Prozac (Fluoxetine) Oral: Uses, Side Effects, Dosages - Verywell Health
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What Is Prozac?
Prozac (fluoxetine) is an oral drug used to treat depression, obsessive-compulsive disorder, panic disorder, and other psychiatric conditions.
Prozac belongs to a group of drugs known as selective serotonin reuptake inhibitors (SSRIs). These drugs affect the way the neurons in your brain receive certain signaling molecules, called neurotransmitters.
Serotonin is an essential signaling molecule in your brain that plays a role in regulating mood. In depression and some related conditions, a person might not be getting enough serotonin inside certain neurons in the brain. Among its other effects, an SSRI drug like Prozac blocks the "reuptake" of serotonin, allowing it to increase serotonin activity in the brain.
Antidepressants like Prozac can increase the risk of suicidal thinking and behavior in children, adolescents, and young adults with major depressive disorder. The Food and Drug Administration (FDA) has issued a warning about this risk. People of all ages who are taking Prozac should be monitored closely for worsening symptoms and suicidal thoughts or behaviors.
Drug Facts
Generic Name: Fluoxetine
Brand Name(s): Prozac, Rapiflux, Sarafem, Selfemra
Drug Availability: Prescription
Therapeutic Classification: Antidepressant
Available Generically: Yes
Controlled Substance: N/A
Administration Route: Oral
Active Ingredient: Fluoxetine
Dosage Form(s): Tablet, capsule, syrup, solution
What Is Prozac Used For?
The FDA approved Prozac to treat the following mental health disorders:
Prozac is approved for major depressive disorder, which involves severe and long-lasting changes in your mood and other symptoms, like changes in sleep and appetite.
The FDA also approved Prozac for use with another medication, Zyprexa, to treat:
- "Treatment-resistant" depression, in which a person hasn't had good responses to multiple types of treatment
- Bipolar I disorder (sometimes called "manic depression")
For the above conditions, taking Prozac on its own may increase the risk that a person will experience manic symptoms. Taking Prozac with Zyprexa, a mood-stabilizing drug, helps lower that risk in people with bipolar disorder.
Verywell / Dennis Madamba
How to Take Prozac
Prozac is available as oral tablets, capsules, and in a liquid form. You can take this medication with or without food. If you are taking the oral liquid, make sure you shake the bottle well before each use and use a marked measuring spoon, oral syringe, or medicine cup to measure your dose.
Storage
You should store Prozac at room temperature and keep it away from light. For this and for all other medications, store safely away from young children.
Off-Label Uses
Healthcare providers sometimes prescribe Prozac off-label for use in other medical conditions that are not listed on the FDA label.
Although not a complete list, Prozac is sometimes used off-label for:³
- Anorexia
- Premature ejaculation
- Other types of anxiety disorders
How Long Does Prozac Take to Work?
It could take four to five weeks before you start to feel the full effect of taking Prozac. Don't stop taking it if you don't notice improvement right away.
What Are the Side Effects of Prozac?
This is not a complete list of side effects, and others may occur. A medical professional can advise you on side effects. If you experience other effects, contact your pharmacist or a medical professional. You may report side effects to the FDA at www.fda.gov/medwatch or 1-800-FDA-1088.
Many people notice no negative side effects at all from taking Prozac. However, some people do experience problems while taking the medication.
Common Side Effects
Potential side effects of Prozac can include:
- Nausea
- Headache
- Fatigue
- Increased sweating
- Changes in appetite
- Diarrhea or constipation
- Insomnia
- Sexual dysfunction
Severe Side Effects
For some severe side effects, you will need to stop taking Prozac, at least for a while. Your healthcare provider will help develop a plan.
Serotonin Syndrome
Serotonin syndrome is one of the potentially serious problems associated with this medication. It can sometimes happen from taking Prozac as prescribed, but it is more likely to occur if someone has overdosed. It is also more likely to occur if a person takes both Prozac and another drug that can affect the serotonin in your brain.
Symptoms from serotonin syndrome are usually mild, but can sometimes be severe. Severe symptoms can include:
- Fever
- High blood pressure
- Muscle rigidity
- Disorientation and delirium
- Seizures
- Kidney failure
- Respiratory failure
If you notice any problems, like unusual fever, call your healthcare provider. For potentially life-threatening symptoms, like seizure or difficulty breathing, call 911.
Suicide and Worsening Symptoms
Similar to other SSRIs, Prozac can increase the risk of initially worsening depressive symptoms. A small percentage of people may experience problems such as thinking about suicide. This risk may be greater for young people who start taking Prozac.
Because of this risk, it's important to monitor a person who first starts taking the drug or changes their dose.
If you experience any of these symptoms, contact your mental healthcare provider right away. If you are having suicidal thoughts, call 911 or a suicide prevention hotline.
Triggering Mania in Bipolar Depression
Hypomania causes problems like difficulty sleeping, uncomfortably fast thinking, and increased risk-taking. It can happen in someone who has a bipolar pattern of depression that hasn't yet been diagnosed. Prozac shouldn't be prescribed for someone with known bipolar depression.
If you experience manic symptoms after starting Prozac, contact your mental healthcare provider right away.
Dosage: How Much Prozac Should I Take?
The dose of this medicine 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 this medicine. 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.
- For 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.
- For 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.
- For obsessive-compulsive disorder:
- 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.
- 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.
- For panic disorder:
- Adults—At first, 10 milligrams (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—Use and dose must be determined by your doctor.
- For premenstrual dysphoric disorder:
- 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.
- For bulimia nervosa:
Modification
Older adults and patients with liver impairment may require a lower or less frequent dosage.
Prozac is sometimes used in combination with another antipsychotic medication called Zyprexa (olanzapine).
A starting dose of oral olanzapine 2.5 to 5 milligrams (mg) with 20 mg of Prozac should be used in people with:
- Predisposition to hypotensive (low blood pressure) reactions
- Liver impairment
- A combination of certain factors that may slow drug metabolism (female sex, geriatric age, non-smoking status)
- Sensitivity to olanzapine
People who have a combination of factors that slow the metabolism of olanzapine and Prozac may require dosage adjustments.
Missed Dose
If you miss a dose, take it as soon as you think about it. If it is close to the time of your next dose, do not double up. Instead, continue to take your medication as prescribed.
Overdose: What Happens If I Take Too Much Prozac?
Potential symptoms of an overdose include seizures, sleepiness, and confusion. People who have overdosed on large amounts are more likely to experience serious symptoms.
What Happens If I Overdose on Prozac?
If you think you or someone else may have overdosed on Prozac (fluoxetine), call a healthcare provider or the Poison Control Center (800-222-1222).
If someone collapses or isn't breathing after taking fluoxetine, call 911 immediately.
Precautions
It is important that your doctor check your progress at regular visits, to make sure this medicine is working properly. Blood tests may be needed to check for unwanted effects.
Do not take fluoxetine with a monoamine oxidase (MAO) inhibitor (eg, isocarboxazid [Marplan®], linezolid [Zyvox®], methylene blue injection, phenelzine [Nardil®], selegiline [Eldepryl®], tranylcypromine [Parnate®]). Do not start taking fluoxetine during the 2 weeks after you stop a MAO inhibitor and wait 5 weeks after stopping fluoxetine before you start taking a MAO inhibitor. If you take them together or do not wait the proper amount of time, you may develop confusion, agitation, restlessness, stomach or intestinal symptoms, a sudden high body temperature, an extremely high blood pressure, or severe convulsions.
Do not take thioridazine (Mellaril®) with fluoxetine and wait 5 weeks after stopping fluoxetine before you start taking thioridazine. Do not use pimozide (Orap®) with fluoxetine. Using these medicines together can cause very serious heart problems.
Fluoxetine may cause a serious condition called serotonin syndrome if taken together with some medicines. Do not use fluoxetine with buspirone (Buspar®), fentanyl (Abstral®, Duragesic®), lithium (Eskalith®, Lithobid®), tryptophan, St. John's wort, amphetamines, or some pain or migraine medicines (eg, rizatriptan, sumatriptan, tramadol, Frova®, Imitrex®, Maxalt®, Relpax®, Ultram®, Zomig®). Check with your doctor first before taking any other medicines with fluoxetine.
Fluoxetine may cause some teenagers and young adults to be agitated, irritable, or display other abnormal behaviors. It may also cause some people to have suicidal thoughts and tendencies or to become more depressed. Some people may have trouble sleeping, get upset easily, have a big increase in energy, or start to act reckless. If you or your caregiver notice any of these unwanted effects, tell your doctor right away. Let the doctor know if you or anyone in your family has bipolar disorder (manic-depressive) or has tried to commit suicide.
Do not suddenly stop taking this medicine without checking first with your doctor. Your doctor may want you to gradually reduce the amount you are using before stopping it completely. This will decrease the chance of having withdrawal symptoms such as agitation, breathing problems, chest pain, confusion, diarrhea, dizziness or lightheadedness, fast heartbeat, headache, increased sweating, muscle pain, nausea, restlessness, runny nose, trouble sleeping, trembling or shaking, unusual tiredness or weakness, vision changes, or vomiting.
Tell your doctor right away if you develop a rash or hives, swelling of the face, eyes, or mouth, or trouble breathing after taking this medicine.
This medicine may increase your risk for bleeding problems. Make sure your doctor knows if you are also taking other medicines that thin the blood, such as aspirin, nonsteroidal antiinflammatory agents, also called NSAIDs (eg, diclofenac, ibuprofen, naproxen, Advil®, Aleve®, Celebrex®, Voltaren®), or warfarin (Coumadin®, Jantoven®).
Hyponatremia (low sodium in the blood) may occur with this medicine. Check with your doctor right away if you have confusion, difficulty concentrating, headaches, memory problems, weakness, and unsteadiness.
Contact your doctor right away if you have dizziness, fainting, or a fast, pounding, or uneven heartbeat. Make sure your doctor knows if you have ever had a heart rhythm problem, such as QT prolongation, or if you or a family member has had a heart attack, heart failure, low blood pressure, or a stroke.
The use of alcohol is not recommended in patients who are taking fluoxetine.
This medicine may affect blood sugar levels. If you are diabetic and notice a change in the results of your blood or urine sugar tests, check with your doctor.
This medicine may cause some people to become drowsy or less able to think clearly, or to have poor muscle control. Make sure you know how you react to fluoxetine before you drive, use machines, or do anything else that could be dangerous if you are not alert and well able to control your movements.
Check with your doctor right away if you have decreased interest in sexual intercourse, delayed or inability to have an orgasm in women, inability to have or keep an erection in men, or loss in sexual ability, desire, drive, or performance. These could be symptoms of sexual dysfunction.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal (eg, St. John's wort) or vitamin supplements.
What Are Reasons I Shouldn't Take Prozac?
If you are pregnant or thinking of getting pregnant, you should talk with your healthcare provider about whether Prozac is the right choice for you. Prozac may increase the risk that your baby will have certain problems, like heart malformation.
However, the real risks of taking Prozac while pregnant are not completely clear. People who have been taking Prozac may experience problems like a recurrence of their depression. Talk with your healthcare provider about the potential risks and benefits of Prozac in your situation.
Do not stop taking Prozac abruptly if you find out you are pregnant. Instead, call your medical provider and make a plan for stopping Prozac.
Prozac also isn't generally recommended for people who are breastfeeding. But if you are struggling with your mental health, you should contact your provider to explore your options.
Prozac should be used with caution in:
- Older adults: Prozac can cause a higher risk of certain complications, like low sodium levels in the blood (hyponatremia). You should weigh the risks and benefits with your doctor.
- People with certain heart conditions: There is a risk that Prozac might trigger abnormal heart rhythms.
- People with bipolar type depression: Your healthcare provider should ask you questions about your medical history and symptoms to make sure the risks of taking Prozac are low.
- People with an allergy or hypersensitivity to the medication
What Other Medications Interact With Prozac?
You should never take Prozac along with other medications known as monoamine oxidase inhibitors (MAOIs). MAOIs are sometimes given to treat depression. Taking both types of medications can lead to a serious problem known as serotonin syndrome.
MAOI drugs are not prescribed as frequently as they used to be. The better side effect profile of Prozac and other related drugs has made the use of MAOIs less common, but some people still need them.
Examples of MAOI drugs include:
- Marplan (isocarboxazid)
- Zyvox (linezolid)
- Nardil (phenelzine)
Other drugs can increase the risk of serotonin syndrome when used along with Prozac, including:
- Certain drugs used for migraines: "Triptan" drugs like Imitrex (sumatriptan)
- Certain pain-relieving drugs, like Ultram (tramadol)
- Some drugs used for anxiety, like Buspar (buspirone)
- Drugs used for bipolar depression, such as lithium
- Certain antibiotics, especially Zyvox
- Some over-the-counter holistic health products like St. John's Wort
This is not a complete list of the drugs that might trigger serotonin syndrome or cause other problems in someone already taking Prozac. Prozac might affect how your body processes certain drugs, which might lead to different issues.
It doesn't necessarily mean that you wouldn't be able to take these medications if needed. But you should be aware of this potential issue and discuss your full medication list with your medical provider.
What Medications Are Similar?
For financial reasons, the drug company that first developed Prozac went on to repackage the drug in a slightly different form, called Sarafem. Although it is not completely chemically identical to the active ingredient in Prozac, it works in exactly the same way.
The FDA approved Sarafem for severe mood changes that affect some people just before and during their period (premenstrual dysphoric disorder).
Several other SSRI medications are currently available, including:
These drugs are all similar to Prozac in terms of their potential benefits and risk of side effects. You might do better with one than the other, but they are likely to affect you similarly.
Depending on your situation, another category of treatment might make more sense. A very closely related group of medications is called serotonin noradrenaline reuptake inhibitors (SNRIs). These drugs affect not only serotonin, but a different neurotransmitter called noradrenaline.
SNRIs can treat many of the same conditions as SSRIs, such as anxiety.⁵ But they also might work particularly well for people with other medical problems. For example, the SNRI known as Cymbalta (duloxetine) might be helpful if you are dealing with both depression and chronic pain.⁸ Effexor (venlafaxine) is another commonly prescribed drug in this group.
Please note, all of these drugs discussed are not intended to be taken along with Prozac. Ask your healthcare provider if you are unsure if a drug you are taking can safely be used at the same time as Prozac.
How Can I Stay Healthy While Taking Prozac?
Like many drugs, Prozac comes with a long list of potential side effects, which can be intimidating. However, for many people, it is a very safe drug. And for some, it has truly life-changing positive effects.
Unfortunately, there is still some stigma around mental health issues and treatments like Prozac. But don't let that stop you from getting what works for you.
Before starting Prozac, talk through all your options—including non-pharmaceutical treatment—with your healthcare provider. When you start, educate yourself on potential risks, such as potential problems from combining certain medications. That will help you feel informed and empowered to make good decisions for yourself.
Medical Disclaimer
Verywell Health's drug information is meant for education purposes only and not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare professional. Consult your doctor before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.
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