Random Drugs Flashcards
Glucagon k notes:
Used for:
1. Profound B-blocker toxicity
2. To relax sphincter of oddi and allow for drainage of bile
Note: sphincter of oddi: valve that controls the flow of bile and pancreatic juice through ampulla of vater into second part of duodenum ( first section of the small intestine followed by jejunum and ileum)
Glucagon
Glucagon is a peptide hormone, produced by alpha cells of the pancreas, that raises the concentration of glucose in the bloodstream. Its effect is opposite that of insulin, which lowers the glucose concentration.[1] The pancreas releases glucagon when the concentration of glucose in the bloodstream falls too low. Glucagon causes the liver to convert stored glycogen into glucose, which is released into the bloodstream. High blood glucose levels stimulate the release of insulin. Insulin allows glucose to be taken up and used by insulin-dependent tissues. Thus, glucagon and insulin are part of a feedback system that keeps blood glucose levels at a stable level. Glucagon belongs to a family of several other related hormones.
Function:
Glucagon generally elevates the concentration of glucose in the blood by promoting gluconeogenesis and glycogenolysis.
Glucose is stored in the liver in the form of the polysaccharide glycogen, which is a glucan (a polymer made up of glucose molecules). Liver cells (hepatocytes) have glucagon receptors. When glucagon binds to the glucagon receptors, the liver cells convert the glycogen into individual glucose molecules and release them into the bloodstream, in a process known as glycogenolysis. As these stores become depleted, glucagon then encourages the liver and kidney to synthesize additional glucose by gluconeogenesis. Glucagon turns off glycolysis in the liver, causing glycolytic intermediates to be shuttled to gluconeogenesis.
Glucagon also regulates the rate of glucose production through lipolysis. Glucagon induces lipolysis in humans under conditions of insulin suppression (such as Diabetes mellitus type 1).[2]
Glucagon production appears to be dependent on the central nervous system through pathways yet to be defined. In invertebrate animals, eyestalk removal has been reported to affect glucagon production. Excising the eyestalk in young crayfish produces glucagon-induced hyperglycemia.[3]
Medical use:
Hypoglycemia
An injectable form of glucagon is vital first aid in cases of severe hypoglycemia when the victim is unconscious or for other reasons cannot take glucose orally. The dose for an adult is typically 1 milligram, and the glucagon is given by intramuscular, intravenous or subcutaneous injection, and quickly raises blood glucose levels. To use the injectable form, it must be reconstituted prior to use, a step that requires a sterile diluent to be injected into a vial containing powdered glucagon, because the hormone is highly unstable when dissolved in solution. When dissolved in a fluid state, glucagon can form amyloid fibrils, or tightly woven chains of proteins made up of the individual glucagon peptides, and once glucagon begins to fibrilize, it becomes useless when injected, as the glucagon cannot be absorbed and used by the body. The reconstitution process makes using glucagon cumbersome, although there are a number of products now in development from a number of companies that aim to make the product easier to use.
Beta blocker overdose
Anecdotal evidence suggests a benefit of higher doses of glucagon in the treatment of overdose with beta blockers; the likely mechanism of action is the increase of cAMP in the myocardium, in effect bypassing the β-adrenergic second messenger system.[4]
Anaphylaxis
Some people who have anaphylaxis and are on beta blockers are resistant to epinephrine. In this situation glucagon intravenously may be useful to treat their low blood pressure.[5]
Impacted food bolus
Glucagon relaxes the lower esophageal sphincter and may be used in those with an impacted food bolus in the esophagus (“steakhouse syndrome”).[6] There is little evidence for glucagon’s effectiveness in this condition,[7][8][9] and glucagon may induce nausea and vomiting,[9] but considering the safety of glucagon this is still considered an acceptable option as long it does not lead to delays in arranging other treatments.[10][11]
