December  22, 2025

Welcome again to UH EMS-I’s Pharmacy Phriday. In this edition, we’ll focus on the administration of weight-based medications in the pre-hospital field. It is unfortunate to read and hear the frequency of inaccurate medication administrations due to calculation errors. Many studies and research have been done regarding reducing such errors, with various recommendations. 

“Performing mathematical dosing calculations at the bedside is an area at very high risk for error. EMS agencies and providers should utilize dose-derivation strategies that avoid use of calculations at the patient side. Tools that provide pre-calculated weight-based dosing and preclude the need for calculation by EMS providers can reduce dosing errors.”1 A tool provided by our UH partners this past year, the OneDose™ Protocol Management Tool, can be of great assistance to the provider in these high-stress environments. 

One of the first steps in making weight-based medication calculations is converting a patient’s weight from the customary pound unit to the metric kilogram unit. The OneDose app can make this conversion for you by opening the “patient input” bar at the bottom of the screen and making one of the following entries: 

1. Enter the weight in pounds. 

2. Use the slide bar estimator based on the patient’s age. 

3. Select the corresponding color from the Broselow™ Pediatric Emergency Tape (Note: there are also options for the small, medium, or large adult at the bottom of the list). 

A provider recently reached out to share an experience where they had difficulty with the application during a call. It is extremely important that providers be familiar and practice use with the application in training scenarios to ensure efficiency at stressful times. For a tutorial on the weight conversion feature of the OneDose app, click here. 

In using the OneDose app, it is important to note a few other items: 

• Open the application and update it at the beginning of every shift. 

• A “Remember Me” has been added to the login feature to speed access, as well as an “Auto Login” feature. 

• Remember, once the patient input has been saved, the application makes the drug calculations within the protocols for you. Simply tap on the “Calculation” tab within each algorithm. 

• After each patient encounter, “End Interaction” to reset the application for the next patient encounter. This can be found on the right of the “Patient Input” bar at the bottom of the screen.  

• Regarding rounding, the decimal place can be turned off and on in the “General Settings” of the application. 

In cases where access to the app is not available, the provider may need to rely on making the calculations themselves. As a refresher, let’s review the formulas that can be helpful in making the weight conversion from pounds to kilograms. 

The first is the official conversion formula: weight in lbs./ 2.2 = weight in kg. If a calculator is available, that obviously makes this much easier. Remember the standard rule for rounding: “5 and up, round up.” Typically, the weight is rounded to the “one” position. For pediatric patients, it is sometimes recommended to round to the tenth’s position. An example of this formula at work follows: 

Example: 180 lb. patient/ 2.2 = 81.818181…. 

Rounded off, the patient’s weight is converted to 82 kg 

An alternative formula, though not exact, is as follows: The patient’s weight in lbs./ 2, then subtract 10% from that number = weight in kg. An example of this at work follows: 

Example: 180 lb. patient/ 2 = 90 

90 x 10% = 9 

90 – 9 = 81 kg 

Due to the increased chance in errors, any drug calculation should be cross-checked by another team member or medical direction, if necessary. 

As an exercise, convert the following patient weights using the various methods from above: 

1. Your patient weighs 225 lbs. Using the OneDose app, this equals _______ kg. 

2. Your patient weighs 150 lbs. Using the alternative formula, this patient weighs _____ kg. 

3. Your patient weighs 35 lbs. Once again, using the OneDose app this equals ________ kg. 

Happy Holidays, and until next time, stay safe! 

Sincerely, 

The UH EMS-I Team 

University Hospitals