McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 4 7 Lipid-lowering agents

■■ Fats are metabolised with the aid of bile acids, which act as a detergent to break fats into small molecules called micelles. Micelles are absorbed into the intestinal wall and combined with proteins to become chylomicrons, which can be transported throughout the circulatory system. ■■ Some fats are used immediately for energy or are stored in adipose tissue; others are processed in the liver to LDLs, which are associated with the development of CAD. LDLs are broken down in the periphery and leave many remnants (e.g. fats) that must be removed from blood vessels. This process involves the inflammatory reaction and may initiate or contribute to atheroma production. ■■ Some fats are processed into HDLs, which are able to absorb fats and remnants from the periphery and offer a protective effect against the development of CAD. ■■ Cholesterol is an important fat that is used to make bile acids. It is the base for steroid hormones and provides the necessary structure for cell membranes. All cells can produce cholesterol. ■■ HMG-CoA reductase is an enzyme that controls the final step in the production of cellular cholesterol. ■■ People taking lipid-lowering drugs need to include diet, exercise and lifestyle changes to reduce the risk of CAD. ■■ Bile acid sequestrants bind with bile acids in the intestine and lead to their excretion in faeces. This results in lower bile acid levels as the liver uses cholesterol to produce more bile acids. The end result is a decrease in serum cholesterol and LDL levels as the liver changes its metabolism of these fats to meet the need for more bile acids. ■■ HMG-CoA reductase inhibitors, or statins, block the enzyme HMG-CoA reductase, resulting in lower serum cholesterol levels, a resultant breakdown of LDLs and a slight increase in HDLs. ■■ The cholesterol absorption inhibitor ezetimibe works in the brush border of the small intestine to prevent the absorption of dietary cholesterol, which leads to increased clearance of cholesterol by the liver and a resultant fall in serum cholesterol. ■■ Other agents used to lower cholesterol include fibrates and nicotinic acid. Often lipid-lowering agents are used in combination to lower the cholesterol at different sites. ■■ Research is being done on the effects of blocking the endocannabinoid system, resulting in weight loss, improved lipid profiles and decreased proinflammatory and prothrombotic states. Questions have not been answered about the safety or effectiveness of drugs that block this system. Knowing your strengths and weaknesses helps you to study more effectively. Take a PrepU Practice Quiz to find out how you measure up!

ONLINE RESOURCES

An extensive range of additional resources to enhance teaching and learning and to facilitate understanding of this chapter may be found online at the text’s accompanying website, located on thePoint at http://thepoint.lww.com. These include Watch and Learn videos, Concepts in Action animations, journal articles, review questions, case studies, discussion topics and quizzes.

WEB LINKS

Healthcare providers and students may want to consult the following Internet sources: www.heartfoundation.org.au Information on research, alternative methods of therapy and pharmacology. www.heartfoundation.org.nz Information on research, alternative methods of therapy and pharmacology. www.medsafe.govt.nz/profs/puarticles/ simvastinsept2011.htm New Zealand Medicines and Medical Devices Authority. BIBLIOGRAPHY Australian Institute of Health and Welfare (AIHW). (2010). Cardiovascular disease mortality: Trends at Different Ages . Cat. no. CVD 47. Canberra: AIHW. Ayer, J. G. & Sholler, G. F. (2012). Cardiovascular risk factors in Australian children: Hypertension and lipid abnormalities. Australian Prescriber, 35(2) , 51–55. Colquhoun, D. (2008). How to treat hypercholesterolaemia. Australian Prescriber, 31 , 119–122. Farrell, M. & Dempsey, J. (2014). Smeltzer & Bare’s Textbook of Medical-Surgical Nursing (3rd edn). Sydney: Lippincott Williams & Wilkins. Goodman, L. S., Brunton, L. L., Chabner, B. & Knollmann, B. C. (2011). Goodman and Gilman’s Pharmacological Basis of Therapeutics (12th edn). New York: McGraw-Hill. Hamilton-Craig, I., Kostner, K. M., Woodhouse, S. & Colquhoun, D. (2012). Use of fibrates in clinical practice: Queensland Lipid Group consensus recommendations. International Journal of Evidence- Based Healthcare, 10(3) , 181–190. Hossain, P., Kawar, B. & El Nahas, M. (2007). Obesity and diabetes in the developing world—A growing challenge. New England Journal of Medicine, 356 , 213–215. Kastelen, J. P., Akdim, F., Stroes, E. & Zwinderman, A. H. (2008). Simvastatin with or without ezetimibe in familial hypercholesterolemia. New England Journal of Medicine, 358, 1431–1443. McKenna, L. (2012). Pharmacology Made Incredibly Easy (1st Australian and New Zealand edn). Sydney: Lippincott Williams & Wilkins. McKenna, L. & Mirkov, S. (2014). McKenna’s Drug Handbook for Nursing and Midwifery (7th edn). Sydney: Lippincott Williams & Wilkins.