Pediatric Dosing¶
Overview¶
Pediatric dosing requires extra care and precision. Children are not simply small adults — their physiology, metabolism, and organ function differ significantly, making accurate weight-based calculations critical to their safety.
Errors in pediatric dosing are among the most serious medication errors in clinical practice.
Key Differences from Adult Dosing¶
| Factor | Adult | Pediatric |
|---|---|---|
| Dose basis | Fixed dose or mg/kg | Almost always mg/kg |
| Weight unit | kg | kg (verify carefully) |
| Rounding | Nearest tenth | Nearest hundredth often required |
| Max dose | Sometimes applies | Almost always applies |
| Double check | High alert meds | All medications |
| Concentration | Standard | Often more dilute |
Age and Weight Classifications¶
Pediatric Age Groups
| Group | Age Range |
|---|---|
| Neonate | Birth to 28 days |
| Infant | 1 month to 1 year |
| Toddler | 1 to 3 years |
| Child | 3 to 12 years |
| Adolescent | 12 to 18 years |
Dosing guidelines and normal ranges differ between these groups. Always verify against age-appropriate references.
Weight Verification¶
Always Verify Pediatric Weight
Before calculating any pediatric dose:
- Obtain a measured weight — never estimate
- Weigh in kg — if scale reads lb, convert
- Verify the weight is recent and accurate
- For neonates, use weight in grams if specified
- Have a second nurse verify the weight
Neonatal Weight¶
Neonates are often dosed by weight in grams rather than kg.
Example: A neonate weighs 3.2 kg. Express in grams:
Standard Pediatric Calculation¶
Example 1: Order: amoxicillin 25 mg/kg orally every 8 hours Patient: child weighing 20 kg Stock: 250 mg/5 mL
Step 1 — dose per administration: [20 \cancel{\text{ kg}} \times \frac{25 \text{ mg}}{1 \cancel{\text{ kg}}} = 500 \text{ mg}]
Step 2 — volume: [\frac{500 \cancel{\text{ mg}}}{1} \times \frac{5 \text{ mL}}{250 \cancel{\text{ mg}}} = 10 \text{ mL}]
Maximum Dose in Pediatrics¶
Example 2: Order: paracetamol 15 mg/kg orally every 6 hours Maximum single dose: 500 mg Patient: child weighing 40 kg Stock: 250 mg/5 mL
Step 1 — calculated dose: [40 \cancel{\text{ kg}} \times \frac{15 \text{ mg}}{1 \cancel{\text{ kg}}} = 600 \text{ mg}]
600 mg exceeds maximum of 500 mg — use 500 mg
Step 2 — volume: [\frac{500 \cancel{\text{ mg}}}{1} \times \frac{5 \text{ mL}}{250 \cancel{\text{ mg}}} = 10 \text{ mL}]
Daily Dose Divided¶
Example 3: Order: penicillin V 50 mg/kg/day orally divided every 6 hours Patient: child weighing 24 kg Stock: 125 mg/5 mL
Step 1 — total daily dose: [24 \cancel{\text{ kg}} \times \frac{50 \text{ mg}}{1 \cancel{\text{ kg}}} = 1200 \text{ mg/day}]
Step 2 — single dose (every 6 hours = 4 doses/day): [1200 \div 4 = 300 \text{ mg per dose}]
Step 3 — volume per dose: [\frac{300 \cancel{\text{ mg}}}{1} \times \frac{5 \text{ mL}}{125 \cancel{\text{ mg}}} = 12 \text{ mL}]
Verifying a Safe Dose Range¶
Many pediatric references provide a safe dose range (minimum and maximum mg/kg). Always verify the ordered dose falls within this range.
Safe Dose Range Check
Safe dose range: 20-40 mg/kg/day Ordered dose: 30 mg/kg/day Patient weight: 15 kg
Step 1 — calculate minimum safe dose: [15 \text{ kg} \times 20 \text{ mg/kg} = 300 \text{ mg/day}]
Step 2 — calculate maximum safe dose: [15 \text{ kg} \times 40 \text{ mg/kg} = 600 \text{ mg/day}]
Step 3 — calculate ordered dose: [15 \text{ kg} \times 30 \text{ mg/kg} = 450 \text{ mg/day}]
450 mg/day falls between 300 and 600 mg/day ✅ The dose is within the safe range.
Out of Range — Do Not Administer
If the ordered dose falls outside the safe range:
- Do not administer
- Recheck your calculation
- Verify the patient weight
- Contact the prescriber immediately
- Document your actions
Small Volume Accuracy¶
Use an Oral Syringe for Small Volumes
Pediatric doses are often less than 5 mL. Always use a calibrated oral syringe for volumes under 5 mL — medicine cups are not accurate enough for small volumes.
For volumes under 1 mL, use a 1 mL syringe graduated in 0.01 mL increments.
Practice Problems¶
Problem 1
Order: ibuprofen 10 mg/kg orally Patient: child weighing 25 kg Stock: 100 mg/5 mL How many mL?
Answer
Step 1 — dose: [25 \cancel{\text{ kg}} \times \frac{10 \text{ mg}}{1 \cancel{\text{ kg}}} = 250 \text{ mg}]
Step 2 — volume: [\frac{250 \cancel{\text{ mg}}}{1} \times \frac{5 \text{ mL}}{100 \cancel{\text{ mg}}} = 12.5 \text{ mL}]
Problem 2
Order: amoxicillin 40 mg/kg/day orally divided every 12 hours Patient: child weighing 18 kg Stock: 400 mg/5 mL How many mL per dose?
Answer
Step 1 — total daily dose: [18 \cancel{\text{ kg}} \times \frac{40 \text{ mg}}{1 \cancel{\text{ kg}}} = 720 \text{ mg/day}]
Step 2 — single dose: [720 \div 2 = 360 \text{ mg per dose}]
Step 3 — volume: [\frac{360 \cancel{\text{ mg}}}{1} \times \frac{5 \text{ mL}}{400 \cancel{\text{ mg}}} = 4.5 \text{ mL}]
Problem 3
Order: paracetamol 15 mg/kg orally Maximum single dose: 500 mg Patient: child weighing 38 kg Stock: 250 mg/5 mL How many mL?
Answer
Step 1 — calculated dose: [38 \cancel{\text{ kg}} \times \frac{15 \text{ mg}}{1 \cancel{\text{ kg}}} = 570 \text{ mg}]
570 mg exceeds max of 500 mg — use 500 mg
Step 2 — volume: [\frac{500 \cancel{\text{ mg}}}{1} \times \frac{5 \text{ mL}}{250 \cancel{\text{ mg}}} = 10 \text{ mL}]
Problem 4
Safe dose range: 10-20 mg/kg/day Order: 15 mg/kg/day divided every 8 hours Patient: child weighing 30 kg Is the dose safe?
Answer
Minimum safe dose: [30 \text{ kg} \times 10 \text{ mg/kg} = 300 \text{ mg/day}]
Maximum safe dose: [30 \text{ kg} \times 20 \text{ mg/kg} = 600 \text{ mg/day}]
Ordered dose: [30 \text{ kg} \times 15 \text{ mg/kg} = 450 \text{ mg/day}]
450 mg/day is between 300 and 600 mg/day ✅ Dose is safe.
Single dose (every 8 hours = 3 doses/day): [450 \div 3 = 150 \text{ mg per dose}]
Problem 5
Order: morphine 0.05 mg/kg IV Patient: child weighing 22 kg Stock: 1 mg/mL How many mL? Round to nearest hundredth.
Answer
Pediatric Medication Safety
Every pediatric medication administration requires an independent double check by a second nurse. This is not optional — it is a professional and legal requirement in most clinical settings.
The double check must be independent — the second nurse calculates from scratch without seeing your answer.