Prozac is a brand-name prescription drug approved by the Food and Drug Administration (FDA) to treat major depressive disorder (MDD), obsessive-compulsive disorder (OCD), panic disorder, and binging-purging in people with bulimia. Prozac is also combined with an antipsychotic medication, olanzapine, in people experiencing depressive episodes due to bipolar disorder or with treatment-resistant depression.
Fluoxetine hydrochloride, the active ingredient in Prozac, belongs to a class of drugs called selective serotonin reuptake inhibitors, or SRIs. These drugs work by increasing a chemical in the brain that allows for more efficient nerve activity, allowing people to better manage mood and impulses. Prozac is taken as a capsule by mouth once daily.
Prozac dosage, forms, and strengths
Prozac capsules are taken in one of three dose strengths.
- Capsules: 20 milligrams (mg), 30 mg, 40 mg, and a delayed-release 90 mg form
Prozac dosage for adults
No matter what the diagnosis, Prozac is usually started at a low dose, around 20 mg daily, and gradually titrated (increased) over several weeks until the smallest effective dose is reached.
|Prozac dosage chart|
|Indication||Starting dosage||Standard dosage||Maximum dosage|
|Major depressive disorder||20 mg taken once daily in the morning||20–80 mg taken once daily in the morning||80 mg per day|
|Obsessive-compulsive disorder||20 mg taken once daily in the morning||20–60 mg taken once daily in the morning||80 mg per day|
|Bulimia nervosa||60 mg taken once daily in the morning (starting dose may be lower in some patients)||60 mg taken once daily in the morning||Not specified|
|Panic disorder||10 mg taken once daily in the morning||20 mg taken once daily in the morning||60 mg per day|
|Depressive episodes associated with bipolar I disorder (taken with olanzapine)||20 mg taken once daily in the evening||20–50 mg taken once daily in the evening||50 mg per day|
|Treatment-resistant depression (taken with olanzapine)||20 mg taken once daily in the evening||20–50 mg taken once daily in the evening||50 mg per day|
In addition to the conditions approved by the FDA, Prozac is often used off-label (without FDA approval) to treat premenstrual dysphoric disorder (PMDD) and cataplexy (sudden loss of muscle tone in people with narcolepsy). Dosages are identical to those for major depressive disorder, 20–60 mg taken once daily in the morning with a starting dose of 20 mg a day.
Prozac dosage for major depressive disorder
Major depressive disorder occurs when symptoms of depression persist for longer than two weeks. Prozac is a well-known antidepressant used to relieve depression symptoms. Treatment-resistant depression occurs when treatment does not relieve symptoms or depressive symptoms keep returning. In those cases, treatment can consist of combining Prozac with the antipsychotic medication, olanzapine.
- Standard adult dosage for major depressive disorder: 20–80 mg taken once daily in the morning
- Maximum adult dosage for major depressive disorder: 80 mg per day
- Standard adult dosage for treatment-resistant depression: 20–50 mg taken with 5–20 mg of olanzapine once daily in the evening
- Maximum adult dosage for treatment-resistant depression: 50 mg per day
Prozac dosage for obsessive-compulsive disorder
Obsessive-compulsive disorder (OCD) is characterized by unwanted and intrusive thoughts (obsessions) coupled with strong impulses to repeatedly act on those thoughts. Prozac is a first-line OCD treatment for reducing both OCD symptoms and any related depression symptoms.
- Standard adult dosage for obsessive-compulsive disorder: 20–60 mg taken once daily in the morning
- Maximum adult dosage for obsessive-compulsive disorder: 80 mg per day
Prozac dosage for bulimia nervosa
Bulimia nervosa is a mental health condition in which a negative body image drives a compulsive need to lose weight. In contrast to a similar condition, anorexia, the defining symptoms of bulimia are binge eating followed by purging, fasting, depression, and anxiety. Prozac reduces the incidence of binge eating and purging in bulimia patients. In clinical studies, however, it was shown to be effective only at a 60 mg daily dose.
- Standard adult dosage for bulimia nervosa: 60 mg taken once daily in the morning
- Maximum adult dosage for bulimia nervosa: not specified
Prozac dosage for panic disorder
Panic disorder is a type of anxiety disorder in which people experience sudden, overwhelming panic for no appropriate reason. While many people experience such “panic attacks,” these occurrences rise to the level of panic disorder when they happen frequently, causing people to worry about panic attacks and significantly altering their life to avoid them. Prozac treatment can reduce the incidence and severity of panic attacks as well as reduce the general anxiety associated with panic disorder.
- Standard adult dosage for panic disorder: 20–50 mg taken once daily in the morning
- Maximum adult dosage for panic disorder: 80 mg per day
Prozac dosage for bipolar disorder
Bipolar I disorder is a condition in which people cycle slowly between periods of extreme emotional highs (manic phases) and emotional lows (depressive phases). In people with bipolar I disorder, Prozac is used along with the antipsychotic olanzapine to relieve bipolar I depressive phases.
- Standard adult dosage for bipolar I disorder: 20–50 mg taken with 5–12.5 mg of olanzapine once daily in the evening
- Maximum adult dosage for bipolar I disorder: 50 mg per day
Prozac dosage for children
Prozac is prescribed to children as young as 6 years of age to treat major depressive disorder, obsessive-compulsive disorder, and, combined with olanzapine, depressive phases of bipolar I disorder. A healthcare provider may use Prozac off-label to treat bulimia nervosa, generalized anxiety disorder, social anxiety disorder, post-traumatic stress disorder (PTSD), insomnia, and cataplexy in children.
Major depressive disorder
- Standard dosage in children ages 6–7: 10 mg taken once per day
- Maximum dosage in children ages 6–7: 30 mg per day
- Standard dosage in children ages 8–18: 10–20 mg taken once per day
- Maximum dosage in children ages 8–18: Not defined
- Standard dosage in children ages 7–17: 20–60 mg taken once per day
- Maximum dosage in children ages 7–17: Not defined
Bipolar I disorder acute depressive episode
- Standard Prozac dosage in children ages 10–18: 20–50 mg taken once per day in the evening
- Maximum Prozac dosage in children ages 10–18: 50 mg per day
Prozac dosage for pets
Reconcile is a brand-name fluoxetine tablet approved by the FDA to treat separation anxiety in dogs. However, fluoxetine is frequently and successfully used off-label in both dogs and cats to treat aggression, anxiety, repetitive and confusing behaviors, and inappropriate defecation or urination. Reconcile is given orally as a chewable tablet. The standard dose for dogs is 1–2 mg per kilogram (kg) of body weight taken once daily and 0.5–1.5 mg/kg of body weight taken once daily for cats.
Prozac dosage restrictions
Among the contraindications, people with hypersensitivity to fluoxetine, the active ingredient in Prozac, will not be prescribed the drug. A lower dose of fluoxetine may be used in people with hepatic impairment (liver problems), but renal impairment (kidney problems) will not affect dosing. Dialysis will not require a supplement.
How to take Prozac
Prozac is taken as a capsule once daily with or without food.
- Take this medicine as directed.
- Prozac will come with a medication guide. Please read this medication guide before taking the medicine.
- Swallow the capsule whole with a glass of water.
- It may take several weeks of taking Prozac before symptoms improve. Continue to take the medicine even if it doesn’t seem to work. If there are concerns about Prozac’s effectiveness, talk to the doctor or prescriber.
- Store Prozac at room temperature (59°–86° F) away from light.
Prozac dosage FAQs
How long does it take Prozac to work?
Prozac often improves symptoms after one to two weeks of daily dosing, but it does not reach its full, steady-state concentration in the blood until it’s been taken for four to five weeks.
How long does Prozac stay in your system?
Prozac persists in the body for a long time. Not only does fluoxetine have a long half-life, but it also is converted by the body into a similar drug called norfluoxetine that works just like fluoxetine. With a combined half-life of four to six days for fluoxetine and up to 16 days for norfluoxetine, Prozac remains active in the body for several weeks after the last dose has been taken.
What happens if I miss a dose of Prozac?
If a dose is missed or forgotten, take it as soon as possible. However, if it is almost time for the next dose, wait until then to take the medicine and skip the missed dose. Do not take extra medicine to make up for a missed dose.
How do I stop taking Prozac?
Prozac can cause withdrawal symptoms, so suddenly stopping the medication should be avoided. Called antidepressant discontinuation syndrome, the most common symptoms are nausea, irritability, dizziness, anxiety, nervousness, and headache. Prozac, however, is less likely to cause withdrawal than other antidepressants because it remains active in the body for several weeks after the last dose is taken. Still, doctors and other healthcare professionals are advised to steadily reduce the dose when stopping Prozac.
There are several reasons why people may need to discontinue Prozac. First, the drug may not work the best in certain people. Alternatively, it may cause intolerable side effects like dry mouth, abnormal dreams, or weakness (asthenia). In rare cases, it may cause serious adverse reactions such as suicidal thoughts, worsening depression, serotonin syndrome, glaucoma, heart irregularities (QT interval prolongation), weight loss, sexual dysfunction, or a severe allergic reaction.
In those cases, alternative therapies for depression include other SSRIs, like sertraline, tricyclic antidepressants, serotonin and norepinephrine reuptake inhibitors (SNRIs), and atypical antidepressants.
For anxiety, buspirone, other antidepressants, or benzodiazepines—such as Xanax (alprazolam) or Valium (diazepam)—can help calm anxiety symptoms if Prozac is discontinued. Beta-blockers, normally used to treat heart or blood pressure problems, can help relieve the physical symptoms of anxiety in specific settings.
What interacts with Prozac?
Because of possible dangerous drug interactions, people taking Prozac should not also take the antipsychotics pimozide or thioridazine or take monoamine oxidase inhibitors (MAOIs), a small class of drugs that includes some antidepressant medications (phenelzine, isocarboxazid, tranylcypromine), some antibiotics (linezolid), seizure medications (rasagiline and selegiline), and a commonly-used imaging contrast dye (methylene blue). MAO inhibitors have to be discontinued for at least 14 days before Prozac can be taken.
Serotonin syndrome is a potentially serious side effect when taking drugs like Prozac. Caused by too much serotonin in the brain, serotonin syndrome can range from mild to life-threatening. To prevent serotonin syndrome, Prozac is used with caution with other drugs that raise serotonin levels including other antidepressants, antipsychotics, anxiety medications, lithium, opioid pain relievers, migraine medications, amphetamines, anti-nausea drugs, and some herbal supplements, such as St. John’s wort.
What happens when you mix Prozac and alcohol?
Alcohol can worsen Prozac’s side effects such as drowsiness, dizziness, and sexual dysfunction. It’s a good idea to avoid alcohol when first taking Prozac to gauge the effects of the medication on alertness and coordination.
Is it safe to take Prozac during pregnancy?
Prozac is used cautiously in pregnant women. The risks are unknown, but there have been no reports of an increased risk of miscarriage or birth defects. Fluoxetine is found in breast milk, so nursing mothers are advised to avoid breastfeeding while taking Prozac or switch to a different medication. Mothers who do breastfeed and take Prozac should watch infants carefully for irritability, agitation, or weight gain problems to make sure the drug is not affecting the baby.
- Fluoxetine hydrochloride drug summary, Prescribers Digital Reference
- Practical guideline for the treatment of patients with Major Depressive Disorder, American Psychiatric Society
- Prozac, Epocrates
- Prozac prescribing information, U.S. National Library of Medicine
- Reconcile prescribing information, U.S. National Library of Medicine
- Plumb’s Veterinary Drug Handbook, 7th ed.