The Effect of Drug Concentration Expression on Epinephrine Dosing Errors: A Randomized Trial

Ann Intern Med. 2008 Jan 1;148(1):11-4. doi: 10.7326/0003-4819-148-1-200801010-00003.


Background: The expression of drug concentration as a ratio may cause dosing errors.

Objective: To examine the effect of ratio expressions on drug administration.

Design: Randomized, blinded, controlled study.

Setting: Simulation center in an urban hospital.

Participants: 28 physicians.

Intervention: Participants managed a simulated pediatric acute anaphylaxis scenario by using epinephrine ampules labeled with mass concentration (1 mg in 1 mL) or a ratio (1 mL of a 1:1000 solution).

Measurements: The amount of epinephrine given and the time taken to administer it.

Results: Compared with providers using ampules with mass concentration labels, those using ratio labels gave more epinephrine (adjusted mean dose, 213 microg above target [95% CI, 76.4 to 350.1 microg]; P = 0.003), and took longer to do so (adjusted mean delay, 91 seconds, [CI, 61.0 to 122.1 seconds]; P < or = 0.0001).

Limitations: Performance in simulated scenarios may not reflect clinical practice. In reality, ampule labels provide both expressions of concentration.

Conclusion: The use of ratios to express drug concentration may be a source of drug administration error. Patient safety might be improved by expressing drug concentrations exclusively as mass concentration.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Anaphylaxis / drug therapy
  • Child
  • Clinical Protocols
  • Drug Labeling / standards*
  • Epinephrine / administration & dosage*
  • Female
  • Humans
  • Male
  • Medication Errors*
  • Patient Simulation
  • Single-Blind Method
  • Time Factors
  • Vasoconstrictor Agents / administration & dosage*


  • Vasoconstrictor Agents
  • Epinephrine