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pediatric-pharmacy/SOPs/Dosing-Verification/SOP-DOSE-001-Weight-Based-Dosing.md

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Standard Operating Procedure: Weight-Based Dosing Verification

Document ID SOP-DOSE-001
Title Weight-Based Dosing Verification for Pediatric Patients
Revision 1.0
Effective Date [DATE]
Author [AUTHOR]
Approved By [APPROVER]
Department Pediatric Pharmacy

1. Purpose

To establish a standardized process for verifying weight-based medication dosing calculations for pediatric patients to ensure safe and accurate dosing and prevent calculation errors.

2. Scope

This procedure applies to all weight-based (mg/kg or mcg/kg) medication orders for pediatric patients from birth through 18 years of age (or institutional age limit). This includes orders for:

  • Inpatient medications
  • Outpatient prescriptions
  • Emergency department medications
  • Chemotherapy (see also SOP-CHEMO-XXX)
  • Investigational medications

3. Responsibilities

3.1 Prescriber

  • Orders medication with appropriate indication
  • Specifies patient weight or references weight in system
  • Includes dosing frequency and duration

3.2 Pharmacist

  • Verifies patient weight is current
  • Calculates dose based on weight
  • Verifies dose is within therapeutic range
  • Verifies maximum dose not exceeded
  • Performs independent double-check for high-alert medications
  • Documents verification

3.3 Pharmacy Technician (if applicable per state law)

  • May perform initial calculation
  • Documents calculation method
  • Flags order for pharmacist verification

4. Definitions

Term Definition
Weight-based dosing Medication dose calculated based on patient body weight (mg/kg or mcg/kg)
Current weight Weight obtained within timeframe per institutional policy (typically 24-72 hours for inpatients)
Maximum dose Upper limit of dose regardless of calculated weight-based dose
Therapeutic range Accepted dosing range for specific indication and patient age
Independent double-check Separate calculation by second pharmacist without viewing first calculation

5. Equipment/Resources Required

  • Pediatric dosing references (Lexicomp, Micromedex, Harriet Lane, etc.)
  • Calculator or verified dosing calculator software
  • Access to current patient weight in medical record
  • Age-appropriate dosing guidelines

6. Procedure

6.1 Patient Information Verification

  1. Confirm Patient Identity

    • Verify patient name and date of birth
    • Confirm medical record number

  2. Obtain Current Weight

    • Check date/time of most recent weight
    • Ensure weight is current per institutional policy:
      • NICU/critical care: Within 24 hours
      • Inpatient: Within 72 hours
      • Outpatient: Within 3-6 months (per age)
    • If weight not current, request updated weight before proceeding
    • Document weight used (value and date obtained)

  3. Verify Weight Units

    • Confirm weight in kilograms (kg)
    • If weight in pounds, convert: kg = pounds ÷ 2.2
    • Round to appropriate decimal places (typically 0.1 kg)

6.2 Dose Calculation

  1. Identify Prescribed Dose

    • Note ordered dose (mg/kg/dose or mg/kg/day)
    • Identify dosing frequency
    • Determine if dose is per dose or per day (total daily dose)

  2. Calculate Individual Dose

    If ordered as mg/kg/dose:
Dose = Weight (kg) × mg/kg/dose

If ordered as mg/kg/day:
Total daily dose = Weight (kg) × mg/kg/day
Individual dose = Total daily dose ÷ number of doses per day

  3. Round Appropriately

    • Follow institutional rounding guidelines
    • Consider available dosage forms
    • Round to measurable quantity
    • Be cautious with high-potency drugs (may require more precision)

6.3 Dose Verification

  1. Reference Check

    • Consult pediatric dosing reference
    • Verify dose is appropriate for:
      • Patient age
      • Indication
      • Renal/hepatic function (if applicable)
    • Check for age-specific restrictions

  2. Range Verification

    • Confirm calculated dose is within therapeutic range
    • Check if dose falls within:
      • Minimum effective dose
      • Maximum recommended dose
    • For unusual doses, document clinical rationale

  3. Maximum Dose Check

    • Identify if medication has maximum dose
    • Verify calculated dose does not exceed adult or absolute maximum
    • Document if maximum dose applied instead of calculated dose

  4. Special Populations

    • Neonates: Check if gestational age affects dosing
    • Obese patients: Determine if ideal body weight should be used
    • Renal/hepatic impairment: Apply dose adjustments if needed

6.4 Independent Double-Check (High-Alert Medications)

For high-alert medications, independent verification required:

  1. First Pharmacist

    • Performs calculation as outlined above
    • Documents result
    • Does not communicate result to second pharmacist

  2. Second Pharmacist

    • Independently obtains patient weight
    • Independently calculates dose
    • Independently verifies range and maximum
    • Compares result with first pharmacist

  3. Discrepancy Resolution

    • If calculations match, proceed
    • If discrepancy identified:
      • Both pharmacists review calculation together
      • Identify source of error
      • Re-calculate if needed
      • Document discrepancy and resolution

6.5 High-Alert Medications Requiring Independent Double-Check

  • Chemotherapy agents
  • Insulin
  • Opioids (for neonates/infants)
  • Concentrated electrolytes
  • Anticoagulants (heparin, enoxaparin)
  • Neuromuscular blocking agents
  • Moderate sedation agents
  • [Add institution-specific medications]

6.6 Documentation

Document in pharmacy system or dosing worksheet:

  • Patient weight and date
  • Dose ordered (mg/kg)
  • Calculated dose
  • Dose rounded/dispensed
  • Maximum dose verification (if applicable)
  • Reference source
  • Pharmacist initials/signature
  • Second pharmacist verification (if applicable)

6.7 Unusual Doses

For doses outside normal range but clinically justified:

  1. Contact prescriber for clarification
  2. Document prescriber confirmation
  3. Document clinical rationale in pharmacy record
  4. Consider additional verification by clinical pharmacist or pharmacy manager
  5. Monitor patient response

7. Examples

Example 1: Amoxicillin for Otitis Media

  • Patient: 2-year-old, weight 12.5 kg
  • Order: Amoxicillin 45 mg/kg/day divided BID
  • Calculation:
    • Total daily dose = 12.5 kg × 45 mg/kg/day = 562.5 mg/day
    • Individual dose = 562.5 mg ÷ 2 = 281.25 mg per dose
    • Rounded dose = 280 mg per dose (or 300 mg if using suspension)
  • Reference check: Within range for acute otitis media (40-80 mg/kg/day)
  • Maximum: Does not apply for amoxicillin

Example 2: Vancomycin for MRSA (with maximum dose)

  • Patient: 14-year-old, weight 75 kg
  • Order: Vancomycin 15 mg/kg IV q12h
  • Calculation:
    • Individual dose = 75 kg × 15 mg/kg = 1,125 mg
  • Maximum dose check: 1,000 mg per dose (typical maximum)
  • Dispense: 1,000 mg (maximum dose applied)
  • Document that maximum dose used instead of calculated dose

8. Quality Checks

  • Monthly review of dosing errors/near misses
  • Audit of weight documentation compliance
  • Review of maximum dose overrides
  • Trending of calculation discrepancies in double-check process

9. Related Documents

  • FRM-DOSE-001 Pediatric Dose Calculation Worksheet
  • SOP-CHEMO-XXX Chemotherapy Dosing Verification
  • High-Alert Medication List
  • Pediatric Dosing Reference Guide

10. References

  • ISMP Guidelines for Standard Order Sets
  • ASHP Guidelines on Preventing Medication Errors in Hospitals
  • Pediatric dosing references (Lexicomp, Micromedex)
  • Institutional dosing guidelines
  • State Board of Pharmacy practice standards

Revision History

Rev Date Description Author
1.0 [DATE] Initial release [AUTHOR]
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