Chapter 11: Drug Labels, Dosage Calculations & Math

Drug Labels, Dosage Calculations & Math establishes a systematic approach to math computations to minimize the risk of medication errors, emphasizing the necessity of performing three distinct label checks throughout the drug administration process. The text identifies the metric system as the international standard for dosage determination, though it also covers the conversion of English household measurements which are still common in domestic settings. Core calculation methodologies are detailed, including the basic formula, ratio and proportion through fractional equations, and dimensional analysis, which is particularly useful for complex multi-step conversions. Mastery of interpreting drug labels is highlighted, requiring the identification of trade and generic names, dosage strengths, and expiration dates while remaining vigilant for look-alike or sound-alike medications. The chapter outlines specific rounding rules for various drug forms, noting that while scored tablets may be split, sustained-release and enteric-coated preparations must remain whole to preserve their long-acting properties. For specialized populations, individualized dosing strategies based on body weight and body surface area are explored, utilizing tools like the West nomogram and the square root method. Furthermore, the text addresses the nuances of drug reconstitution, the use of dedicated syringes for insulin and heparin, and the technical requirements for different administration routes, including enteral feeding tubes and parenteral injections. Finally, advanced intravenous therapy concepts are discussed, such as calculating flow rates in drops per minute or milliliters per hour, managing electronic infusion devices, and utilizing patient-controlled analgesia (PCA) to maintain uniform therapeutic drug levels.