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.
Two beta blockers are currently FDA approved for use in the preventative treatment of migraine: propranolol (Inderal and Inderal LA) and timolol (Blocadren). Three other beta blockers are also used, although these drugs are not approved by the FDA for indication in migraine. These three agents are: atenolol (Tenormin), metoprolol (Lopressor), and nadalol (Corgard). Blockade of these beta adrenergic receptors results in inhibition of arterial dilatation.