# 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 |

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## 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

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## Revision History

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