McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 3 1 Adrenergic blocking antagonists

CHAPTER SUMMARY ■■ Adrenergic blocking agents, or sympatholytic drugs, lyse, or block, the effects of the sympathetic nervous system (SNS). ■■ Both the therapeutic and the adverse effects associated with these drugs are related to their blocking of the normal responses of the SNS. ■■ The alpha- and beta-adrenergic blocking agents block all of the receptor sites within the SNS, which results in lower blood pressure, slower pulse and increased renal perfusion with decreased renin levels. These drugs are indicated for the treatment of essential hypertension. They are associated with many adverse effects, including lack of bronchodilation, cardiac suppression and diabetic reactions. ■■ Selective adrenergic blocking agents have been developed that, at therapeutic levels, have specific affinity for alpha- or beta-receptors or for specific alpha 1 -, beta 1 -, or beta 2 - receptor sites. This specificity is lost at levels higher than the therapeutic range. ■■ Alpha-adrenergic drugs specifically block the alpha- receptors of the SNS. At therapeutic levels, they do not block beta-receptors. ■■ Non-specific alpha-adrenergic blocking agents are used to treat phaeochromocytoma, a tumour of the adrenal medulla. ■■ Alpha 1 -selective adrenergic blocking agents block the postsynaptic alpha 1 -receptor sites, causing a decrease in vascular tone and a vasodilation that leads to a fall in blood pressure without the reflex tachycardia that occurs when the presynaptic alpha 2 -receptor sites are also blocked. ■■ Beta-blockers are drugs used to block the beta- receptors within the SNS. These drugs are used for a wide range of conditions, including hypertension, stage fright, migraines, angina and essential tremors. ■■ Blockade of all beta-receptors results in a loss of the reflex bronchodilation that occurs with sympathetic stimulation. This limits the use of these drugs in individuals who smoke or have allergic or seasonal rhinitis, asthma or COPD. ■■ Beta 1 -selective adrenergic blocking agents do not block the beta 2 -receptors that are responsible for bronchodilation and therefore are preferred in people with respiratory problems.

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 Home page of the Heart Foundation Australia. Information, support groups, diet, exercise and research information on hypertension and other cardiovascular diseases. www.heartfoundation.org.nz Home page of the National Heart Foundation New Zealand. Information, support groups, diet, exercise and research information on hypertension and other cardiovascular diseases. Barrett, K. E. & Ganong, W. F. (2010). Ganong’s Review of Medical Physiology (23rd edn). New York: McGraw-Hill. Boyce, B. A. B. & Yee, B. H. (2012). Incidence and severity of phlebitis in patients receiving peripherally infused amiodarone. Critical Care Nurse , 32(4) , 27–34, 71. Campbell, T. J. (2005). Amiodarone. Australian Prescriber , 28 , 150–154. Elsik, M. & Krum, H. (2007). Should beta blockers remain first-line drugs for hypertension? Australian Prescriber , 30 , 5–7. Farrell, M. & Dempsey, J. (2014). Smeltzer & Bare’s Textbook of Medical-Surgical Nursing (3rd edn). Sydney: Lippincott Williams & Wilkins. Fonseca, V. A. (2010). Effects of beta-blockers on glucose and lipid metabolism. Current Medical Research & Opinion , 26(3) , 615–629. 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. Guyton, A. & Hall, J. (2011). Textbook of Medical Physiology (12th edn) . Philadelphia: Saunders Elsevier. 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. Nelson, M. (2010). Drug treatment of elevated blood pressure. Australian Prescriber , 33 , 108–112. BIBLIOGRAPHY

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