LETTERS

Intensive teaching of drug calculation skills: the earlier the better There is now a great deal of evidence that doctors experience great difficulties when calculating drug doses. Six questionnaire studies published over the past 20 years have shown that when determining the correct volume of a drug solution to administer, doctors struggle when converting ratios and percentages.1e5 Despite recent evidence that these ways of expressing the concentration of drug solutions result in clinical errors,6 ratios and percentages continue to appear on drug ampoule labels