Migraines are caused by changes in certain blood vessels of the brain that result in a local disturbance in the action of a specific nerve-activating chemical
Two migraine remedies, drug K and drug L, have exactly the same restorative effects on the local action of this chemical, but L also disrupts the action of several other chemicals in the brain that governmental activity and the body' s metabolism
Neither treatment with L nor treatment with K is likely to have a significant effect on the symptoms of a migraine.