A study that analysed 3.4 million UK shoppers between 2006 and 2015 found that paracetamol was most common painkiller bought alongside menstrual products. But experts, cited by BBC, say ibuprofen could be more effective at managing menstrual cramps because it blocks production of prostaglandins. Paracetamol is more effective for headaches as it works primarily in brain to block pain signals.