Doctors are confused when calculating drug concentrations
Doctors appear to be confused by the ways in which drug concentrations are expressed.
Researchers conducted an online
test of subscribers to doctors.net.uk and invited responses to six multiple-choice questions about three drug
solutions used in common clinical scenarios. As examples they chose adrenaline
(expressed as a ratio), lidocaine (expressed as a percentage) and atropine
(expressed in mg/ml). Respondents had particular trouble calculating
the amount of drug contained in a vial labelled as a percentage (eg,
1% w/v). A third of the 2,975 participants got this calculation wrong.
Respondents fared better when labels were expressed as mass per unit
volume — 93.1 per cent were able to identify the correct concentration.
However, only 65.5 per cent went on to calculate the correct amount of
solution needed when presented with a hypothetical clinical scenario.
The researchers suggest drug solutions should be labelled as mass per
unit volume. |
The
Pharmaceutical Journal
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