GnRH antagonists
Just like the GnRH agonists, the GnRH antagonists can also be used in order to prevent premature ovulation during fertility treatments such as in vitro fertilisation (IVF). An example is Orgalutran® .
Whereas an agonist works in the same way as naturally produced GnRH, an antagonist has the opposite effect.
how they work
GnRH antagonists have a more rapid effect than agonists because they directly block LH and FSH production at the level of the pituitary. This means they only have to be administered just before premature ovulation is expected. GnRH antagonists can, as a result, be administered for a much shorter time than agonists. The necessary dosage is also lower than for the GnRH agonists. Experience with GnRH antagonists, however, is still limited.
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how they are administered
GnRH antagonists must, just like most agonists, be administered by injection under the skin at a certain point in the cycle. This generally happens on the fifth to seventh day of the FSH cycle.
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possible side effects
- Local reaction where the injection took place.
- Headaches and nausea (> 1%).
- Dizziness, lethargy, malaise (< 1%).
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