By Irfana Parveen

B.Sc (Psychiatry Ward)

03 May 2022
Medically reviewed by
Freny Menezes
Pharm. D
Table of Contents

Depression is a mood disorder which seriously affects your daily day activities by making you very low, insecure and aggressive, which affects your health. Depressive episodes will make you cry, sad and feel hopeless, but remember, everyone will face this situation; this is a part of life.  

But one who is dealing with depression will have sadness, Low self-esteem daily. That should be immediately treated with the help of a doctor. Untreated depression will harm you by leading you to develop suicidal thoughts etc. 

In the US, 1 in 10% Adults face depression, affecting their ability in school, college and the workplace. Moreover, 16.39% of adults reported major depressive disorder in the last year. 

There are several antidepressants available to treat your condition, Like drug Prozac is widely used and a very effective drug to treat major depressive disorder, anxiety and some other states. 
let us see about the drug in more detail, 

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What is Prozac?

Prozac or fluoxetine is a widely prescribed drug in the US for treating antidepressants. More than 28 million Americans are using Prozac. Prozac helps in treating depressive episodes by stimulating certain chemicals in the brain cells.

The food and drug administration approved the drug to treat adults and children with depression. 
Moreover, it helps in your mood, sleep patterns, and appetite and also helps to restore your daily activities. It is widely used in conditions like

  • Major depressive disorder
  • Obsessive-compulsive disorder
  • Migraine headache
  • Fibromyalgia
  • Generalised anxiety disorder
  • Panic disorder
  • Bulimia nervosa

How Does Prozac Work? 

Prozac is an Antidepressant drug belonging to the Selective serotonin Reuptake inhibitors SSRIs that usually work by increasing the level of neurotransmitters. It works by inhibiting the reabsorption in the serotonin level, which is the chemical present in the brain which helps regulate mood, behaviour, digestion, sleep mem, sexual Desire and other functions.

A low level of serotonin will result in depression, and the low level should be treated in affected patients. For this, Prozac will be very effective at treating serotonin levels, which helps manage depression and anxiety. It was the most prescribed drug in the US. It can be used in children over the age of 10. 

How Long Does Prozac Stay In Your System?

Prozac (Fluoxetine) stays in your system for 25 days after an individual stops taking the drug. However, prescription drugs are only 99%out of the system.

If a patient takes Prozac for more than 22 days, specific metabolites are excreted into yourthetem. These secretions will take around 22 to 82 and a half days to be eliminated from your body, depending on other factors.
80% of the drug is excreted through urine.

The Half-life Of Prozac

Half-life refers to the time taken by a drug to reduce the number of active ingredients present in your blood in half. Fluoxetine has a half-life of roughly 2 to 7 days; however, norfluoxetine has a half-life of 4 to 15 days. Fluoxetine remains in the system for approximately 2 to 3 months after the last dose when nor-Fluoxetine is wholly eliminated.
Study On The Half-life Of Fluoxetine:

A study on the pharmacokinetics of Fluoxetine found that Fluoxetine is well absorbed after oral administration, has a high protein binding rate, and has an extensive distribution volume. The half-life of Fluoxetine is 1 to 4 days, while the half-life of its metabolite, norfluoxetine, is 7 to 15 days.

Fluoxetine interacts with several other medications. The blood concentrations of antipsychotics and antidepressants were enhanced when Fluoxetine was given repeatedly.

Another study on the half-life of Fluoxetine and its metabolite norFluoxetine found that the half-lives of Fluoxetine and norfluoxetine were 11–16 hours and 21–29 hours, respectively. Even after a single fluoxetine dose, functionally significant blood concentrations of norfluoxetine were detected at 24 hours. Norfluoxetine accounted for the more substantial percentage of active substances in the bloodstream, as observed in people under steady-state settings. 

Factors That Influence The Stay Of Prozac

The stay of Prozac depends on various factors, such as how long you have been taking it. And how much have you been taking? Other factors that influence the stay of Prozac are,

  • Age
  • Sex
  • Body Mass
  • Genetics
  • Food Intake
  • Hepatic Function
  • Metabolic Rate
  • Urinary PH

The metabolites released when taking Prozac (known as norfluoxetine) will take 22 to 82 days to empty the patient's system.

How Long Does Prozac Take To Work?

The active ingredient, Fluoxetine, is absorbed in the gut after taking the drug. It is metabolised in the liver, where it is converted to norfluoxetine metabolites via demethylation processes.

Fluoxetine's mental health advantages, like those of most antidepressants, do not appear immediately after therapy begins. Some people may show changes as soon as two weeks after starting treatment, but it usually takes 4-6 weeks to manifest the total mental health benefits.

How Long Does Prozac Stay In Hair, Urine, And Blood?

Prozac is not usually standard for urine, hair, or blood tests. On the other hand, special test kits can be used to check for the presence of Prozac in various tissue samples.

Urine: Urine tests from Prozac users have revealed detectable levels up to 96 days after their previous medication. 

Blood: Blood samples from people who had been on Prozac for a long time proved positive for the drug even 96 days after they stopped taking it.

Saliva: There is inadequate evidence defining how long Fluoxetine can be found in the saliva due to a lack of study.

Hair: Fluoxetine is undetectable in hair samples. As a result, the drug in the hair has no detection time.

Dosage Of Prozac

When it comes to dosage, it will differ from one to another according to your condition, so before taking the drug, visit your doctor about your health history. 
Prozac is used in several mental health illnesses, such as some of the dosages are given below,

For treating bulimia nervosa:

Adults: 60 mg once a day in the morning.
Children: it should be determined by your doctor.

For treating Depression:

Adults: At starting, use 20 mg once a day. You may take two capsules per day, but not more than 80 mg per day. 
Children: In children, use less than eight years of age should be determined by your doctor.

For treating Bipolar disorder:

Adults: Take 20mg per day; you should not take more than 50mg daily.
For treating obsessive-compulsive disorder:
Adults: At starting 20 mg once a day, you should not exceed more than 80 mg daily.
Children: It is used in 10 mg daily for children seven years and older. 

For treating panic attacks:

Adults: First, take 10mg per day. Not more than 60 mg per day. 
Children: Consult your doctor. 

Missed Dose:

If you forget to take your medicine, take it as soon as you remember; please Don't repeat the dosage too heavily; it will affect your health and lead to side effects. 

Side Effects Of Prozac 

Some of the side effects turn into adverse effects on your health about using the medication,

Common side effects are

Whole body effects: 

  • Headache
  • weakness
  • fever

Gastrointestinal system:

  • Symptoms of Nausea
  • diarrhoea
  • Dry mouth
  • loss of appetite 
  • constipation
  • indigestion

Metabolic Rate 

  • Weight loss appears in rare cases.

Central Nervous System 

  • Feg of  nervousness
  • anxiety
  • dizziness
  • low sexual interest 
  • abnormal thinking

Skin changes

  • increased sweating
  • rash 
  • itching.

Some of the severe Side Effects are suicidal thoughts and changes in behaviour, like,

  • Mania/hypomania 
  • abnormal heart rhythm function 
  • bleeding allergic reaction 
  • skin rashes 
  • behaviour changes like hallucinations 
  • low sodium level
  • seizure
  • difficult to urinate.
  • signs of anorexia
  • tremor
  • Racing heartbeat

If you experience any of the above, kindly visit your doctor immediately.

Usually, SSRI group drugs have the presence of Addiction naturally. It is possible to develop a physical addiction process to the drug; some antidepressants have withdrawal effects due to the sudden stoppage of the drug.
Yes, according to the study, there is evidence of weight gain for people using Prozac for a more extended period. We can't say antidepressants lead to weight gain; some factors denote weight gain; due to depressive disorder, you are probably less active, and this tends to gain weight in adults.
Studies show people taking less than 25 years of age taking antidepressants for any condition will probably feel sad, have behaviour changes and even have suicidal thoughts due to the drug's effect.

Precautions Of Prozac 

Before using the medication, inform your doctor about your medical condition and the medication history or if you have any allergies to the drug; if you are pregnant or breastfeeding, tell your doctor about some of the complications listed below 

Allergic reactions

People with allergic reactions taking the drug will have rashes. If you face any swelling or rashes, inform your doctor and stop the medication as soon as possible


The drug can reduce the number of platelets present in the blood, which can make it difficult to stop your bleeding from any sudden cuts or injuries. Such as, if you experience some unexplained  bleeding, inform your doctor 

People With Diabetes

The drug may change the sugar level if you have a diabetic patient; inform your doctor before taking the medication,

People with Glaucoma

The drug leads to increased pressure in your eye and worsens your condition. If you have an eye infection, inform your doctor about your situation before taking the medication. Your doctor may adjust the Sa age 

People With Heart Function

The drug will lead to increased QT prolongation of the heart rate, called a severe life-threatening condition; they may suffer from seizures and fainting. If you have any heart-related disease, inform your doctor before taking the drug.

Psychotic Condition     

Using the drug may cause mania episodes, especially for bipolar disorder. If you notice any high level of energy, hallucination and aggression, inform your doctor immediately. 


Pregnant women reported using in the last trimester may experience side effects such as breathing problems, seizures, trouble and crying. This may lead to an increase in the congenital disabilities of the foetus. So do not use this drug during your pregnancy.


The drug will pass into your breast milk. If breastfeeding your baby, it may affect your baby's health, so inform your doctor before consuming. 

Drug Interactions Of Prozac 

Prozac may interact with other drugs, such as MAOIs, antipsychotic drugs, and antidepressants. Some of the interaction will lead to side effects of internal bleeding and seizures. So before taking the medication, consult your doctor about your medical history.
Some of the Serious drug interactions are:

Drugs like NSAIDs, Aspirin and warfarin

While taking medications like NSAIDs, aspirin and warfarin will interfere with Prozac and increase the risk of gastrointestinal bleeding in your system.

Serotonergic Drugs

Avoid taking monoamine oxidase inhibitors, tricyclic antidepressants, fentanyl, tramadol, buspirone, and the level of serotonin syndrome when consumed with Prozac. 

Electroconvulsive Therapy

Avoid therapies because they cause sudden prolongation and develop seizure attacks.

Anticonvulsant Drugs

Medications like carbamazepine, phenytoin,  and oxcarbazepine can cause anticonvulsant toxicity while taken with Prozac. 

It causes adverse effects on the users of Person consuming Marijuana, muscle relaxers, codeine or alcohol.

Bottom Line From Practical Anxiety Solutions 

We understand the drug Prozac; it is an antidepressant drug that belongs to a group of Selective serotonin reuptake inhibitors. It is safe and effective to treat depression, anxiety and other disorders. The drug can have some adverse effects due to the ideal thoughts in people.

Some drug interactions should be discussed before taking the Drug because taking this Drug with the Monoamine oxidase inhibitors group of drugs will be very harmful to you while consumed together.
If you wish to discontinue the drug, contact your doctor and stop using the medicine because your doctor will help you to overcome this withdrawal effect by reducing the dosage. 

  • Wong, David T., Frank P. Bymaster, and Eric A. Engleman. "Prozac (fluoxetine, Lilly 110140), the first selective serotonin uptake inhibitor and an antidepressant drug: twenty years since its first publication." Life sciences 57.5 (1995): 411-441. From Obtained on 21/11/2022
  • Andersen, Jacob, et al. "Molecular basis for selective serotonin reuptake inhibition by the antidepressant agent fluoxetine (Prozac)." Molecular pharmacology 85.5 (2014): 703-714. From  Obtained on 21/11/2022
  • Altamura, Alfredo C., Anna R. Moro, and Mauro Percudani. "Clinical pharmacokinetics of fluoxetine." Clinical pharmacokinetics 26.3 (1994): 201-214. Obtained on 21/11/2022 
  • Sawyer, E. K., and L. L. Howell. "Pharmacokinetics of fluoxetine in rhesus macaques following multiple routes of administration." Pharmacology 88.1-2 (2011): 44-49. From  Obtained on 21/11/2022
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