Prozac (Fluoxetine) Common Side Effects And Adverse Reactions

Last Updated: June 24, 2020

Authored by Roger Weiss, MD

Reviewed by Michael Espelin APRN

Prozac or Fluoxetine is an antidepressant for treating mood problems like obsessive-compulsive disorder, depression, and panic attacks. It also treats various kinds of eating disorders and is one of the most popular drugs among its kind, available both in brand and generic versions.

What Does Prozac Do to The Body?

Like other antidepressants, Fluoxetine boosts the supply of serotonin in the brain. Serotonin is a neurotransmitter that is often called the happy chemical as it contributes to an individual’s overall happiness and wellbeing. However, the human brain has a complex nature, and every neurotransmitter performs various jobs. Merely increasing the number of happy chemicals in the brain might alleviate depression and lower neuropathic pain, but this could also lead to certain Prozac side effects. The adverse effects of Fluoxetine could range from slightly troublesome to highly debilitating or fatal.

Common Prozac Side Effects

woman falling alseep at her workplaceHere are some of the common side effects of Fluoxetine:

  • Nausea
  • Anxiety
  • Dry mouth
  • Upset stomach
  • Headaches
  • Drowsiness
  • Dizziness
  • Constipation
  • Nervousness
  • Weight changes
  • Heart palpitations
  • Sleep problems (insomnia)
  • Cold symptoms (stuffy nose, sneezing, sore throat)

Weight Gain and Loss on Prozac

Weight changes are one of the infrequent side effects of Prozac, but the two do have a correlation. Weight gain on Prozac could be due to the increased appetite among those who take antidepressants. Many people report feeling hungry all the time or having cravings for sugary foods. If this is the case, pair treatment with balanced diet and regular exercise. Considering proper proportions of proteins, carbs, and good fats will reduce the cravings, and this could even help in losing weight. On the contrary, some people who take Fluoxetine also report incidences of weight loss. According to a study conducted by the “American Family Physician”, Fluoxetine may lead to short-term weight loss of up to 7 pounds among obese patients. However, there’s no solid evidence that the effect will be consistent. Physical activity and healthy diet is still the best way to prevent obesity.
If experiencing excessive weight gain or weight loss, consult a doctor about switching medications. As humans are wired differently, an antidepressant that works well for one may not be as successful for another. The same goes in terms of their adverse effects. Switching to another antidepressant other than Fluoxetine may help in achieving the  main objective without the unwanted Prozac effects, be it weight gain or weight loss.

Prozac Sexual Side Effectssad couple with sexual problems sitting in bed

The is one of the less common adverse effects. However, some patients who take Fluoxetine do complain about erectile dysfunction, low libido, and difficulties with orgasm. These Prozac sexual side effects possibly emerge because when serotonin levels increase, dopamine levels could reduce, and dopamine is the neurotransmitter responsible for arousal. To avoid this side effect, try taking a lower Prozac dosage. One may also just take the pill after sex or take a drug which treats sexual dysfunction, like Viagra or Cialis. Other alternatives include vibratory stimulation or exercising before combining Prozac and sex.

Does Prozac Make One Tired?

Fatigue is one of the common adverse effects of antidepressants like Fluoxetine. They cause fatigue as they make neurotransmitters as serotonin and norepinephrine linger in the spaces between the nerve cells where they do their job of regulating the mood. To minimize this side effect, pop the pill during bedtime, take a nap during the day, or practice regular exercise. Also, avoid combining alcohol and Prozac as well as any medications that can be sedating so the fatigue won’t go worse.

Does Prozac Cause Heartburn?

Some Fluoxetine users experience heartburn although this side effect is not widespread. Antidepressants work as muscle relaxants. Thus, they may relax even the lower esophageal sphincter LES, which eventually increases gastric acid secretion. To avoid Fluoxetine side effects like this, stay upright for around 20 minutes after taking Fluoxetine.

Long-term Adverse Effects of Prozac

In 2016, Patient Preference and Adherence published a paper demonstrating the experiences of the people who take antidepressants like Fluoxetine long-term. Generally, they claimed that they were less depressed, but experienced specific adverse effects. The long-term dangers of Prozac include:

  • Weight gain
  • Feeling numb emotionally
  • Caring less about others
  • Not feeling like themselves
  • Feeling addicted
  • Feeling suicidal

Because of the possible health and social harm they can bring, taking SSRIs like Prozac has been considered a public health issue. It’s essential to understand how SSRIs affect the mind and the body, especially in the long-term.
Dr. Ben Weinstein, a psychiatry professor at Baylor College of Medicine, states that there are lots of controversy in the global medical community about SSRIs’ long-term effects due to them being overused or overprescribed. Though this doesn’t mean doctors shouldn’t prescribe them at all, it’s important to take their long-term effects more seriously.

Long-term heart problems and the risk of diabetes

A user that takes high doses of Prozac in an extended period could experience seizures and  heart rhythm abnormalities. Heart problems may be due to the typical weight gain that users experience. A study published in the Journal of Clinical Psychiatry demonstrates that long-term SSRI users including Fluoxetine are also at risk of developing Type 2 diabetes. The risk of diabetes among those aged 44 years and below is higher as compared to older adults.

Organoleptic reactions

man with eyeglasses rubbing his eyesClinical and anecdotal reports also stated that some other long-term effects of taking Prozac include an altered sense of smell, hearing, or taste, food/drug intolerances, constant pain, visual problems, burning hands and feet, and so on. Some of these effects are felt when a user stops taking the Fluoxetine.
Upon taking SSRIs long-term, the neurotransmitters of the brain may get used to functioning in a specific way. It would then be hard for the brain to return to the normal functioning, and when discontinued, the user may experience withdrawals of discontinuation syndrome. Further withdrawal symptoms of Fluoxetine include disrupted sleep patterns, tremors, digestion issues, etc. that could go on for weeks or months.
Around 74% of the people also had withdrawal symptoms. There are various side effects of stopping Prozac. That’s why patients shouldn’t stop taking Fluoxetine abruptly. Patients should consult a specialist for the proper way of weaning themselves off Fluoxetine.

Prozac and Suicide

Having suicidal tendencies is one of the rare adverse effects of Fluoxetine. Overall, antidepressants are effective in reducing the symptoms of depression. However, certain pieces of evidence suggest that Prozac may worsen suicidal thoughts of vulnerable patients. Although the actual link between antidepressants and suicidality is not yet established, it is said that children and adolescents appear to have increased risk of suicidal attempts and ideations when under Fluoxetine treatment or Prozac overdose.

Getting Professional Help

Like all other drugs, antidepressants like Fluoxetine have their benefits and adverse effects. Just make sure to be well-informed and get professional advice from trusted rehabs and addiction centers to know every step of the process, especially for those who have have Prozac withdrawal symptoms.

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Published on: June 27th, 2018

Updated on: June 24th, 2020

About Author

Roger Weiss, MD

Dr. Roger Weiss is a practicing mental health specialist at the hospital. Dr. Weiss combines his clinical practice and medical writing career since 2009. Apart from these activities, Dr. Weiss also delivers lectures for youth, former addicts, and everyone interested in topics such as substance abuse and treatment.

Medically Reviewed by

Michael Espelin APRN

8 years of nursing experience in wide variety of behavioral and addition settings that include adult inpatient and outpatient mental health services with substance use disorders, and geriatric long-term care and hospice care.  He has a particular interest in psychopharmacology, nutritional psychiatry, and alternative treatment options involving particular vitamins, dietary supplements, and administering auricular acupuncture.


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  • Dianne
    Hi is it safe to increase your prozac dosage i the first week?