Drug Calculations for Nurses: A step-by-step approach, Fourth Edition, 4th Edition (Paperback) book cover

Drug Calculations for Nurses

A step-by-step approach, Fourth Edition, 4th Edition

By Robert Lapham


334 pages | 52 B/W Illus.

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The administration of drug treatments in hospitals has become increasingly complex. It sometimes involves potent drugs that may be fatal if administered incorrectly. The ability to perform drug calculations accurately is therefore paramount to prevent placing patients at risk.

Drug Calculations for Nurses: A Step-by-Step Approach teaches healthcare professionals how to perform drug calculations with confidence and competence. It provides step-by-step guidance to carry out accurate drug calculations, with units and drug strengths clearly explained.

This bestselling pocket-size book begins with the basic mathematical skills required to perform calculations, including tips on estimating answers. It then covers drug strengths and concentrations, dosage calculations, IV infusion therapies, and pharmacodynamics and pharmacokinetics. Two separate chapters focus on children and the elderly, addressing specific challenges encountered in these populations.

Helpful worked examples, key points, and objectives are included in every chapter. Useful tables with common prescription abbreviations, estimation of renal function, and body surface area estimates are easily accessible through the appendices.

This new edition comes with an online pre-test enabling readers to benchmark their knowledge. Specific weaknesses can then be identified and addressed in the printed book. Also included is a revision test that allows readers to assess their ability to perform drug calculations after completing the book.


"…covers everything nurses need to know to administer medications … The step-by-step approach includes examples of how to work problems. In addition, there are practice tests online, as well as tips and key points to help students understand math concepts. Some pharmacological concepts are also covered, such as pharmacodynamics and pharmacokinetics."’

—Carol Agana, MNSc, CNP, APRN, University of Arkansas in Doody’s Book Reviews

Table of Contents




Arithmetic Symbols

Basic Maths

Rules of Arithmetic

Fractions and Decimals

Roman Numerals

Powers or Exponentials

First Principles

Before We Start

Sense of Number and the Use of Calculators or Formulae

Estimation of Answers

The ‘One Unit’ Rule

Checking Your Answer – Does it Seem Reasonable?

Putting it All Together

Minimizing Errors

Percent and Percentages


Percent and Percentages

Converting Fractions to Percentages and Vice Versa

Converting decimals to Percentages and Vice Versa

Calculations Involving Percentages

Drug Calculations Involving Percentages

How to Use the Percentage Key on Your Calculator

Units and Equivalences


SI Units

Prefixes Used in Clinical Practice


Conversion from One Unit to Another

Guide to Writing Units

Moles and Millimoles


What are Moles and Millimoles?

Millimoles and Micromoles

Drug Strengths or Concentrations


Percentage Concentration mg/mL concentrations

‘1 In …’ Concentrations or Ratio Strengths

Parts Per Million (ppm)

Drugs Expressed in Units


Dosage Calculations


Calculating the Number of Tablets or Capsules Required

Drug Dosages Based on Patient Parameters

Ways of Expressing Doses

Calculating Drug Dosages

Displacement Values or Volumes

Prescriber Calculations

Infusion Rate Calculations


Drip Rate Calculations (drops/min)

Conversion of Dosages to mL/hour

Conversion of mL/hour Back to a Dose

Calculating the Length of Time for IV Infusions


Intravenous Therapy and Infusion Devices

IV Infusion Therapy


Infusion Devices

Infusion Device Classification

Action and Administration of Medicines

Action and Administration of Medicines


Pharmacokinetics and Pharmacodynamics

Administration of Medicines

Promoting the Safer use of Injectable Medicines

Children and Medicines


Drug Handling in Children


Routes of Administration of Drugs

Practical Implications

Useful Reference Books

Approximate Values Useful in the Calculation of Doses in Children

The Elderly and Medicines


Drug Handling in the Elderly

Specific Problems in the Elderly

General Principles

Sources and Interpretation of Drug Information


Sources of Drug Information

The Internet

Summary of Product Characteristics (SPC)

Revision Test

Section One: Basics

Per cent and Percentages

Units and Equivalences

Drug Strengths or Concentrations

Dosage Calculations

Infusion Rate Calculations

Compare Your Scores

Answers to Problems

Answers to Problems Set in Chapters

Per Cent and Percentages

Units and Equivalences

Moles and Millimoles

Drug Strengths or Concentrations

Dosage Calculations

Infusion Rate Calculations

Action and Administration of Medicine


Body Surface Area (BSA) Estimates

Weight Conversion Tables

Height Conversion Tables

Calculation of Body Mass Index (BMI)

Estimation of Renal Function

Abbreviations Used in Prescriptions

About the Author

Robert Lapham, BPharm, Clin Dip Pharm, clinical pharmacist, Sunderland, UK

Subject Categories

BISAC Subject Codes/Headings:
MEDICAL / Health Care Delivery
MEDICAL / Nursing / General
MEDICAL / Reproductive Medicine & Technology