From the Guidelines
Common side effects of Prozac (fluoxetine) include nausea, headache, insomnia, drowsiness, anxiety, nervousness, and decreased appetite, as well as sexual dysfunction, diarrhea, dry mouth, sweating, and dizziness, with most side effects being mild to moderate and improving within the first few weeks of treatment 1.
Common Side Effects
The most commonly reported adverse events associated with fluoxetine include:
- Constipation
- Diarrhea
- Dizziness
- Headache
- Insomnia
- Nausea
- Sexual adverse events
- Somnolence These side effects are generally similar to those of other second-generation antidepressants, with some differences in the incidence of specific adverse events 1.
Severe Adverse Events
Severe adverse events associated with fluoxetine include:
- Sexual dysfunction, with paroxetine having higher rates of sexual dysfunction than fluoxetine, fluvoxamine, nefazodone, or sertraline 1
- Suicidality, with some studies suggesting an increased risk of nonfatal suicide attempts associated with SSRIs, including fluoxetine 1
Management of Side Effects
To minimize side effects, patients can start with a lower dose of fluoxetine (typically 10mg daily) before increasing to the standard dose (20mg daily) 1. Taking fluoxetine in the morning may help reduce sleep disturbances. If side effects become severe or persistent, patients should consult their healthcare provider rather than stopping the medication abruptly, as sudden discontinuation can cause withdrawal symptoms.
Quality of Life
The available evidence does not support clinically significant differences in efficacy, effectiveness, or quality of life among SSRIs, including fluoxetine, for the treatment of acute-phase major depressive disorder 1. However, fluoxetine may have a slower onset of action compared to some other antidepressants, such as mirtazapine 1.
From the FDA Drug Label
In US placebo–controlled clinical trials for major depressive disorder, 12% to 16% of patients treated with Prozac and 7% to 9% of patients treated with placebo reported anxiety, nervousness, or insomnia. In US placebo–controlled clinical trials for OCD, insomnia was reported in 28% of patients treated with Prozac and in 22% of patients treated with placebo Anxiety was reported in 14% of patients treated with Prozac and in 7% of patients treated with placebo. In US placebo–controlled clinical trials for bulimia nervosa, insomnia was reported in 33% of patients treated with Prozac 60 mg, and 13% of patients treated with placebo Anxiety and nervousness were reported, respectively, in 15% and 11% of patients treated with Prozac 60 mg and in 9% and 5% of patients treated with placebo Among the most common adverse events associated with discontinuation (incidence at least twice that for placebo and at least 1% for Prozac in clinical trials collecting only a primary event associated with discontinuation) in US placebo–controlled fluoxetine clinical trials were anxiety (2% in OCD), insomnia (1% in combined indications and 2% in bulimia), and nervousness (1% in major depressive disorder) In addition, the following adverse events were reported at an incidence of at least 2% for fluoxetine and greater than placebo: thirst, hyperkinesia, agitation, personality disorder, epistaxis, urinary frequency, and menorrhagia The most common adverse event (incidence at least 1% for fluoxetine and greater than placebo) associated with discontinuation in 3 pediatric placebo–controlled trials was mania/hypomania (1.8% for fluoxetine–treated, 0% for placebo–treated).
The common side effects of fluoxetine (Prozac) include:
- Anxiety (12% to 16% in major depressive disorder, 14% in OCD, and 15% in bulimia nervosa)
- Insomnia (28% in OCD, 33% in bulimia nervosa, and 1% to 2% in combined indications)
- Nervousness (7% to 11% in major depressive disorder, OCD, and bulimia nervosa)
- Thirst, hyperkinesia, agitation, personality disorder, epistaxis, urinary frequency, and menorrhagia (at least 2% incidence) 2 2
- Mania/hypomania (1.8% in pediatric patients)
- Diarrhea (10% in Prozac Weekly clinical trials) 2
From the Research
Common Side Effects of Fluoxetine
The common side effects of fluoxetine (Prozac) include:
- Nausea 3, 4, 5, 6
- Nervousness 3, 4, 5
- Insomnia 3, 4, 5
- Headache 3, 4, 7
- Somnolence 4
- Sexual dysfunction 6, 7
- Dry mouth 7
- Constipation 7
Resolution of Side Effects
Most adverse events associated with initiating fluoxetine treatment, including nausea, insomnia, nervousness, and somnolence, resolve in the majority of patients and become significantly less frequent with continued treatment over a 6-month period 4.
Serious Side Effects
Fluoxetine has been reported to have few serious side effects, with no evidence of producing a flu-like syndrome or neuropathy similar to that seen with zimelidine 5. However, it can cause the "serotonin syndrome", cardiovascular complications, extrapyramidal side effects, and an apparently increased risk of suicidality 6.