Mefenamic acid is used to treat primary dysmenorrhea (period pain) that is not adequately controlled by suitable lifestyle changes and use of other painkillers such as Ibuprofen and Paracetamol.
It is an NSAID (Non-steroidal Anti inflamatory drug) which acts to reduce the production of prostaglandins which is a chemical released during a period.
Prostaglandins cause increased contraction of the muscular wall of the uterus. This leads to an increase in pain. By reducing the production of prostaglandins, NSAIDs such as Mefenamic Acid reduce the contraction of the muscular wall of the uterus and subsequently reduce the pain experienced during a period.