Low doses of anti-depressants like fluoxetine (Prozac) can
help in preventing symptoms of premenstrual syndrome (PMS), according to scientists
from the University of Bristol, UCL and the University of Sao Paolo-Ribeiro
Preto in Brazil.
Up to 80 percent of women suffer from PMS, with symptoms
such as anxiety, irritability, fatigue, sleep deprivation and increased pain sensitivity.
Towards the end of the menstrual cycle there is decreased secretion of the
ovarian sex steroid hormone progesterone. Decline in progesterone leads to decline
in its breakdown product allopregnanolone, which acts in the brain as a potent
sedative and tranquilizing agent. This appears to trigger PMS.
Mice studies have shown that short term treatment with low
doses of the anti-depressants such as fluoxetine can inhibit a specific enzyme
in the brain, which deactivates allopregnanolone, therefore maintaining the
chemical balance of this in-built tranquilizer in the brain, and could be used
to alleviate symptoms of progesterone withdrawal such as PMS and possibly also
postnatal depression. It also blocked the increase in excitability of brain
circuits involved in mediating the stress and fear responses that normally
occur during this phase of the cycle.
The effective dose of fluoxetine was well below that needed
to produce antidepressant effects and this effect was seen within hours of
administration, unlike the two to three weeks of treatment normally needed when
fluoxetine is used to treat depression.
Dr Lovick, from the School of Physiology and Pharmacology at
the University of Bristol said, "The work is important because it
introduces the possibility for targeted, intermittent therapy for PMS in women,
with minimal side effects."