Domain 4.2General Patient Care

Pharmacology Immunizations Administration

Last updated June 16, 2026

Overview

This guide unifies medication administration and immunizations. As a Medical Assistant, you must safely administer medications, calculate dosages, and manage vaccine schedules. Immunization is simply a specific application of medication administration; therefore, the safety rules, injection angles, and documentation requirements apply universally.

1. Foundational Principles: Safety First

The "Rights" of Administration

Always verify the following before administering any drug or vaccine:

  1. Right Patient (Two identifiers)
  2. Right Medication (Check label 3 times)
  3. Right Dose (Verify calculation)
  4. Right Route (IM, SQ, PO)
  5. Right Time
  6. Right Documentation (Immediately after—include site for injections)

The Three Checks

Perform these checks every time:

  1. When removing medication from storage.
  2. When preparing/drawing up the medication.
  3. At the patient's side before administration.

2. Routes of Administration

Nonparenteral Routes

  • Oral (PO): Swallowed. NEVER crush enteric-coated or extended-release (XR/ER) tablets.
    • Liquid Medications: To measure accurately, pour the medication into a cup placed on a flat surface. View the cup at eye level to read the meniscus (the lowest point of the liquid curve).
  • Sublingual (SL): Under the tongue.
  • Buccal: Between cheek and gum.
  • Transdermal: Patches. Rotate sites to prevent irritation. Never apply heat over a patch.
  • Ophthalmic (Eye): Drops into the conjunctival sac. Do not touch the dropper to the eye.
  • Otic (Ear):
    • Warmth: Always warm ear drops to body temperature (e.g., roll bottle in hands) before administration. Cold drops can cause vertigo (dizziness) or discomfort.
    • Adults: Pull pinna UP and BACK.
    • Children (<3): Pull pinna DOWN and BACK.

Parenteral Routes (Injections)

Needle Gauge Rule: Higher number = Smaller needle (e.g., 27G is smaller than 18G).

Type Angle Target Common Gauge Primary Sites
Intradermal (ID) 10-15° Dermis 27-29 G Forearm (TB/PPD test, Allergy test)
Subcutaneous (SQ) 45° or 90° Fat 25-27 G Abdomen, Back of Arm (Insulin, MMR, Varicella)
Intramuscular (IM) 90° Muscle 22-25 G Deltoid, Vastus Lateralis, Ventrogluteal

IM Site Specifics

  • Deltoid: 2-3 finger widths below acromion process. Max 1 mL.
  • Vastus Lateralis: Outer thigh. Preferred site for infants/children < 2 years. Also used for adults requiring large volumes (up to 3-5 mL) if the ventrogluteal site is not accessible.
  • Ventrogluteal: Hip. Safest for adults (no major nerves). Good for large volumes.
  • Z-Track Method: Pull skin taut before IM injection to lock irritating meds (like Iron) in muscle.

3. Immunizations

Schedules & Milestones (High-Yield)

  • Hepatitis B: First dose at Birth ("B is for Birth").
  • 11-12 Years: Tdap, HPV, Meningococcal ("Middle School Shots").
  • Adults: Flu (Annually), Td (Every 10 years).
  • Pregnancy/Deep Wounds: Tdap is priority.

Patient Safety & Contraindications

  • Anaphylaxis: Universal contraindication.
  • Guillain-Barré Syndrome (GBS): Major contraindication for Flu Vaccine.
  • Live Vaccines (MMR, Varicella): Avoid in immunocompromised or pregnant patients.

Legal Requirements

  • Vaccine Information Statement (VIS): Must be given BEFORE every dose. Document the edition date and date provided.
  • Informed Consent: Patient education must always cover both the Benefits (protection from disease) and the Risks (potential side effects) of the vaccine.
  • Lot Number: The most critical detail for tracking vaccine batches in case of a recall.

4. Dosage Calculations

Basic Formula: (Dose Ordered / Dose on Hand) x Quantity = Amount to Give

Example:

  • Order: 500 mg
  • Supply: 250 mg per 5 mL
  • Calculation: (500 / 250) = 2.
  • 2 x 5 mL = 10 mL.

Metric Conversions (High-Yield)

  • mcg to mg: 1000 micrograms (mcg) = 1 milligram (mg).
  • Rule: To convert mcg to mg, divide by 1000 (move decimal 3 places to the LEFT).
    • Example: 250 mcg = 0.25 mg.
  • mg to mcg: Multiply by 1000 (move decimal 3 places to the RIGHT).

Weight-Based (Pediatrics):

  1. Convert lbs to kg (lbs / 2.2).
  2. Multiply kg x mg/kg prescribed.

5. Storage and Documentation

  • Documentation: Always chart the SITE of injection. If you didn't chart it, you didn't do it.
  • Vaccine Inventory Log: Federal guidelines require recording specific data for every vaccine dose administered and in stock.
    • Required Data: Manufacturer, Lot Number, and Expiration Date.
  • Vaccine Storage:
    • Monitoring: Place a thermometer in BOTH the refrigerator and the freezer. Check temperatures twice daily.
    • Store in the center of the fridge, never the door.
    • FIFO: First-In, First-Out (use older stock first).

6. Final Key Takeaways

  • Angles: IM=90°, SQ=45°, ID=10-15°.
  • Infant IM Site: Vastus Lateralis.
  • Recall Safety: Record the Lot Number and Manufacturer.
  • Storage: Monitor both fridge and freezer temps.
  • Education: Never crush XR meds. Rotate patches. Discuss Risks/Benefits.
  • Conversions: 1 kg = 2.2 lbs. 1 mg = 1000 mcg.
  • Insulin: Uses a U-100 syringe (measured in units).