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Prozac: What Is It? Uses, Side Effects, and Dosage

An estimated 17.3 million American adults, or about 7.1 percent of the population, experience a major depressive episode lasting two or more weeks each year. Prozac is a widely recognized drug that may offer hope of symptom relief for people who are suffering from a major depressive episode or other types of mental health conditions. Since entering the market in the mid-1980s, Prozac has rapidly become one of the most popular drugs in the United States and has spawned the evolution of an entire class of new medications.


Also known under the generic name fluoxetine, Prozac was the first medication introduced in the class of antidepressant medications known as selective serotonin reuptake inhibitors (SSRIs). SSRIs are commonly used to treat depression and anxiety today and are one of the most popularly prescribed classes of drugs in the United States, but all of this has happened in the past 35 years.  Prozac, which is often the first name that comes to mind when people think of antidepressant medications, was first introduced to the market in 1986. Approximately 22 million prescriptions were written for Prozac in 2017, making it the most well known and one of the most popular SSRIs on the market.

Conditions Treated

While Prozac was first approved to treat clinical depression in 1986, it has since been approved for the treatment of many other mental health conditions, including major depressive disorder (MDD), obsessive-compulsive disorder (OCD), panic disorder, bulimia nervosa, and premenstrual dysphoric disorder (PMDD). Each of these conditions and their associated symptoms is described below.

Clinical Depression/Major Depressive Disorder
Clinical depression, a term used interchangeably with major depressive disorder, is characterized by persistent and intense feelings of sadness that last for extended periods of time - at least two weeks or more. Depression has mental manifestations that impact your behavior and mood, but it can also cause physical issues as well, including loss of appetite and changes in sleep. People who experience major depressive disorder may have trouble performing everyday activities, such as showering or eating or lose interest in doing activities that they once enjoyed, and they may have suicidal thoughts and tendencies. About seven percent of American adults have an episode of clinical depression each year, making it one of the most common mental health issues in the U.S. Symptoms of major depressive disorder include:

  • Feelings of worthlessness, guilt, hopelessness, or helplessness
  • Feeling sad, empty, or tearful
  • Difficulty concentrating and low energy
  • Lost of interest in activities you used to enjoy
  • Feelings of moving or thinking in slow motion
  • Sleeping and eating more or less than usual
  • Nervous energy
  • Suicidal thoughts or behaviors
  • Obsessive-Compulsive Disorder

Obsessive-compulsive disorder, also known as OCD, is diagnosed as a result of the presence of two characteristics: obsessive, worrisome thoughts that cause anxiety, such as the loss of a loved one,  and compulsions, or behaviors that are performed to relieve the anxious thoughts. People with OCD feel compelled to perform certain rituals repeatedly, even when they do not want to or when it is inconvenient. Compulsive behaviors may include things such as locking and unlocking the door or repeated hand washing. Obsessive-compulsive disorder typically develops in childhood or early adulthood and intensifies later in life. Symptoms include:

  • Anxiety about germs and dirt
  • Need for symmetry and order, including obsessive cleanliness
  • Fear of contamination
  • Difficulty throwing away things of little to no value (hoarding tendencies)
  • Feeling that you can protect other people by performing certain behaviors or rituals
  • Disturbing thoughts 
  • People with obsessive-compulsive disorder may exhibit some of the following behaviors:
  • Hoarding unnecessary possessions of little value
  • Excessive hand washing, showering, or repetitive cleaning
  • Checking things over and over again, such as making sure the door is locked
  • Rearranging things continuously to get them “just right”

Panic Disorder
Panic disorder is one of the eight types of anxiety disorders and is characterized by unexpected and repeated episodes of intense fear, called panic attacks, that cause physical symptoms. Physical symptoms associated with panic disorder include chest pain, shortness of breath, heart palpitations, sweating, dizziness, and nausea.
Bulimia Nervosa
Bulimia nervosa is an eating disorder characterized by a binging on food (eating an unusually large quantity of food, typically in a very short amount of time, past the point of fullness) and then using certain methods to purge the food in order to prevent weight gain. Purging behaviors may include laxative abuse, induced vomiting, or excessive exercise to prevent weight gain.
Premenstrual Dysphoric Disorder
Premenstrual dysphoric disorder (PMDD) is experienced by about five percent of women worldwide and is characterized by heightened experiences of depression, tension, and irritability for several days prior to menstruation. Although some of these symptoms are common in women prior to their periods, PMDD is characterized by extreme manifestations of these symptoms. 

How Prozac Works

Selective serotonin reuptake inhibitors (SSRIs), the class of drugs to which Prozac belongs, work by blocking the absorption of serotonin, a neurotransmitter, in the brain. This action helps regulate the amount of serotonin in the brain, which helps brain cells transmit messages to each other, helping to improve and stabilize the mood. Additionally, the medication also activates neurons in the hippocampus, a portion of the brain that is responsible for forming memories. When taking Prozac, people who suffer from depression may experience an improved mood, regain interest in old hobbies that they once enjoyed, and feel the physical symptoms of depression, such as exhaustion and loss of appetite, ease. The other conditions treated by Prozac also benefit from the mood-stabilizing effects of the medication.


Like most medications, the brand name form of Prozac is substantially more expensive than the generic form of the drug, fluoxetine. While fluoxetine is typically covered by most Medicare and insurance plans, it may be possible to receive a cheaper price on the drug by using a pharmacy discount card or coupon or paying the cash price. The following table compares the costs of a 30 day supply of Prozac and fluoxetine.

Costs of a 30-Day Supply of Prozac and Fluoxetine

10 mg oral capsules
20 mg oral capsules
40 mg oral capsules

Because there are many different manufacturers for fluoxetine, the prices of the drug are extremely affordable even for those who are uninsured or underinsured. Although some people express concern over the quality of generic drugs, these concerns are unfounded; the Food and Drug Administration (FDA) subjects generic forms of the medication to the same stringent testing and clinical trials as the brand name form of the drug. The generic medication uses the same active ingredient as the brand name form of the medication in the same amount but may use different inactive ingredients that affect the color, size, shape, or taste of the medication. However, you will receive the same treatment when using a generic medication of the same form and strength as you would with a brand name medication. Also, make sure to store any medication at room temperature and to read the full drug information or any black box warnings on the bottle. 


Since the introduction of Prozac as the first SSRI in 1986, many new SSRIs have also been developed for the treatment of mental health conditions. Nonetheless, Prozac remains a favorite of many prescribers and patients due to the many benefits offered by the drug. Benefits associated with the use of Prozac include:

  • Increased energy. Prozac is considered more energizing than other antidepressants, so it may help people with naturally low energy levels, or those who are experiencing low energy due to severe depression, to regain some of their energy. 
  • Prozac may only be one medication, but it has been proven effective at treating numerous mental health conditions, including major depressive disorder, obsessive-compulsive disorder, panic disorder, bulimia nervosa, and premenstrual dysphoric disorder. It is not uncommon for people to suffer from several types of mental health issues at once (such as a person with bulimia nervosa who is also depressed), so individuals suffering from several of these conditions may find relief with the use of Prozac alone.
  • Prozac is not likely to have side effects on the heart and heart rate, which means it is considered safer to use in older adults compared to some other types of antidepressants. 
  • Some patients find that they lose weight while taking Prozac due to Increased energy levels which can be helpful for people who are overweight.
  • Children with major depressive disorder or obsessive-compulsive disorder can be safely treated with Prozac.


Your doctor will determine the appropriate dose of Prozac for you based on your age and the purpose of treatment, but your medication dose may have to be adjusted several times before you get it just right. The standard treatment for adults suffering from major depressive disorder starts at 20 mg per day, taken in the morning. Doctors may increase your dose by 20 mg every few weeks as needed, but the standard dose is between 20 and 60 mg per day. The maximum recommended dose of Prozac is 80 mg per day. Prozac weekly is a version that is available in a delayed-release oral capsule that is taken weekly. When taking the delayed-release oral capsule, patients will take a 90 mg capsule once per week. The effects of Prozac are normally experienced in about four weeks.

Patients who take Prozac should not abruptly stop or change their dose without consulting their doctor for medical advice, as this can cause withdrawal symptoms and other adverse effects if a patient has been using the medication for six weeks or more. Symptoms of withdrawal or a missed dose include:

  • Dizziness
  • Confusion
  • Nightmares and insomnia
  • Vertigo
  • Nausea
  • Tremors
  • Gastrointestinal issues (diarrhea, indigestion, nausea)
  • Flu-like symptoms
  • Anxiety
  • Agitation
  • Irritability
  • Aggression

Side Effects
Side effects associated with Prozac generally fall into two categories: common and rare/serious. Common side effects associated with Prozac include:

  • Headache
  • Nausea
  • Diarrhea
  • Dry Mouth or sore throat 
  • Increased sweating
  • Feeling nervous
  • Increased bruising or minor skin rashes
  • Restlessness
  • Fatigue
  • Weight loss
  • Drowsiness and tiredness
  • Difficulty sleeping (insomnia)
  • Decreased libido or sex drive
  • Sexual dysfunction, such as difficulty with orgasm or ejaculatory delay

Rare but serious side effects associated with Prozac include:
Low sodium blood levels, as evidenced by:

  • Headache
  • Weakness
  • Difficulty concentrating
  • Difficulty remembering
  • Teeth grinding
  • Angle-closure glaucoma, as evidenced by:
  • Eye pain
  • Changes in vision
  • Swelling or redness in or around the eye
  • Serotonin syndrome, as evidenced by:
  • Shivering
  • Diarrhea
  • Confusion
  • Severe muscular tightness
  • Fever
  • Seizures
  • Death
  • QT prolongation and ventricular arrhythmia including changes in the electrical activity of your heart

Of the risks associated with taking Prozac, the most significant is the increased risk of suicidal thinking, ideation, and behavior in children, adolescents, and young adults suffering from major depressive disorder; however, most antidepressants carry this same risk. Patients with a diagnosis of major depressive disorder should be closely monitored by their health care provider while taking Prozac, especially if they are under the age of 24. If you have any of these concerning reactions, you should not take the next dose without consulting with your doctor. 

Prozac has the potential for serious drug interactions or allergic reactions and should not be taken in conjunction with monoamine oxidase inhibitors (MAOs), especially Pimozide and Thioridazine. Prozac should also not be taken with drugs metabolized by CYP2D6 or with tricyclic antidepressants (TCAs). Patients and prescribers should exercise care when using the drug in conjunction with benzodiazepines and other drugs that affect the central nervous system, such as Ativan and Klonopin. When combined with over-the-counter non-steroidal anti-inflammatories (NSAIDs) like ibuprofen, blood thinners, or other drugs that affect blood pressure and coagulation, Prozac can lead to an increased risk of bleeding. Additionally, Prozac should not be used with antipsychotic drugs or other SSRIs or herbs that are serotonergic. Prozac has been reported to activate mania in people considered susceptible to the condition.

Deciding to Take Prozac

People who take certain types of drugs known to cause dangerous interactions with Prozac, including monoamine oxidase inhibitors (MAOs), especially Pimozide and Thioridazine, drugs metabolized by CYP2D6, with tricyclic antidepressants (TCAs), benzodiazepines, NSAIDs, blood thinners, and antipsychotic drugs or other SSRIs should not take Prozac. People who are allergic to Prozac or its active ingredient, fluoxetine, should not take the medication.

People with certain personal medical histories or family medical histories should use caution when considering taking Prozac. Be sure to give your doctor a complete medical history, especially including any personal or family history examples of the following conditions:

  • Bipolar disorder or manic-depressive disorder
  • Personal or family history of suicide attempts
  • Liver problems
  • Diabetes
  • Low sodium in the blood
  • Severe loss of body water/dehydration
  • Seizures
  • Stomach/intestinal ulcers
  • Glaucoma (angle-closure type)

Older adults are more likely to experience side effects, including an increased risk of bleeding and loss of coordination; loss of coordination increases the risk of falling. Older adults are also considered to be at increased risk of developing low blood sodium. 

Precautions for Pregnant and Nursing Women

Prozac is not considered safe for pregnant women and should only be taken during pregnancy if the potential benefits outweigh the potential for risks to the fetus. Prozac has been found to increase the risk of neonatal maladaptation syndrome, which includes symptoms of jitteriness, problems with feeding and breathing, and hypoglycemia (low blood sugar) in newborns. 
Because Prozac can be passed into breast milk, use by nursing mothers is not advised.

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