Background Calculating a paediatric dose is complex due to a variety of parameters influencing the dose and therefore error prone, ultimately resulting in incorrect dosing, lack of efficacy and/or adverse effects. The devel-opment and implementation of a paediatric dosing cal-culator could reduce calculating errors.

Objectives 1. To develop a clinical decision tool for cal-culating an individual paediatric dose, using the compre-hensive Dutch paediatric formulary as dosing reference.

2. To show a 50% reduction of calculation errors by estab-lishing an individualised paediatric dose through a paedi-atric dosing module.

Methods The Paediatric Dosing Calculator consists of a calculation interface which integrates the dosing rec-ommendations of the Dutch paediatric Formulary with clinical patient variables, thus resulting in an individual recommended dose. After establishing the functional requirements and risk minimization measures the dosing calculator was developed by using a test-retest approach. The alfa version was validated by performing 2 calcula-tions for an aselect sample of 230 drugs of the formulary. Two groups of healthcare professionals were presented with 15 cases for which they were asked to calculate a dose. One group (n=37) was instructed to calculate with conventional tools i.e. a mathematical calculator and the dosing recommendations as listed in the Dutch Paediat-ric Formulary. The second group (n=36) was instructed to use the integrated paediatric dosing calculator interface. The time for the calculating tasks was limited to 2 min-utes per case as to mimic the stressful circumstances of daily practice. The% of calculating errors was compared between groups.

Results Of the 460 test calculations of the first calculator version 5% contained a calculation error. After analysing, correction and re-testing an error-free beta version was launched. Using the calculator interface resulted in a 35% reduction of calculating errors compared to manual cal-culations (18,7%/(range 0%–83%) vs 28,4% (range 9%–61% ), respectively.

Conclusion We successfully developed a web-based dose calculator. The use of this calculator appears to re-duce dosing errors by approximately one third. Health-care providers may benefit from using the calculator in-terface provided that they carefully enter and select the parameters required.