Duloxetine and fluoxetine are prescription medications that are used to treat depression. Although both drugs are antidepressants, they work differently in the body. Antidepressants fall into several categories, but the two most common are serotonin-norepinephrine reuptake inhibitors (SNRIs) and selective serotonin reuptake inhibitors (SSRIs). Duloxetine is an SNRI medication, and fluoxetine is an SSRI medication.

Read on to learn how these antidepressants work in the body and how to determine which one is right for you or your loved one.


Duloxetine, more widely known by the brand name Cymbalta, can be prescribed to treat various conditions in addition to major depressive disorder (MDD), including generalized anxiety disorder (GAD), fibromyalgia, and chronic musculoskeletal pain. The medication was approved in 2004, and it works by regulating serotonin and norepinephrine neurotransmitters in the brain.

It is usually taken one or two times a day with or without food, and the dose can range from 20 mg (milligrams) to 120 mg. A doctor or other health care provider can help determine the correct dose for patients. Usually, people who take duloxetine start off with a low dose that is gradually increased over several weeks.


Fluoxetine is an antidepressant that is recognized by its trade name Prozac. Its classification as a selective serotonin reuptake inhibitor (SSRI) means it works by enhancing the effects of serotonin in the brain. It can be prescribed to treat mental disorders such as obsessive-compulsive disorder (OCD) and depression, but it might also be used to treat panic disorders and bulimia, an eating disorder.

Patients may take fluoxetine by mouth as a capsule, a tablet, or as a delayed-release capsule. They also can take the medication as a solution orally. Fluoxetine can be taken with or without food. If you have been prescribed this medication, your doctor may start you on a low dose that will be increased gradually.

Fluoxetine comes in capsule form and in various doses, from 10 milligrams (mg), 20 mg, and 40 mg. Doctors recommend that the maximum effective dose is 80 mg per day. A delayed-release 90 mg oral tablet can be taken every week.

According to MedlinePlus, patients may not feel the full benefit of fluoxetine until after four to five weeks after use. It advises people who are on this medication on prescription to continue taking it, even if they feel well.

“Do not stop taking fluoxetine without talking to your doctor,” MedlinePlus writes. Sudden cessation of antidepressant use can bring on unwanted withdrawal symptoms.

Duloxetine And Fluoxetine Compared

There are similarities between duloxetine and fluoxetine, but there are key differences, too, as they are in different categories of antidepressants.

Duloxetine is prescribed for:

  • Depression
  • Obsessive-compulsive disorder (OCD)
  • Panic disorder
  • Bulimia (eating disorder)

While fluoxetine is prescribed to treat:

  • Anxiety disorders
  • Depression
  • Neuropathic pain stemming from diabetes
  • Musculoskeletal pain (chronic)
  • Fibromyalgia
  • Panic attacks
  • Depressive episodes linked with Bipolar I Disorder (The medication can be paired with olanzapine (Zyprexa).)

The two medications also have side effects.

Side effects of duloxetine include:

  • Diarrhea
  • Sleepiness, drowsiness
  • Decreased appetite
  • Headache
  • Constipation
  • Nausea
  • Dry mouth
  • Insomnia
  • High blood pressure

Side effects of fluoxetine include:

  • Dizziness
  • Shaking
  • Agitation
  • Headache
  • Fatigue
  • Insomnia
  • Sleepiness, drowsiness
  • Nervousness
  • Nausea
  • Dizziness
  • Sore throat
  • Flu-like symptoms
  • Decreased libido
  • Ejaculation disorder
  • Indigestion


Which Is More Dangerous?

While medications have therapeutic benefits, they also can have dangers that should be known before taking them. If you have been prescribed either of these medications, be aware that they both have their warnings and take precautions if planning to use them.


Eli Lilly, the maker of duloxetine (Cymbalta), has published a medical guide to inform users about the drug. Included in there are dangerous side effects that the medication can cause. Among them are:

  • Abnormal bleeding
  • Blood pressure changes
  • Severe skin reactions
  • Suicidal thoughts

The guide also warns about serotonin syndrome, which is when too much serotonin floods the brain and builds up in the body. Serotonin syndrome is life-threatening, and medical attention should be sought immediately. Symptoms of this condition include:

  • Agitation
  • Hallucinations
  • Coordination problems
  • Twitching
  • Racing heartbeat
  • High or low blood pressure
  • Nausea
  • Vomiting
  • Sweating, fever
  • Diarrhea
  • Seizures
  • Tremors
  • Dizziness
  • Muscle Rigidity
  • Coma (or other mental status changes)


While fluoxetine (Prozac) is generally considered safe for patients to take, there are side effects that warrant concern. Eli Lilly has also created a medical guide for fluoxetine. According to Medical News Today, it should not be used with some drugs, such as monoamine oxidase inhibitors (MAOIs).

Adverse effects include:

  • Suicidal thoughts in some children, teenagers, or young adults. (The drugmaker says these thoughts can occur within the first few months of treatment or when the dose is changed.)
  • Abnormal bleeding
  • Visual problems
  • Seizures or convulsions
  • Appetite changes

Fluoxetine use can also cause serotonin syndrome (see above). The presence of too much serotonin in the body is considered an overdose and should be treated immediately.

Which Medication Should I Choose?

If you receive treatment for any of the disorders mentioned above, please speak with a medical professional who can diagnose your condition correctly and ensure you receive the right medications. Not all antidepressants are the same, so meeting with a health care professional helps ensure you take the medication safely.

It is common for doctors to start patients on a low dosage of medication to see how well it works before increasing it. If results are unfavorable and adjustments are needed, the physician may start you on another medication to see if it works better. Each case is different, so for the best outcome, consult with your doctor before making changes to your medication.

Summarizing The Two Drugs

These two medications are both prescribed to treat depression, while one is an SNRI, and the other is an SSRI. Due to their specific uses, one may be preferred over the other. Still, it will be solely dependent on the condition the person is struggling with. Both medications are available in oral form. Again, duloxetine comes in a delay-release capsule taken daily, while fluoxetine is available as a daily oral capsule or delayed-release tablet that is taken weekly.

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