Which medicine can you use to reduce the menstrual pain?

Masso has given you some excellent advice. In addition I've used the Thermacare heat pads that wrap around your waist for lower back pain. I simply wear it backwards so the heat pouch part is against my lower stomach. Once exposed to air they get really warm and last for 6-8 hrs. It's literally like having a heating pad without the restraints of having to be stationary and plugged in! Hope this helps!

Treatment
To ease your menstrual cramps, your health care provider might recommend:

Pain relievers. Over-the-counter pain relievers, such as ibuprofen (Advil, Motrin IB, others) or naproxen sodium (Aleve), at regular doses starting the day before you expect your period to begin can help control the pain of cramps. Prescription nonsteroidal anti-inflammatory drugs also are available.

Start taking the pain reliever at the beginning of your period, or as soon as you feel symptoms, and continue taking the medicine as directed for two to three days, or until your symptoms are gone.

https://www.drugs.com/cg/dysmenorrhea.html

It would also be good to ask your Pharmacist´s recommendations.