2.3 Drug Administration Routes, Preparation, and Administration

Drug Administration Routes

Drug administration routes determine how quickly and effectively a medication reaches its target in the body. The route you choose affects onset of action, bioavailability, and the patient's overall experience. This section covers the major routes, injection sites, preparation steps, delivery techniques, and safety considerations.

Drug Administration Routes

Oral (PO) is the most common route. It's convenient, non-invasive, cost-effective, and well-suited for self-administration. However, there are trade-offs:

• Onset of action is slower compared to parenteral routes.
• First-pass metabolism (where the liver partially breaks down a drug before it reaches systemic circulation) can significantly reduce bioavailability for certain medications like propranolol and lidocaine.
• Food and other drugs can alter absorption. For example, tetracyclines bind to calcium in dairy products, and bisphosphonates must be taken on an empty stomach to absorb properly.

Parenteral routes bypass the GI tract entirely, delivering medication directly into body tissues or the bloodstream. The three main parenteral routes are:

• Subcutaneous (SC): Injection into the fatty tissue just beneath the skin. Best for small volumes of non-irritating medications like insulin and heparin. Absorption is slower than IM because fatty tissue has less blood supply.
• Intramuscular (IM): Injection into muscle tissue. Absorbs faster than SC because muscle is more vascular. Accommodates larger volumes and oil-based medications such as certain vaccines and antibiotics.
• Intravenous (IV): Direct injection into a vein. Provides the fastest onset of action and allows precise dose titration. Risks include infection, phlebitis (vein inflammation), and extravasation (leakage of medication into surrounding tissue).

Topical administration applies medication directly to the skin or mucous membranes, primarily for a localized effect with minimal systemic absorption. Examples include creams, ointments, transdermal patches (such as fentanyl patches, which do deliver systemic effects through the skin), and eye drops for conditions like glaucoma.

Inhalation delivers medication directly to the lungs, producing rapid onset of action and targeting the respiratory system. Common delivery devices include:

• Metered-dose inhalers (MDIs), such as albuterol for acute bronchospasm
• Nebulizers, such as ipratropium for COPD
• Dry powder inhalers (DPIs), such as fluticasone for maintenance asthma therapy

The dosage form of a medication (tablet, solution, suspension, patch) also influences absorption rate and determines which route is appropriate.

Sites for Parenteral Therapy

Subcutaneous (SC) injection sites:

• Outer aspect of the upper arm
• Anterior abdomen (most common for insulin)
• Upper back
• Anterior thigh

Intramuscular (IM) injection sites:

• Deltoid muscle (upper arm): convenient for small-volume injections like many vaccines
• Ventrogluteal site (hip): preferred for larger volumes; thick muscle with fewer nerves and blood vessels
• Vastus lateralis (lateral thigh): often used for infants and young children
• Dorsogluteal site (buttocks): less preferred due to risk of sciatic nerve injury

Factors that guide site selection:

• Absorption rate: Muscle tissue has greater blood supply than subcutaneous tissue, so IM injections absorb faster.
• Patient comfort: Rotate injection sites to minimize tissue damage and discomfort, especially for patients receiving frequent injections (e.g., insulin-dependent diabetics).
• Medication properties: Some drugs require a specific route. Insulin is typically given SC; certain antibiotics require IM administration.
• Patient characteristics: Age, mobility, and body composition all matter. Assess whether the patient has adequate subcutaneous or muscle tissue at the intended site.

Plan for Effective Drug Administration

Safe medication administration follows a structured sequence. Use the Rights of Medication Administration (right patient, right drug, right dose, right route, right time) as your framework throughout.

1. Patient Assessment

• Review the medication order for completeness.
• Verify patient identity using at least two identifiers (name and date of birth, for example).
• Assess for allergies, contraindications, and relevant vital signs.
• Evaluate whether the medication, dose, route, and timing are appropriate for this patient right now.

2. Medication Preparation

• Perform hand hygiene and apply PPE as needed.
• Gather all necessary supplies and equipment.
• Follow aseptic technique throughout preparation.
• Double-check the medication label against the order: drug name, dose, concentration, and expiration date. Check the label three times (when you pick it up, when you prepare it, and when you return or discard the container).

3. Post-Administration Monitoring

• Assess the patient's response to the medication (is it working as expected?).
• Monitor for adverse reactions or side effects.
• Document administration details: time, dose, route, site (for injections), and any relevant observations.

4. Patient Education

• Explain the medication's purpose, expected effects, and potential side effects.
• Teach self-administration techniques when applicable (e.g., insulin injection, inhaler use).

Techniques for Medication Delivery

Oral Administration

1. Position the patient upright (at least 30 degrees) to prevent aspiration.
2. Offer water or other appropriate liquid to aid swallowing.
3. Observe the patient to confirm the medication was swallowed, especially in settings where medication diversion is a concern.

Subcutaneous and Intramuscular Injections

1. Use a new, sterile needle and syringe.

2. Clean the injection site with an alcohol swab using a circular motion from center outward. Allow it to dry.

3. For SC: pinch the skin to lift subcutaneous tissue and insert the needle at a 45- to 90-degree angle (depending on needle length and tissue amount). For IM: stretch the skin taut and insert at a 90-degree angle.

4. For IM injections, aspiration (pulling back on the plunger to check for blood return) is recommended at the dorsogluteal site but is no longer routinely required at the ventrogluteal or deltoid sites per current guidelines. Aspiration is not performed for SC injections.

5. Inject the medication slowly and steadily.

6. Remove the needle and apply gentle pressure with gauze. Do not massage an IM site if using the Z-track technique.

Intravenous Administration

1. Use strict aseptic technique when preparing and administering IV medications.
2. Assess the IV site for patency and signs of infiltration (swelling, coolness, pallor) or phlebitis (redness, warmth, tenderness along the vein).
3. Use appropriate equipment: IV pumps for rate control, proper tubing, and filters when indicated.
4. Flush the IV line with normal saline before and after medication administration to ensure full delivery and prevent drug incompatibilities.

Topical Administration

1. Wear gloves to prevent contamination and protect yourself from absorbing the medication.
2. Apply medication evenly to the affected area following package instructions.
3. Cover with a dressing if indicated.

Inhalation Administration (MDI technique)

1. Have the patient sit upright.
2. Shake the inhaler well (for MDIs).
3. Instruct the patient to exhale fully.
4. Place the mouthpiece in the mouth with lips sealed around it.
5. Coordinate pressing the canister (actuation) with a slow, deep inhalation.
6. Hold breath for approximately 10 seconds to allow medication to deposit in the airways.
7. If a second puff is prescribed, wait the recommended interval (usually 1 minute for rescue inhalers).
8. For corticosteroid inhalers, rinse the mouth with water and spit afterward to prevent oral thrush (candidiasis).

Medication Safety and Pharmacokinetics

A basic understanding of pharmacokinetics (absorption, distribution, metabolism, excretion) helps you predict how a drug will behave and why certain routes, timing, and doses are chosen. For example, knowing that a drug undergoes extensive first-pass metabolism explains why its oral dose is much higher than its IV dose.

Preventing medication errors:

• Always verify orders against the original prescription.
• Use barcode scanning and electronic medication administration records (eMARs) when available.
• Never administer a medication you didn't prepare yourself unless proper verification is in place.
• Be alert to high-alert medications (such as anticoagulants, insulin, and opioids) that carry a higher risk of harm if given incorrectly.

Drug interactions can alter a medication's efficacy or safety. Check for interactions before administering, especially when a patient is on multiple medications. Common interaction types include drugs that compete for the same metabolic enzyme (e.g., CYP450 interactions) and drugs that have additive effects (e.g., two CNS depressants).

Monitor for adverse effects after every administration. Report unexpected reactions promptly and document them in the patient's record.