Medication Administration & Dosage Calculations

Posted on by Soumya Ranjan Parida
Medication Administration and Dosage Calculations – Nursing Study Notes

Medication Administration & Dosage Calculations

Comprehensive Nursing Study Notes

Evidence-Based Practice Guidelines

Medication Administration and Dosage Calculations

Table of Contents

Part I: Systems of Measurement

Metric System

The metric system is the most commonly used measurement system in healthcare worldwide. It’s based on units of ten, making conversions straightforward and reducing calculation errors.

Length

  • • Meter (m) – base unit
  • • Centimeter (cm) = 0.01 m
  • • Millimeter (mm) = 0.001 m
  • • Kilometer (km) = 1000 m

Weight

  • • Gram (g) – base unit
  • • Milligram (mg) = 0.001 g
  • • Microgram (mcg) = 0.000001 g
  • • Kilogram (kg) = 1000 g

Volume

  • • Liter (L) – base unit
  • • Milliliter (mL) = 0.001 L
  • • Cubic centimeter (cc) = 1 mL
  • • Microliter (μL) = 0.000001 L

Mnemonic for Metric Prefixes

“King Henry Died By Drinking Chocolate Milk”

Kilo → Hecto → Deka → Base → Deci → Centi → Milli

Imperial System

The imperial system is primarily used in the United States. While less common in healthcare globally, nurses must be familiar with these measurements for patient care and documentation.

Length

  • • 12 inches = 1 foot
  • • 3 feet = 1 yard
  • • 5,280 feet = 1 mile

Weight

  • • 16 ounces = 1 pound
  • • 2,000 pounds = 1 ton

Household System

The household system uses common kitchen measurements. It’s important for patient education and home medication administration.

Volume Equivalents

  • • 1 teaspoon (tsp) = 5 mL
  • • 1 tablespoon (tbsp) = 15 mL
  • • 1 fluid ounce (fl oz) = 30 mL
  • • 1 cup = 240 mL
  • • 1 pint = 480 mL
  • • 1 quart = 960 mL
  • • 1 gallon = 3,840 mL

Unit Conversions

Accurate unit conversions are critical for patient safety. Always double-check your calculations and use the appropriate conversion factors.

Common Weight Conversions

  • • 1 kg = 2.2 lbs
  • • 1 lb = 0.45 kg
  • • 1 oz = 28.35 g
  • • 1 grain = 65 mg

Common Volume Conversions

  • • 1 L = 1,000 mL
  • • 1 mL = 1 cc
  • • 1 fl oz = 30 mL
  • • 1 tsp = 5 mL

Part II: Medication Dose Calculations

Basic Dosage Calculation Formulas

Universal Dosage Formula

Desired Dose ÷ Dose on Hand × Quantity = Amount to Give

Where:
  • • Desired Dose = What the physician ordered
  • • Dose on Hand = Strength of medication available
  • • Quantity = Amount of medication that contains the dose on hand
  • • Amount to Give = How much to administer
Example:

Order: 500 mg of medication
Available: 250 mg tablets
Calculation: 500 ÷ 250 × 1 = 2 tablets

Ratio and Proportion Method

Known : Unknown = Available : Desired

Example: 250 mg : 1 tablet = 500 mg : X tablets

Dimensional Analysis

Multiply by conversion factors to cancel units

Example: 500 mg × (1 tablet/250 mg) = 2 tablets

Pediatric Dosing Calculations

Pediatric dosing requires special consideration due to physiological differences in children. Most pediatric doses are calculated based on body weight or body surface area.

Weight-Based Dosing

Formula: mg/kg × weight (kg) = total dose

Example: 10 mg/kg for 20 kg child = 200 mg total dose

Body Surface Area (BSA)

BSA (m²) = √(height × weight) ÷ 3600

Then: mg/m² × BSA = total dose

Pediatric Safety Considerations

  • • Always verify weight in kg for calculations
  • • Check dose against safe dosing ranges
  • • Consider age-appropriate formulations
  • • Use appropriate measuring devices

IV Flow Rate Calculations

IV Flow Rate Formulas

Drops per Minute (gtt/min)

Volume × Drop Factor ÷ Time (min) = gtt/min

Milliliters per Hour (mL/hr)

Total Volume ÷ Time (hours) = mL/hr

Common Drop Factors

Macrodrip Sets:

  • • 10 gtt/mL
  • • 15 gtt/mL
  • • 20 gtt/mL

Microdrip Sets:

  • • 60 gtt/mL

Blood Sets:

  • • 10 gtt/mL
  • • 15 gtt/mL

Concentration Calculations

Percentage Concentrations

  • • Weight/Volume (w/v): grams per 100 mL
  • • Volume/Volume (v/v): mL per 100 mL
  • • Weight/Weight (w/w): grams per 100 g

Parts per Million (ppm)

1 ppm = 1 mg/L = 1 mcg/mL

Used for very dilute solutions

Part III: Principles of Medication Administration

The Ten Rights of Medication Administration

The Ten Rights provide a systematic approach to safe medication administration. These rights serve as checkpoints to prevent medication errors and ensure patient safety.

1. Right Patient

  • • Use two patient identifiers
  • • Check patient ID bracelet
  • • Ask patient to state name and DOB
  • • Verify with medical record

2. Right Drug

  • • Compare order with medication label
  • • Check generic and brand names
  • • Verify drug classification
  • • Look for similar drug names

3. Right Dose

  • • Calculate dose accurately
  • • Double-check calculations
  • • Verify with another nurse if needed
  • • Check dose against normal ranges

4. Right Route

  • • Verify route in medication order
  • • Ensure patient can take via ordered route
  • • Check for route contraindications
  • • Use appropriate administration technique

5. Right Time

  • • Administer within 30 minutes of ordered time
  • • Consider drug half-life
  • • Check for food interactions
  • • Maintain consistent timing

6. Right Documentation

  • • Document immediately after administration
  • • Include all required information
  • • Note patient response
  • • Record any complications

7. Right Reason

  • • Understand indication for medication
  • • Verify appropriateness for patient
  • • Check for contraindications
  • • Assess patient’s condition

8. Right Response

  • • Monitor for therapeutic effects
  • • Watch for adverse reactions
  • • Assess patient’s response
  • • Follow up as needed

9. Right to Know

  • • Educate patient about medication
  • • Explain purpose and effects
  • • Discuss potential side effects
  • • Answer patient questions

10. Right to Refuse

  • • Respect patient autonomy
  • • Document refusal
  • • Notify physician
  • • Explore reasons for refusal

Mnemonic for Ten Rights

“Pretty Doctors Don’t Really Trust Dangerous Remedies, Requiring Knowing Rejection”

Patient → Drug → Dose → Route → Time → Documentation → Reason → Response → Right to Know → Right to Refuse

Routes of Administration

Enteral Routes

  • • Oral (PO) – by mouth
  • • Sublingual (SL) – under tongue
  • • Buccal – between cheek and gum
  • • Nasogastric (NG) – through nose to stomach
  • • Gastrostomy (G-tube) – directly into stomach
  • • Jejunostomy (J-tube) – directly into jejunum

Parenteral Routes

  • • Intravenous (IV) – into vein
  • • Intramuscular (IM) – into muscle
  • • Subcutaneous (SC/SQ) – under skin
  • • Intradermal (ID) – into dermis
  • • Intrathecal (IT) – into spinal canal
  • • Intraosseous (IO) – into bone

Topical Routes

  • • Transdermal – through skin
  • • Ophthalmic – into eye
  • • Otic – into ear
  • • Nasal – into nose
  • • Vaginal – into vagina
  • • Rectal – into rectum

Inhalation Routes

  • • Nebulizer – liquid to mist
  • • Metered-dose inhaler (MDI)
  • • Dry powder inhaler (DPI)
  • • Endotracheal – through ET tube

Documentation Requirements

Essential Documentation Elements

  • • Date and time of administration
  • • Medication name and dose
  • • Route of administration
  • • Site of administration (if applicable)
  • • Patient response
  • • Nurse signature and credentials
  • • Any adverse reactions
  • • Reason for PRN medications
  • • Patient education provided
  • • Medication refused (if applicable)

Part IV: Medication Errors and Prevention

Common Medication Errors

Calculation Errors

  • • Decimal point misplacement
  • • Unit conversion mistakes
  • • Mathematical calculation errors
  • • Misinterpretation of dosing formulas

Communication Errors

  • • Verbal orders misunderstood
  • • Illegible handwriting
  • • Abbreviation misinterpretation
  • • Incomplete medication orders

System Errors

  • • Pharmacy dispensing errors
  • • Computer system failures
  • • Medication storage issues
  • • Equipment malfunctions

Human Factors

  • • Fatigue and stress
  • • Interruptions during medication preparation
  • • Inadequate knowledge
  • • Overconfidence or rushing

High-Alert Medications

These medications require special precautions due to their potential for serious harm:

  • • Insulin
  • • Heparin
  • • Warfarin
  • • Digoxin
  • • Chemotherapy agents
  • • Opioids
  • • Concentrated electrolytes
  • • Neuromuscular blocking agents
  • • Adrenergic agonists
  • • Adrenergic antagonists
  • • Anesthetic agents
  • • Antiarrhythmics

Error Prevention Strategies

Individual Strategies

  • • Follow the Ten Rights consistently
  • • Double-check calculations
  • • Use independent double-checking
  • • Minimize interruptions
  • • Stay current with knowledge
  • • Ask questions when uncertain

System-Based Strategies

  • • Computerized provider order entry
  • • Barcode medication administration
  • • Smart infusion pumps
  • • Automated dispensing systems
  • • Medication reconciliation
  • • Standardized protocols

Safety Practices

  • • Never bypass safety systems
  • • Report near misses and errors
  • • Participate in safety initiatives
  • • Use tall man lettering for look-alike drugs
  • • Implement read-back verification
  • • Use standardized units and abbreviations
  • • Maintain medication knowledge
  • • Practice open communication

Error Reporting and Response

Immediate Actions After Error Discovery

  1. 1. Ensure patient safety
  2. 2. Assess patient condition
  3. 3. Notify physician immediately
  4. 4. Follow institutional protocol
  1. 5. Document the error
  2. 6. Report to appropriate personnel
  3. 7. Monitor patient response
  4. 8. Learn from the experience

Reporting Culture

  • • Focus on system improvement, not blame
  • • Encourage reporting of near misses
  • • Use just culture principles
  • • Share lessons learned
  • • Implement corrective actions

Nursing Implications and Best Practices

Professional Responsibilities

  • • Maintain competency in medication administration
  • • Understand pharmacokinetics and pharmacodynamics
  • • Recognize drug interactions and contraindications
  • • Advocate for patient safety
  • • Participate in quality improvement initiatives

Legal and Ethical Considerations

  • • Follow scope of practice guidelines
  • • Maintain accurate documentation
  • • Respect patient autonomy
  • • Protect patient confidentiality
  • • Report unsafe practices

SAFETY Mnemonic for Medication Administration

  • S – Stop and think before administering
  • A – Assess patient condition
  • F – Follow protocols and procedures
  • E – Evaluate medication order
  • T – Take time to double-check
  • Y – Yield to safety concerns

Conclusion

Medication administration is one of the most critical responsibilities in nursing practice. The principles and practices outlined in these notes provide a comprehensive foundation for safe and effective medication administration. Remember that medication errors can have serious consequences, but they are largely preventable through diligent application of safety principles, continuous learning, and adherence to best practices.

As healthcare continues to evolve, nurses must stay current with new technologies, medications, and safety practices. The Ten Rights of Medication Administration serve as timeless principles that should guide every medication-related decision. By combining these principles with strong calculation skills, system-based safety measures, and a commitment to continuous improvement, nurses can significantly reduce medication errors and improve patient outcomes.

Remember: When in doubt, don’t guess. Ask questions, seek clarification, and never compromise on patient safety. Every medication administration is an opportunity to demonstrate professional competence and commitment to patient care.

Quick Reference Card

Common Conversions

  • • 1 kg = 2.2 lbs
  • • 1 tsp = 5 mL
  • • 1 tbsp = 15 mL
  • • 1 oz = 30 mL
  • • 1 g = 1000 mg

Dosage Formula

Desired ÷ On Hand × Quantity = Amount

IV Flow Rate

Volume × Drop Factor ÷ Time = gtt/min

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