Fluoxetine (Prozac, Fontex, Seromex, Seronil, Sarafem, Fluctin)
Fluoxetine was the first SSRI antidepressant approved for use in the US and was introduced by Eli Lilly in 1987. The patent expired in 2001 and fluoxetine is now available as a generic medication.
Fluoxetine was derived from diphenhydramine (Benadryl), an antihistamine that was known to have antidepressant properties. The introduction of SSRI antidepressants dramatically changed the treatment of depression and SSRIs have become the most prescribed medications in the world.
The Bottom Line: What You Really Need to Know
- Fluoxetine (Prozac) is used to treat depression and OCD in adults and children. It is the only medication approved in the USA to treat depression in children. It is also used to treat bulimia, panic attacks, Premenstrual Dysphoric Disorder, hypochondriasis and body dysmorphic disorder.
- The usual dose of fluoxetine is 20-80 mg/day in adults and 10-60 mg/day in children, depending on what it is being used for. Be sure to take it exactly as your doctor directs.
- There is an extended release fluoxetine available (Prozac Weekly). It works for some people who take 20 mg/day of fluoxetine.
- Fluoxetine interacts with many different medications. Make sure you tell your physician and pharmacist about all medications that you take, including herbal remedies and teas, over the counter medications, homeopathic and alternative treatments, vitamins, supplements and medications you only take occasionally.
- If you have surgery, make sure your surgeon knows you take fluoxetine. It can interact with anesthetics.
- It may take two weeks or more before you start feeling better.
- Talk to your doctor before you stop taking fluoxetine. Your dose may need to be tapered down slowly to prevent uncomfortable withdrawal symptoms.
- Most people experience a few mild side effects, like dry mouth or constipation, when they begin taking fluoxetine. They usually go away with time.
- If you experience loss of interest in sex or diminished sexual ability, talk to your doctor about it.
- Fluoxetine is contraindicated in pregnancy. It is associated with birth defects and lung problems in the newborn.
- Have a friend or family member check in with you every day for the first few weeks that you take fluoxetine. Ask him or her to help you monitor your condition for:
- Worsening depression
- Restlessness, irritability, agitation, hostility or aggression
- Unusual thoughts or thoughts of suicide
- Report any serious or unusual side effects to your doctor.
Uses of fluoxetine
Fluoxetine is approved for the treatment of depression and obsessive compulsive disorder in adults and children. It is the only antidepressant approved in the US for use in children. It is also approved to treat bulimia, panic disorder, premenstrual dysphoric disorder (PMDD), hypochondriasis, and body dysmorphic disorder. It is used off label to treat a wide range of other problems such as alcoholism, attention deficit disorder (ADD), borderline personality disorder, obesity, sexual problems and phobias.
Dosage and instructions
Dosage of fluoxetine ranges from 20-80 mg/day in adults and 10-60 mg/day in children and depends on what the medication is being used for. The chart below describes the usual dose for various disorders:
20-40 mg/day. Initial dose is 20 mg/day with weekly increases up to a maximum of 40 mg/day.
20-60 mg/day. Initial dose is 20 mg/day with weekly increases as needed. Can use 80 mg/day, but doses over 60 mg/day didn't show any improvement in OCD.
60 mg/day. It may be necessary to begin at a lower dose and titrate up to 60 mg/day.
20 mg/day. No improvement is seen with higher doses.
The dose of fluoxetine may need to be decreased in elderly people and those with liver problems.
An extended release form of fluoxetine is available from Eli Lilly. Prozac Weekly is available in 90 mg tablets and is taken once a week after therapeutic levels have been established with fluoxetine 20 mg/day. The first weekly tablet is taken 7 days after the last daily tablet. Prozac Weekly doesn't provide adequate antidepressant activity for everybody.
It takes several weeks for people to experience the full therapeutic effect of fluoxetine. The elimination half-life (amount of time it takes to metabolize half of the daily dose) is 4-6 days, and the elimination half-life of the metabolite norfluoxetine is 16 days or more. That means that it takes several weeks or months to completely eliminate fluoxetine from your system.
How fluoxetine works
Although the exact cause or causes of depression is unknown, it is increasingly clear that a biochemical imbalance is involved. Several neurotransmitters-dopamine, norepinephrine and serotonin-seem to play a part in anxiety and mood regulation, with serotonin being the most important. Fluoxetine and other SSRI antidepressants block the reabsorption of serotonin by nerve cells in the brain and throughout the body, allowing serotonin to accumulate and re-establishing biochemical balance.
Fluoxetine was one of the earliest SSRI's and is not as "serotonin specific" as newer ones, so it has some effect on dopamine and norepinephrine, too.
Fluoxetine is metabolized in the liver before it is excreted in the feces. When a substance is metabolized, it is broken down into other compounds. Some of these compounds are biologically inactive and are excreted; some are biologically active, and are called "active metabolites." Fluoxetine has one active metabolite, norfluoxetine, that has the same action as the parent compound. This extends the half-life (the amount of time the drug is active in your body) of fluoxetine significantly.
There is considerable genetically determined variability in how rapidly people metabolize fluoxetine. That is why different people need different doses, and is also why Prozac Weekly is not effective for some people-they metabolize the medication too quickly.
Most people who take SSRIs experience mild to moderate side effects initially; those side effects usually get better over time. The most common side effects experienced with fluoxetine are:
- Restlessness and anxiety
- Flu-like syndrome
- Digestive problems-dry mouth, loss of appetite, nausea, flatulence, heartburn, diarrhea or constipation
- Sleep problems-somnolence or insomnia
- Rash or hives
- Tremor or seizures
- Sexual side effects
For more information about serious side effects, see the section on Warnings and Precautions.
Fluoxetine interacts with many medications, especially those that are metabolized in the liver and those that have an effect on serotonin.
Some of the medications that interact with fluoxetine are:
- Tricyclic antidepressants
- Antipsychotic medications-thioridazine (Mellaril) should not be taken concurrently with fluoxetine because there is a risk of developing life-threatening heart dysrhythmias.
- Antiarrhythmic medications
- Anticonvulsive medications
- Benzodiazepines (a type of antianxiety medication)
- Aspirin, non-steroidal anti-inflammatory medications
- Serotonergic medications (medications that affect serotonin)-these can cause serotonin syndrome
- MAOI (monamine oxidase inhibitor), other SSRI and SNRI (serotonin-norepinephrine reuptake inhibitor) antidepressants
- Triptans (medications for migraine headache)
- St. John's Wort, valerian, kava kava
- Tramadol (a pain medication)
- Cocaine, Ecstasy and other recreational drugs
Abrupt discontinuation of SSRIs can cause unpleasant withdrawal symptoms. Because fluoxetine lasts so long in the body, withdrawal symptoms may not be as severe as with other SSRI's, but they can still occur and the dose should be gradually tapered before stopping the medication. Symptoms of fluoxetine withdrawal include:
- Mood instability
- Irritability, agitation, anxiety
- Sensations of electrical shock
- Headache, lethargy or insomnia
Warnings, precautions and contraindications
Increased risk of suicide: Recent studies suggest that there is an increased risk of suicide in the early weeks of therapy. Although this phenomenon was initially observed in children and an FDA warning was mandated related to the use of antidepressants in children, further observations have caused the warning to be extended to adolescents and young adults. All people who start taking fluoxetine, regardless of age, should be monitored closely for the first several weeks. This includes:
- At least weekly face-to-face appointments with a physician or therapist
- At least daily monitoring by family or friends
- Eliciting (asking about) information about thoughts of suicide or self-harm
- Observation by self and others for agitation, mood changes, restlessness, unusual thoughts and other symptoms.
There is some concern that a small percentage of individuals are at risk for paranoia and violence rather than suicide. Any alterations in thought processes, mood or anxiety must be reported to the physician immediately.
Serotonin Syndrome: Serotonin syndrome is a toxicity syndrome that occurs in SSRI overdose or when more than one serotonergic medication is taken. Because many, many medications affect serotonin, it is important to make sure your doctor and pharmacist know about all medications, over the counter medications, natural remedies, recreational drugs, herbal teas, nutritional supplements and vitamins you take.
The symptoms of serotonin syndrome begin abruptly and dramatically minutes or hours after the offending medication is taken. The early symptoms are shivering, anxiety, rapid heart rate, tremors and twitches and anxiety. Symptoms may progress to fever, high blood pressure, sweating, muscle contractions and agitation. In severe serotonin syndrome, there may be cardiovascular collapse and shock, fever over 104°F, muscle rigidity, seizures, hallucinations, coma, multiple organ failure and death.
Allergies: Allergic reactions to fluoxetine are rare but do occur. Rashes, hives and anaphylaxis have been observed.
Vasculitis: On rare occasions people have developed a lupus-like vasculitis. This syndrome usually begins with a rash and progresses to involve the lungs, kidneys and liver. It can result in organ failure and death.
Post SSRI Sexual Dysfunction: Transient sexual dysfunction is common in both men and women after starting fluoxetine. Usually it resolves after taking the medication for a few weeks; occasionally it may be necessary to discontinue fluoxetine, and symptoms resolve within a few weeks of discontinuation. Occasionally, however, sexual dysfunction may persist for months or years or may never resolve. The sexual side effects most often seen are decreased libido, female anorgasmia and ejaculatory dysfunction.
Pregnancy: SSRIs, including fluoxetine, are contraindicated in women who are pregnant or who wish to become pregnant. They are associated with cardiac birth defects and pulmonary hypertension of the newborn.blog comments powered by Disqus