Why changing epinephrine label from ratio expression to mass dose won't eliminate errors

Failure to recognize and treat anaphylaxis quickly and dose calculation errors are more significant problems than how an epinephrine vial or ampule is labeled

By David Johnson

Effective May 1, 2016 single entity drugs, like epinephrine, will no longer be labeled as a ratio. This also pertains to isoproterenol and neostigmine. Like most drug dosing, these drugs will be expressed as a mass dose in mg/mL. This change is intended to resolve an ongoing concern about medication dosing errors.

The biggest likely impact for prehospital providers is on epinephrine dosing and to try to avoid administering epinephrine 1/1,000 at the 1/10,000 mL dose. Epinephrine, previously labeled 1/1,000 will be become 1 mg/mL; 1/10,000 will be 0.1 mg/mL.

This change will not remove ratios for multiple drug entities such as lidocaine with epinephrine. 

Epinepherine administration and dosing errors
This solution, although a good one, may still not eliminate dosing errors (1mg/mL vs 0.1mg/mL). Even before this change, auto-injectors (e.g., EpiPen) have been used because of their simplicity and accuracy. They also have their downsides.

The first has to do with the dose of drug available. Auto-injectors, because of their fixed doses (0.15mg and 0.3mg), cannot be precisely tailored to patient weight (0.01mg/kg). And if you believe the European Resuscitation Council the upper dosage range falls short of their recommendation to give 0.5 mg.

There is also a concern about auto-injector cost, the needle being too short to penetrate the patient's muscle, and the needle causing injuries.

Switching from auto-injectors to vials or ampules because of the cost is a potentially a risky option, especially in children as evidenced by Lammers etal. They found in a simulation exercise of anaphylaxis in a child, only 46 percent of EMS responders working in teams of 2, one of whom was a paramedic, gave the correct dosage via the correct route. 

Although available as one of their options, this was not a problem of confusing 1/1,000 vs 1/10,000. The errors had to do with calculating the correct dose using one of several 1/1,000 options — including auto-injectors — and administering IV epinephrine when it was not indicated.

A number of case studies make it clear that this is not a problem exclusive to EMS practitioners. King County EMS (Seattle) has a very good solution that balances cost with safety. They have developed an anaphylaxis kit that includes a 1 mg vial of 1mg/mL epinephrine, syringes, dosing instructions, all contained within a small plastic case. The cost is under $20.

Another equally worrisome and more commonly occurring concern is giving epinephrine for anaphylaxis too late or failing to give it at all. In an abstract(58) presented at the Scientific Meeting of the American College of Allergy, Asthma and Immunology 2012-011-12, El Sanadi et al presented data that only 15 percent of 52 patients with anaphylaxis were treated by EMS practitioners with epinephrine while 81 percent received diphenhydramine, their histamine antagonist of choice. 

Whether epinephrine use was delayed because of an irrational fear of epinephrine or a misunderstanding of the pathophysiology and pharmacology, this is an all too common problem both on the street and in the hospital.

As usual, the solution to all of these problems comes down to proper education and repeated, practical training.

About the author
In addition to his writing, teaching and business responsibilities with Wilderness Medical Associates, Johnson has worked as an emergency physician in Maine and Georgia for over 35 years. His outdoor pursuits have included wilderness canoeing in Canada, climbing and hiking in North and South America, coastal kayaking in Georgia and Maine and sailing around the Atlantic Ocean. Johnson is passionate about curriculum development and teaching.

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