Safety in numbers 1: Essential numerical and scientific principles underpinning medication dose calculation

Registered nurses spend up to 40% of their professional clinical practice engaged in the art and science of medication dosage calculation problem-solving (MDC-PS). In advancing this patient safety critical discipline it is our position that as a profession we must first situate MDC-PS within the context of the wider features of the nursing numeracy, medicines management and clinical pharmacokinetic domains that inform its practice. This paper focuses on the essential relationship between numeracy, healthcare numeracy, medicines management, pharmacokinetics and MDC-PS. We present a taxonomy of generic numerical competencies for the pre-registration curriculum, with examples of essential medication dosage calculation requirements mapped to each skills domain. This is followed by a review of the symbols and measurement units that represent essential components of calculation competence in healthcare and medicines management practice. Finally we outline the fundamental pharmacokinetic knowledge that explains how the body deals with medication and we illustrate through clinical correlations why numeric and scientific knowledge and skills must be mastered to ensure safe dosage calculation and medicines management practice. The findings inform nurse education practice via advancing our understanding of a number of issues, including a unified taxonomy of generic numerical competencies mapped to the 42 revised UK Nursing and Midwifery Council (NMC) Essential Skills Clusters (NMC, 2010a; NMC, 2010b).