How Exactly Does Prozac Work?

Prozac is one of the most widely prescribed and administered anti-depressants on the planet. But what is it?
Christopher McFadden

Once touted as the magic bullet to treat depression and anxiety, Prozac is one of the most widely prescribed anti-depressants on the planet. But how does it work exactly? 


What is Prozac?

Prozac is one of many brand names for the antidepressant fluoxetine. It is most often administered to patients to help treat depressionpanic attacksobsessive-compulsive disorder, a certain eating disorder (bulimia), and a severe form of premenstrual syndrome (premenstrual dysphoric disorder).

It is a special type of antidepressant known technically as an SSRI or selective serotonin reuptake inhibitor. This class of drugs works by increasing the extracellular (outside the cell) levels of the neurotransmitter serotonin.

It does this by inhibiting the reabsorption of serotonin into presynaptic cells. This, in turn, means there is more of it in the synaptic cleft (bridges between synaptic cells) around to bind to the postsynaptic receptors on their cell membranes.

Serotonin itself is a special chemical in the human body that regulates mood, social behavior, appetite, digestion, sleep, memory, sexual desire, and function.

Low levels of serotonin have been linked to depression for many years. However, if low serotonin levels can be corrected, a patient's general mood and well-being can be rectified, in part.

For this reason, SSRIs like Prozac have been shown to be very effective for treating low serotonin-related issues like depression, anxiety, etc.

Prozac was first developed in the late 1980s and is, today, one of the most widely prescribed antidepressant drugs in the world.

"Around 1 in 10 people in the United States (U.S.) are thought to use SSRI drugs, and 1 in 4 women in their 40s and 50s." - Medical News Today

Prozac can be administered in various forms including liquid, tablet, and delayed-release long-acting capsules. It is considered safe for adults and, in some cases, it can even be used by children over the age of 10 years.

What is the effect of Prozac?

Patients that are using Prozac often show a marked improvement in mood, sleep, and appetite. Their energy levels also increase and it may even help restore their interest in daily chores. 

what is prozac
Source: Nina Childish/Flickr

Furthermore, Prozac can also decrease a patient's experience of fear, anxiety, unwanted thoughts and a number of panic attacks.

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"It may also reduce the urge to perform repeated tasks (compulsions such as hand-washing, counting, and checking) that interfere with daily living. Fluoxetine may lessen premenstrual symptoms such as irritability, increased appetite, and depression. It may decrease binging and purging behaviors in bulimia." -

But like any medication, it can have some undesirable side effects and interactions with other medications.

Common side effects of taking Prozac include, but are not limited to: -

  • feeling sick (nausea).
  • headaches.
  • being unable to sleep.
  • diarrhea.
  • feeling tired or weak.

In less than 1% of patients, there are also some serious side effects that can result from taking Prozac. These can include, though are very rare (courtesy of the UK's National Health Service): -

  • Chest pain or pressure, or shortness of breath.
  • Severe dizziness or passing out.
  • Painful erections that last longer than 4 hours - this may happen even when you are not having sex.
  • Any bleeding that is very bad or that you cannot stop, such as cuts or nosebleeds that won't stop within 10 minutes.
  • Serious allergic reactions that lead to anaphylaxis.
  • Headaches, trouble focusing, memory problems, not thinking clearly, weakness, seizures, or losing your balance - these can be signs of low sodium levels.
  • Thoughts about harming yourself or suicide.
  • Fits, feelings of euphoria, excessive enthusiasm or excitement, or a feeling of restlessness that means you can't sit or standstill.
  • Vomiting blood or dark vomit, coughing up blood, blood in your pee, black or red poo - these can be signs of bleeding from the gut.
  • Bleeding from the gums or bruises that appear without a reason or that get bigger.

How quickly does Prozac work for anxiety?

For people who suffer from the crippling effects of anxiety, Prozac can help change their quality of life for the better. According to the NHS patients can see improvement within weeks of starting a course of the medication.

"You may see an improvement in your symptoms after 1 to 2 weeks, although it usually takes between 4 and 6 weeks before you feel the full benefits. That's because it takes around a week for fluoxetine levels to build up in your body, and then a few weeks longer for your body to adapt and get used to it." - NHS.

Other symptoms related to low serotonin levels, like the disruption of normal sleep patterns or loss of appetite, can also show marked improvement within a few weeks. Such physical improvements are usually a good sign that the medication is working as hoped.

The reason it takes some time for anti-depressants like Prozac to work is that they need to build up in your system. Remember that any medication is slowly but surely metabolized, or destroyed, by your body (usually in the liver) at a certain rate.

If you stop taking it for even a few days, your body will constantly work to remove it from the body over time. It's a literal battle of attrition. 

For this reason, you shouldn't expect it to work within the first few days of starting a course of the drug. This is also a reason why you should take the drug regularly as prescribed and not miss a dose.

what is prozac pills

Does Prozac help anxiety?

As we have already seen, Prozac can often help battle anxiety. It is considered safe for use by most adult sufferers and has been shown to be effective at treating depression, anxiety, and obsessive-compulsive disorder (OCD), and bulimia.

That being said, it is not foolproof and you might be unlucky enough to experience some of the adverse effects of the drug detailed above.

For depression, the efficacy of Prozac appears to be pretty limited. According to an article in the New Scientist;

"Prozac does not work in the majority of depressed patients. The antidepressant Prozac and related drugs are no better than placebo in treating all but the most severely depressed patients, according to a damaging assessment of the latest generation of antidepressants".

Takeaway facts about Prozac

  • Prozac, also known as fluoxetine, is a type of drug called a selective serotonin reuptake inhibitor (SSRI) and a widely used antidepressant.
  • the drug is widely considered safe and has been shown to be effective in treating depression, anxiety, and obsessive-compulsive disorder (OCD), and bulimia.
  • Despite its advantages, it can have some serious adverse effects include an increased risk of suicidal thoughts in some younger people.
  • Prozac should never be used with monoamine oxidase inhibitors (MAOIs) and some other drugs.
  • If you have become reliant on Prozac, it does have some withdrawal effects. Anyone who wishes to stop using Prozac should do so gradually, with a doctor's help, to prevent adverse reactions.
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