Background: It is essential for health-care professionals to calculate drug doses accurately. Previous studies have demonstrated that many hospital doctors were unable to accurately convert dilutions (e.g. 1:1000) or percentages (e.g. percentage w/v) of drug concentrations into mass concentrations (e.g. mg/mL).
Aims: The aims of the present study were to evaluate the ability of health-care professionals to perform drug dose calculations accurately and to determine their preferred concentration convention when calculating drug doses.
Methods: A selection of nurses, medical students, house surgeons, registrars and pharmacists undertook a written survey to assess their ability to perform five drug dose calculations. Participants were also asked which concentration convention they preferred when calculating drug doses. The surveys were marked then analysed for health-care professionals as a whole and then by subgroup analysis to assess the performance of each health-care-professional group.
Results: Overall, less than 14% of the surveyed health-care professionals could answer all five questions correctly. Subgroup analysis revealed that health-care professionals' ability to calculate drug doses were ranked in the following order: registrars approximately equal to pharmacists > house surgeons > medical students >> nurses. Ninety per cent of health-care professionals preferred to calculate drug doses using the mass concentration convention.
Conclusions: Overall, drug dose calculations were performed poorly. Mass concentration was clearly indicated as the preferred convention for calculating drug doses.