetine should not be used during or within 14 days following the administration of an MAOI, because a hypertensive crisis may result.
  • Fluoxetine can increase blood concentrations of Alprazolam, Carbamazepine, Clozapine, Cyclosporin, Digoxin, Haloperidol, Hydantoins, Propafenone, Trazodone, Warfarin.
  • Fluoxetine can lower blood concentrations of Bupropion.