Calculating Paracetamol (P 250) Syrup Volume for Pediatric Patients
To calculate the volume of P 250 syrup (paracetamol 250 mg/5 mL concentration), use the formula: Volume (mL) = [Weight (kg) × Dose (mg/kg) ÷ 50] where the standard pediatric dose is 10-15 mg/kg per dose.
Standard Dosing Formula
The calculation requires three key components:
- Patient weight in kilograms
- Desired dose per kilogram (typically 10-15 mg/kg per dose) 1
- Concentration of the syrup (P 250 = 250 mg per 5 mL = 50 mg/mL)
Step-by-Step Calculation
Step 1: Determine the total milligram dose needed
- Multiply the child's weight (kg) by the dose (mg/kg)
- Standard dosing: 10-15 mg/kg per dose 2, 1
- Maximum single dose: 15 mg/kg 2
- Maximum daily dose: 60 mg/kg/day (divided into 4-6 doses) 1
Step 2: Convert milligrams to milliliters
- Divide the total mg dose by 50 (since P 250 contains 50 mg per mL)
- Formula: mL = (Weight in kg × mg/kg dose) ÷ 50
Step 3: Round appropriately
- For paracetamol syrup, rounding by 5% is acceptable for ease of home administration 2
- Round to the nearest 0.5 mL or 1 mL for practical measurement
Practical Examples
Example 1: 10 kg child at 15 mg/kg dose
- Total dose = 10 kg × 15 mg/kg = 150 mg
- Volume = 150 mg ÷ 50 mg/mL = 3 mL
Example 2: 5 kg infant at 10 mg/kg dose
- Total dose = 5 kg × 10 mg/kg = 50 mg
- Volume = 50 mg ÷ 50 mg/mL = 1 mL
Example 3: 20 kg child at 15 mg/kg dose
- Total dose = 20 kg × 15 mg/kg = 300 mg
- Volume = 300 mg ÷ 50 mg/mL = 6 mL
Dosing Frequency and Maximum Limits
- Dosing interval: Every 4-6 hours as needed 1
- Maximum frequency: 4-6 doses per 24 hours 1
- Maximum daily dose: 60 mg/kg/day (not to exceed 4 grams/day in older children) 1, 3
Critical Safety Considerations
Avoid hepatotoxicity by adhering to maximum doses:
- Single doses exceeding 10 times the recommended dose (>150 mg/kg) are potentially toxic 1
- Chronic exposures greater than 140 mg/kg/day for several days carry risk of serious hepatotoxicity 1
- The therapeutic dose of 10-15 mg/kg is remarkably well tolerated with few side effects 1, 4
Common pitfall: Confusing the concentration—P 250 means 250 mg per 5 mL (not per 1 mL), so always divide by 50 mg/mL when calculating volume 5.