Up to 85% of menstruating women are estimated to experience at least one symptom of premenstrual syndrome during their monthly cycle. But according to two new studies, taking a low dose of the antidepressant fluoxetine, or Prozac, immediately before a premenstrual cycle could prevent such symptoms.

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Researchers say taking a low dose of fluoxetine, or Prozac, right before a premenstrual cycle could prevent symptoms of PMS.

Premenstrual syndrome (PMS) can occur in any woman who is menstruating, but it most commonly occurs among those in their late 20s or early 40s, women who have at least one child and those with a family history of depression, postpartum depression or mood disorders.

Symptoms of PMS occur 1-2 weeks prior to a monthly cycle and include acne, swollen or tender breasts, fatigue, anxiety, mood swings, irritability and increased sensitivity to pain. PMS symptoms usually disappear once the monthly cycle begins.

Although the exact causes of PMS are unclear, researchers believe it may be triggered by reduced secretion of the sex hormone progesterone that occurs toward the end of a menstrual cycle.

The researchers of both studies – led by Dr. Thelma Lovick of the School of Physiology and Pharmacology at the University of Bristol in the UK – explain that a reduction in progesterone causes a fall in the hormone’s breakdown product called allopregnanolone, which acts as a brain sedative.

As such, the researchers say women with PMS experience a type of drug withdrawal response from lack of allopregnanolone. But in their latest research, the team found that fluoxetine could increase levels of allopregnanolone in the brain and prevent symptoms of PMS.

To reach their findings, published in the journal European Neuropsychopharmacology and the British Journal of Pharmacology, the team analyzed the effects of fluoxetine on the brains of adult female rats.

They found that the antidepressant blocked an enzyme in the brain that deactivates allopregnanolone, called 5α-dihydroprogesterone. When given to the rats in a low dose right before their premenstrual cycle, fluoxetine increased allopregnanolone levels in the brain and halted the development of PMS-like symptoms.

The team also found the antidepressant reduced overactivity in brain circuits involved in stress and fear responses – a process that usually occurs prior to the premenstrual cycle.

Notably, the researchers say these PMS-reducing effects occurred within hours of fluoxetine administration. In comparison, it usually takes 2-3 weeks for the drug to work against symptoms of depression.

What is more, the team says they discovered that fluoxetine has the same 5α-dihydroprogesterone-blocking effect in the human brain.

As such, the researchers say fluoxetine could be effective in preventing symptoms of PMS in menstruating women, and it could even be used to treat postnatal depression.

Commenting on their findings, Dr. Lovick says:

The work is important because it introduces the possibility for targeted, intermittent therapy for PMS in women, with minimal side effects.”

Past research has suggested other possible benefits of antidepressants. Earlier this year, Medical News Today reported on a study claiming that a commonly prescribed antidepressant – citalopram – could slow onset of Alzheimer’s disease.