McKenna's Pharmacology, 2e

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P A R T 1  Introduction to nursing pharmacology

paediatric doses. This is a good practice when working with small children. Body surface area The surface area of a child’s body may also be used to determine the approximate dose that should be used. To do this, the child’s surface area is determined with the use of a nomogram (Figure 5.1). The height and weight of the child are taken into consideration in this chart. The following formula is then used: This method is more precise than the formula methods, but you have to have a nomogram available to determine the surface area. Milligrams/kilograms of body weight When a safe and effective paediatric dose has been estab- lished, the orders for the drug dose are often written in milligrams/kilograms. This method of prescribing takes into consideration the varying weights of children and the need for a higher dose of the drug when the weight increases. For example, if a child with postoperative nausea is to be treated with ondansetron the recom- mended dose is 0.1 mg/kg by intravenous injection. If the child weighs 22 kg, the dose for this child would be 0.1 mg/kg × 22 kg, or 2.2 mg. If a child weighed only 8 kg, the recommended dose would be 0.1 mg/kg × 8 kg, or 0.8 mg. Note that this is only the dosage for the drug. Before administration, the volume required still needs to be calculated. The established guidelines allow the drug to be used safely within a large range of children. Some adult doses will also be written in this way. This is usually found in drugs with a small margin of safety or high potential for toxic effects, such as antineoplastic drugs. CHAPTER SUMMARY ■■ The metric system is the most widely used system of measure. All drugs are dispensed in quantities defined using the metric system. ■■ Children require doses of most drugs different to those of adults due to the way their bodies handle drugs and the way that drugs affect their tissues and organs. ■■ Paediatric doses are based on body surface area, child’s dose = surface area (m 2 ) 1.73 × average adult dose

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. BIBLIOGRAPHY Atik, A. (2013). Adherence to the Australian National Inpatient Medication Chart: the efficacy of a uniform national drug chart on improving prescription error. Journal of Evaluation in Clinical Practice, 19(5) , 769–772. Boyer, M. J. (2009). Math for Nurses: A Pocket Guide to Dosage Calculation and Drug Preparation . Philadelphia: Lippincott, Williams & Wilkins. Brotto, V. & Rafferty, K. (2012). Clinical Dosage Calculations for Australia & New Zealand. Melbourne: Cengage. Craig, G. (2008). Clinical Calculations Made Easy. Philadelphia: Lippincott Williams & Wilkins. DeCastillo, S. & Werner-McCullough, M. (2007). Calculating Drug Dosages: An Interactive Approach (7th edn). Philadelphia: Davis. Dempsey, J., Hillege, S. & Hill, R. (2014). Fundamentals of Nursing and Midwifery: A Person-centred Approach to Care (2nd Australian and New Zealand edn). Sydney: Lippincott Williams & Wilkins. Gatford, J. D. & Phillips, N. (2011). Nursing Calculations (8th edn). Edinburgh: Churchill Livingstone. Morrison, G. (2007). Drug dosing in the intensive care unit: The patient with renal failure. In Rippe, J. M., Irwin, R. S. & Fink, M. P. (Eds.), Intensive Care Medicine (3rd edn) (pp. 951–986). Boston: Little, Brown. Ogden, S. (2007). Calculation of Drug Dosages (7th edn). St Louis: Mosby. Springhouse, Corp. 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. Tzeng, H-M., Yin, C. & Schneider, T. E. (2013). Medication error- related issues in nursing practice. MEDSURG Nursing , 22(1) , 13–50.

which requires the use of a nomogram, and milligrams per kilogram of body weight.