Pediatric Drug Dosing: Weight-Based Calculations in the Field

By Jointra Editorial Team, Certified EMT

The Stakes of Pediatric Dosing

Medication errors occur more frequently in pediatric patients than in adults, and their consequences are more severe. Children have a narrow therapeutic window for many drugs — the difference between an effective dose and a toxic dose is small, and it changes continuously as children grow. Every milligram matters.

The leading causes of pediatric medication errors in EMS: 1. Incorrect weight estimation 2. Calculation errors 3. Concentration errors (10-fold errors with decimal points) 4. Wrong route

Weight Estimation

Drug doses in pediatrics are calculated per kilogram of body weight. Obtaining an accurate weight is rarely possible in the field. Use systematic estimation methods.

Broselow Tape (length-based weight estimation): The most validated and widely used tool in pediatric emergency care. Lay the tape alongside the child from head to heel. The color zone corresponding to the child's length provides:

• Estimated weight in kg
• Pre-calculated drug doses for common emergency medications
• Equipment sizing (ET tube, laryngoscope blade, IO needle)

Age-based formula:

• Infants (0–12 months): Weight (kg) = [Age in months + 9] / 2 (rough estimate)
• Children (1–10 years): Weight (kg) = (Age in years × 2) + 8

When in doubt, use the Broselow tape. When the Broselow tape is unavailable, underestimate rather than overestimate.

Key Emergency Drug Doses

All doses are for reference only — always follow your local protocols.

Epinephrine (cardiac arrest): 0.01 mg/kg IV/IO (1:10,000 concentration); max 1mg. Every 3–5 minutes.

Epinephrine (anaphylaxis): 0.01 mg/kg IM (1:1,000 concentration); max 0.5mg. Anterolateral thigh.

Atropine (bradycardia): 0.02 mg/kg IV/IO; minimum 0.1mg, maximum 0.5mg (child) or 1mg (adolescent).

Adenosine (SVT): 0.1 mg/kg rapid IV push (max first dose 6mg). Double dose if no response: 0.2 mg/kg (max 12mg).

Dextrose (hypoglycemia):

• D25: 2–4 mL/kg (0.5–1g/kg)
• D10: 5–10 mL/kg (same glucose dose)
• Neonates: D10 only (concentrated glucose causes osmotic injury)

Naloxone (opioid reversal):

• <5 years or <20kg: 0.1 mg/kg IV/IO/IM/IN
• ≥5 years or ≥20kg: 2mg IV/IO/IM/IN

Midazolam (seizure/sedation): 0.1–0.2 mg/kg IV/IO; 0.2 mg/kg IM/IN; max 5mg per dose.

Lorazepam (seizure): 0.05–0.1 mg/kg IV/IO; max 4mg.

Normal saline (fluid bolus): 20 mL/kg IV/IO over 5–20 minutes. Reassess after each bolus.

Decimal Point Errors

The most dangerous calculation errors involve misplaced decimal points. Tenfold errors in pediatric drug dosing are well documented and frequently fatal.

Prevention strategies:

• Use the Broselow tape with pre-calculated doses
• Double-check calculations independently
• Repeat back doses verbally before administration
• Use mg/kg — never calculate total dose without confirming the per-kg dose first

Example: Epinephrine for a 10kg child in cardiac arrest = 0.01mg/kg × 10kg = 0.1mg = 1mL of 1:10,000. A decimal error (1mg instead of 0.1mg) is a 10× overdose of a vasopressor.

IO Access in Pediatrics

When IV access is not rapidly achievable in a critically ill pediatric patient, intraosseous (IO) access is the route of choice. All medications and fluids given IV can be given IO. The tibial tuberosity (just below and medial) and distal femur are the most common pediatric IO sites. Dose is identical to IV.

Acceptable time to IO in a pediatric code: 60–90 seconds of failed IV attempts, or immediately in cardiac arrest.