I have always used ibuprofen for cramps with success. You can get this just about anywhere and it works within 20 to 30 minutes. It comes in a number of brand names such as Advil or Motrin but generic ibuprofen works great for cramps. And it is inexpensive. good luck
For menstrual cramps, you can use over the counter pain relief medications. Make sure that you follow the directions on the packet. If you do choose to purchase Ibuprofen, be careful with this and make sure that you take the medication after you have had some food. It is known to cause stomach bleeds as well as kidney and liver problems.
As a home remedy, use a heat pack or a hot water bottle wrapped in a towel so that you do not get a heat burn. Put this on your tummy or on your back, whichever is the worst. Or get 2 heat packs and have one for your back and one for your tummy. You may also feel some relief having a comfortably hot bath.
To help lessen menstrual cramps long term, eat a healthy and well balanced diet with lots of fresh fruit and vegetables. Avoid all sugary foods, processed and junk foods. Avoid white products like white bread etc. Use wholemeal varieties. Avoid fizzy drinks and keep your alcohol, coffee and tea to a minimum. Drink milk and more water.
You may also find Evening Primrose Oil helpful. The Evening Primrose Oil comes in capsule form and you can purchase this from the large supermarket and also from a herbal shop as well as on line.