Final answer:
NSAIDs are prescribed to treat primary dysmenorrhea on an 'as needed' basis, often beginning at the onset of menstruation to reduce pain and inflammation caused by prostaglandins.
Step-by-step explanation:
Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly prescribed to treat primary dysmenorrhea, which is a term for pain associated with menstruation. These medications work by inhibiting the production of prostaglandins, reducing inflammation and uterine contractions. For the management of dysmenorrhea, NSAIDs are often prescribed on an as-needed basis, starting at the onset of menstruation or when the cramps begin, and continuing as per the individual's symptoms and pain level. In some cases, a scheduled regimen might be recommended to provide consistent relief during the menstrual period.