<prompt> A reasonable explanation for the therapeutic effects of ibuprofen or naproxen in primary dysmenorrhea is that these drugsPGE, and PGF2aselectively inhibit COX 2LTB,inhibit PLA2  <response>: PGE, and PGF2a both increase in primary dysmenorrhea, and the therapeutic effects of NSAIDs appear to be due to inhibition of the synthesis of these prostaglandins. Both ibuprofen and naproxen are nonselective COX inhibitors that can inhibit the synthesis of prostacyclin PGI2 . NSAIDs do not inhibit phospholipase A2 , and they do not decrease leukotrienes. 