Network protocols that use aggressive retransmissions to compensate for packet loss due to congestion can increase congestion, even after the initial load has been reduced to a level that would not normally have induced network congestion. Such networks exhibit two stable states under the same level of load.
Beta blocker. Beta blocker, also written Î²-blocker, is a class of medications that are particularly used to manage cardiac arrhythmias, and to protect the heart from a second heart attack (myocardial infarction) after a first heart attack (secondary prevention).
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.