Medical Review by Jennie Stanford, MD, FAAFP, DABOM
Summary
- Prozac® (fluoxetine) is a prescription SSRI antidepressant. It increases serotonin levels in the brain, helping to improve your mood and reduce symptoms of depression.
- You might experience nausea, decreased appetite, insomnia, sexual dysfunction, or increased sweating on Prozac®, especially when you first start taking it.
- Serious side effects are less common on Prozac®, but they can still occur. These include mood changes, serotonin syndrome, hyponatremia, seizures, or unusual bleeding. It’s important to seek medical help if you experience any concerning symptoms.
- If you notice any new or worsening symptoms while taking Prozac®, it’s a good idea to reach out to your healthcare provider. A qualified medical professional can help you manage your side effects and make sure the medication is working as effectively as possible.
Here’s what you need to know as you start taking Prozac®
Prozac® (a branded form of fluoxetine) is a prescription antidepressant belonging to a class of medications called selective serotonin reuptake inhibitors (SSRIs). SSRIs stop a naturally-occurring chemical called serotonin from being absorbed by your brain after it has been produced, increasing the amount of serotonin available.
Boosting serotonin can improve your mood and help relieve symptoms of depression and other conditions. That’s because serotonin is linked to mood, memory, and behavior.
Prozac® is commonly used to treat:
- Major depressive disorder
- Obsessive-compulsive disorder
- Panic disorder
- Bulimia nervosa
While Prozac® can help improve your symptoms, it’s important to know that it may also cause side effects. In this article, we’ll dive deeper into Prozac®’s side effects, and explain why they happen, how they can affect your body, and when to seek help from a healthcare professional.
Common side effects
Side effects can occur with Prozac®, especially when you first start taking the medication. As your body adjusts, you may notice a variety of symptoms ranging from mild to more noticeable.
These side effects are typically most prominent during the first few weeks of treatment as your body adapts to changes in serotonin levels. Some of the most common side effects of Prozac® are as follows:
Nausea
When taking Prozac®, you may experience nausea because it increases serotonin levels in your body. Approximately 95% of your serotonin is stored in your gastrointestinal system, which has many cells that respond to serotonin.
Higher serotonin levels in this area can upset your stomach and cause nausea. In clinical trials, nausea was experienced by 22% of those taking Prozac®, compared to 9% taking a placebo.
Decreased appetite
Serotonin in your brain helps regulate your appetite. When your serotonin levels increase, your appetite and food intake tend to decrease—so taking Prozac® might make you feel less hungry or feel hungry less often.
In clinical trials, 10% of people taking Prozac® had a reduced appetite, compared to just 3% of those on a placebo. Despite this, only 2% of patients actually lost weight while taking Prozac®.
Anxiety
SSRIs, like Prozac®, can have an “activating effect,” which causes your body to release stress hormones like cortisol. While these hormones help you manage stress, they can make anxiety worse. Genetic differences in how your body processes medication can also play a role in how you respond to Prozac®.
In a clinical trial, 12% of people taking Prozac® reported worsened anxiety, compared to 6% of those taking a placebo.
Insomnia
Insomnia is when you have trouble falling asleep, staying asleep, or getting good quality sleep, which leads to problems during the day. In clinical trials, insomnia was experienced by 19% of those taking Prozac®, compared to 10% taking a placebo.
Increasing serotonin levels with medications like Prozac® and other SSRIs can disrupt your sleep because serotonin promotes wakefulness, making it harder for you to fall asleep. Serotonin also helps produce melatonin, the hormone that regulates the sleep-wake cycle. When serotonin levels change, it can affect melatonin production, and make it harder to sleep as well.
Sexual dysfunction
Sexual dysfunction includes issues like ejaculatory delay (taking longer to ejaculate), erectile dysfunction, and a lowered sex drive.
When you take SSRIs, the higher serotonin levels block the brain’s dopamine and norepinephrine pathways, which are important for desire and arousal. Most serotonin is found outside the brain, and when levels are higher, it can reduce sensations in the genitals.
This can lead to erectile dysfunction, low vaginal lubrication, and orgasm problems. Serotonin also blocks the production of nitric oxide, which helps relax blood vessels. Without this, there’s less blood flow to your genitals, which can affect sexual function.
Increased sweating
Excessive sweating is a common and uncomfortable side effect of using antidepressants. About 10% of people on SSRIs experience it.
The exact cause isn’t fully understood, but it’s believed that SSRIs affect serotonin levels in the hypothalamus, the part of your brain that controls your body temperature. This serotonin change may lead to your body sweating more than it should.
Serious side effects
Suicidal thoughts or behaviors
Young people aged 24 and under have a higher risk of suicidal thoughts and behaviors, especially in the first few months of starting an SSRI like Prozac® or after a dose change. The exact reason for this is not fully understood.
The patient information for Prozac® includes data showing that for those under 18, there are 1.4% more cases of suicidal thoughts and behaviors compared to those on a placebo. For those aged 18-24, the increase is 0.5%.
Mania
Mania is a time period of at least one week when a person has a major change in behavior that greatly affects their daily life.
Signs of mania include:
- Increased talkativeness and rapid speech
- Less need for sleep
- Racing thoughts and distractibility
- Upbeat and over-excited
- Mood swings, impulsivity & irritability
If you have bipolar disorder, taking antidepressants like Prozac® can increase your risk of experiencing mania from anywhere between 20-40%. Since many people with bipolar disorder first show depressive symptoms, it’s important to check if you or a family member has a history of bipolar disorder before starting Prozac®.
Typically, manic symptoms from antidepressants appear within a few days to 2 weeks after starting the medication and usually resolve within 2 weeks after stopping it.
Seizures
Generally, the risk of seizures with antidepressants is low and mostly linked to very high doses or overdoses. If you have a history of seizures or epilepsy, you may still be able to use Prozac® safely with careful monitoring by your healthcare provider.
Angle-closure glaucoma
Angle-closure glaucoma is a serious eye problem where pressure builds up quickly inside your eye because the fluid that keeps your eyes nourished can’t drain properly. SSRIs can cause your pupils to dilate (get larger), which can lead to the iris (the colored part of your eye) blocking the eye’s drainage system.
This blockage causes the fluid to build up, increasing eye pressure, and potentially leading to permanent damage if not treated quickly.
Angle-closure glaucoma often comes on suddenly and can cause severe symptoms, including:
- Intense eye pain
- Blurred or reduced vision
- Rainbow-colored halos around lights
- Nausea and vomiting
Increased risk of bleeding
Taking SSRIs like Prozac® can raise your risk of unusual bleeding, especially if you’re also using aspirin, NSAIDs, antiplatelet drugs, or anticoagulants like warfarin. SSRIs increase serotonin levels in your brain by blocking its reabsorption, but they also block serotonin reabsorption in platelets—blood cells that help with clotting.
Serotonin helps platelets to stick together to form clots. When serotonin levels in platelets become low, they are unable to clot together, leading to a higher risk of abnormal bleeding.
Hyponatremia
Hyponatremia is a condition where the sodium levels in your blood get too low. This can sometimes happen when taking SSRIs like Prozac®, especially if you have syndrome of inappropriate antidiuretic hormone secretion (SIADH), which causes the body to hold onto water and dilute sodium. Elderly people, females, and those on diuretics have a higher risk.
Symptoms of hyponatremia include:
- Headache
- Trouble concentrating
- Memory problems
- Confusion
- Weakness and unsteadiness which may lead to falls
In more severe cases, it can cause hallucinations, fainting, seizures, coma, or even life-threatening issues.
Hyponatremia related to SSRIs usually starts within the first two weeks of treatment and is not related to the dose. Sodium levels normally return to normal within 2–20 days after stopping the medication.
Serotonin syndrome
Serotonin syndrome is a serious condition that can be life-threatening. It happens when there’s too much serotonin in your brain, often due to taking medications that boost serotonin levels, especially if you’re using more than one such medication. It can also occur if you’re on a medication that affects how serotonin is broken down, like MAOIs, which prevent serotonin from being used up or removed properly.
Keep an eye out for these symptoms of serotonin syndrome:
- Agitation, hallucinations, confusion, or delirium
- Fast heart rate or increased blood pressure
- Sweating and/or high fever
- Stiff muscles or tremors
- Seizures
- Nausea, vomiting, and/or diarrhea
When to seek medical help
If you have any new or worsening symptoms while taking Prozac®, let your healthcare provider know right away. This includes common side effects like nausea, decreased appetite, anxiety, insomnia, sexual dysfunction, and increased sweating. Your healthcare provider can help manage these side effects and adjust your treatment if needed.
For serious side effects, such as thoughts of self-harm, symptoms of mania, seizures, sudden vision problems, unusual bleeding, or signs of serotonin syndrome—seek emergency care immediately.
Find your Prozac® support system with Lemonaid Health
While side effects from Prozac® can occur, staying in communication with your healthcare provider is the best way to help you manage them effectively. Side effects often improve over time, but if you experience anything serious, seek help immediately. It’s important to inform your healthcare provider about any side effects you notice.
Our team at Lemonaid Health can help. Set up a virtual visit with a qualified US-based health professional who can help you understand any side effects and find appropriate solutions, including FDA-approved medication in clinically indicated cases.
Prozac® is a registered trademark of Eli Lilly and Company.
