In severe cases of allergy attacks, adrenaline (epinephrine) shots are given. Although injectors such as Epi-Pens are available for consumer use, doctors use a solution stored in salt water in glass ampoules, in which the amount of adrenaline contained in the ampoule is usually expressed as both a dose (1 mg of the drug per 1 mL of salt water) and a ratio (1 part drug for every 1000 parts of salt water) on the label.

A new study revelead, however, that in cases where the amount of adrenaline is expressed as a ratio, doctors tend to overdose their patients.

All but 2 doctors out of 14 whose ampoules with labels that expressed the amount of adrenaline as a ratio overdosed their patients. Because they had to figure out how much drug to give, the doctors using ampoules labeled with a ratio also took about 1.5 minutes longer to give it.

The ratio requires doing arithmetic to figure out how much drug to give. Therefore, doctors understand doses much better (and quicker) than ratios. Dr Daniel Wheeler at the University of Cambridge concluded from his research that having to do extra calculations to figure out how much adrenaline to give a person in an emergency might lead to the errors and delays which are common in administering the drug.

Given these observations, the researchers suggest that labels expressing drug concentrations exclusively as doses would be much better than that which indicates the ratios, or both the ratios and doses.

Image: Epinephrine Credit: John L. Bezzant, M.D.