There are various sampling methods. The one chosen will depend on a number of factors (such as time, money etc.). 1. Random Sampling Everyone in the entire target population has an equal chance of being selected. This is similar to the national lottery.
Various types of medications have been evaluated for migraine prophylaxis, including beta blockers, antidepressants, anticonvulsants, nonsteroidal anti-inflammatory drugs (NSAIDs), angiotensin blockade agents, and calcium channel blockers.
Tricyclic antidepressants are sometimes prescribed to treat various types of pain, including headache. Amitriptyline (Elavil, Endep) is the best studied for pain relief and the most often prescribed for migraine prevention: it's about 60% effective in thwarting such headaches. Other tricyclics used in migraine prevention include doxepin (Adapin, Sinequan), imipramine (Tofranil), and nortriptyline (Aventyl, Pamelor).