Fluoxetine for PMDD (Premenstrual Dysphoric Disorder)Treatment
- Kate Organ
- Jun 20
- 3 min read
What is PMDD?
Premenstrual Dysphoric Disorder (PMDD) is a severe type of premenstrual syndrome (PMS), affecting about 3–8% of women.
It typically causes distressing symptoms in the 7-14 days before your period (the luteal phase), including:
Low mood or depression
Anxiety
Irritability or anger
Mood swings
Fatigue
Difficulty concentrating
Physical symptoms such as bloating, breast tenderness, joint or muscle aches
Symptoms usually improve within a few days of menstruation starting and are typically absent in the first half of the menstrual cycle.
What is Fluoxetine?
Fluoxetine is a type of antidepressant known as a Selective Serotonin Reuptake Inhibitor (SSRI).
Fluoxetine is licensed in the UK for depression, anxiety, obsessive-compulsive disorder and unlicensed for PMDD.
It works by increasing serotonin — a chemical messenger that helps to regulate mood — in the brain. People with PMDD appear to have abnormal serotonin responses to natural hormonal changes during the menstrual cycle. By improving serotonin signalling, fluoxetine helps reduce both emotional and some physical symptoms of PMDD.
What is the Evidence for Using Fluoxetine in PMDD Treatment?
Numerous high-quality randomised controlled trials (RCTs) show that fluoxetine is effective in treating PMDD.
A Cochrane Review (Wyatt et al, 2004) found that SSRIs, including fluoxetine, significantly reduce PMDD symptoms.
UK guidelines, including NICE Clinical Knowledge Summaries (CKS), Royal College of Obstetricians and Gynaecologists, and British Menopause Society, recommend SSRIs (fluoxetine or sertraline) as first-line treatment for moderate to severe PMDD.
Evidence shows that fluoxetine can improve mood symptoms even when taken only in the luteal phase — this is unique to PMDD treatment, compared to its use in depression.
How Does Fluoxetine Work in PMDD?
Increases serotonin activity
Reduces symptoms such as mood swings, irritability, anxiety, fatigue and concentration problems
Helps improve physical symptoms such as tiredness and sleep difficulties
Can work within 48 hrs (more quickly than in depression, where onset takes 4–6 weeks)
How to Take Fluoxetine for PMDD
Two main options are used in UK practice:
Luteal phase dosing | Continuous dosing |
Fluoxetine is taken only in the second half of the cycle (from ovulation ~ day 14 to the start of the period). | Fluoxetine is taken every day throughout the entire menstrual cycle. |
This option may reduce side effects, as medication is only taken when needed. | This option is helpful if you prefer a simple routine or if symptoms last throughout the cycle. |
Your clinician may suggest this if your symptoms clearly follow a monthly pattern. | Often chosen for more continuous or severe symptoms. |
Usual starting dose: 10–20 mg daily
Your GP or menopause specialist will advise which approach is best for you.
Benefits of Taking Fluoxetine for PMDD
Recommended first-line treatment in NICE CKS and BNF guidance for PMDD
Reduces emotional symptoms in up to 60–75% of people with PMDD
Fast-acting for PMDD — improvements are often seen within the first cycle
Dosing can be flexible — luteal phase or continuous
Well tolerated by most people
Improves quality of life, relationships and functioning at work or home
Possible Side Effects
As with all medicines, some people may experience side effects.
Common (may affect more than 1 in 10 people):
Nausea
Headache
Difficulty sleeping
Tiredness or drowsiness
Anxiety (usually settles after 1–2 weeks)
Reduced sexual desire or function
Less common:
Sweating
Change in weight
Upset stomach
Restlessness
Rare/serious (contact GP urgently if these occur):
Thoughts of self-harm or worsening low mood
Severe agitation
Serotonin syndrome (rare) — symptoms include confusion, high fever, muscle stiffness
Most side effects are mild and settle after the first few weeks.
Is Fluoxetine Addictive?
No — fluoxetine is not addictive. However, stopping suddenly may cause withdrawal symptoms. Your clinician will advise you on how to stop gradually if needed.
Who Should Not Take Fluoxetine?
People allergic to fluoxetine or SSRIs
Those taking certain other medications (e.g. MAO inhibitors) — your GP will check
Caution in pregnancy or breastfeeding — always discuss with your doctor
Summary
Fluoxetine is a well-established, effective treatment for PMDD. It helps balance serotonin function during the premenstrual phase, reducing distressing emotional and physical symptoms.
Dosing can be tailored to suit your cycle — either luteal phase only, or continuously. It can be a helpful option alongside lifestyle changes or hormonal treatments, depending on your needs.
If you would like to know more, speak to our PMDD specialist
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