Dulofor and Duloxetine Mylan are substitutes and contain the same active ingredient - duloxetine. In practice, this means that both drugs work in a very similar way and can cause the same side effects, as the main active ingredient is responsible for their therapeutic effect.

More about what are drug substitutes: https://www.gdziepolek.pl/artykuly/czym-sa-zamienniki-lekow

Duloxetine can cause menstrual disorders, although this is a fairly rare side effect. This medicine affects the levels of neurotransmitters in the brain, which may affect the endocrine system, including the regulation of the menstrual cycle, which may be associated with irregular cycles, amenorrhea, delayed or shortened cycles, or changes in the amount of bleeding. This does not pose a health risk and usually does not require stopping treatment. However, it is worth reporting the occurrence of such an adverse reaction to the attending physician.

To sum up, amenorrhea does not have to be related to the start of the replacement and may result from the cumulative effect of duloxetine, which has been used for some time, on the endocrine system.

I am attaching a helpful article: https://www.gdziepolek.pl/artykuly/czy-bac-sie-dzialan-niepozadanych-lekow

Reporting side effects allows you to gather more information about the safety of medicines and update data on them, which can help other patients in the future. We wrote about how to report them here: https://www.gdziepolek.pl/artykuly/jak-i-dlaczego-zglaszac-dzialania-niepozadane

Adverse drug reactions can also be reported individually: https://www.urpl.gov.pl/pl/produkty-lecznicze/monitorowanie-bezpieczeństwa-leków/zg moose-side-effect-0