Medication Administration: Routes (Topical, IV, SQ, IM, Oral) and Techniques

Medication Administration: Routes and Techniques

Quick Answer: The veterinary technician administers medications by topical, transdermal, oral, subcutaneous (SQ), intramuscular (IM), and intravenous (IV) routes. Route choice depends on onset speed required, drug formulation, volume to deliver, patient cooperation, and clinical setting. Each route has anatomical constraints and technique traps—most notably, never aspirate an IV catheter, choose IM sites that avoid nerves, and rotate SQ injection sites to prevent tissue damage.

Route Comparison Table

Subcutaneous (SQ) Administration

Technique

1. Lift the scruff at the dorsal neck or lateral thorax to create a tent of skin.
2. Insert the needle at a 45° angle with the bevel up.
3. Aspirate gently (pull back the plunger) to confirm no blood return—SQ injections do not always yield negative pressure, but blood return indicates vessel penetration.
4. Inject slowly; volume tolerance varies—cats tolerate less per site than dogs.
5. Withdraw and apply gentle pressure if needed.

Trap callout: The scruff is the standard site but rotation matters. Repeated SQ injections at the same site (especially insulin in diabetic patients) cause lipohypertrophy and reduced absorption. Rotate sites across the dorsal neck and lateral thorax.

Volume Limits and Patient Status

• Dogs: up to ~60 mL per site for fluids; multiple sites acceptable.
• Cats: smaller volumes per site, often 10–20 mL.
• Dehydrated or vasoconstricted patients: absorption is unreliable; do not rely on SQ for emergency drug delivery.

Intramuscular (IM) Administration

IM Injection Sites by Species

IM Technique

1. Palpate the muscle belly and isolate it.
2. Insert the needle at a 90° angle to ensure intramuscular placement.
3. Aspirate by pulling back the plunger for 2–3 seconds to confirm no blood return.
4. If blood appears, withdraw and reposition with a new needle.
5. Inject slowly and withdraw smoothly.

Trap callout: Aspirate before IM injection. Hitting a vessel converts an intended IM dose into an accidental IV bolus, which can cause rapid toxicity—especially with drugs like penicillin G or sedatives. The hind limb quadriceps and gluteals are risky in both species because of the sciatic nerve; prefer the epaxial muscles.

Volume and Needle Gauge

• Volume: limit to 5 mL per site in dogs, 2–3 mL in cats.
• Needle: 22–25 G for small patients, 20–22 G for medium/large dogs.
• Needle length: short (1–1.5 inch) for cats and small dogs; longer (1.5–2.5 inch) for large dogs to ensure true IM placement rather than SQ.

Intravenous (IV) Administration

Key Principles

• IV delivery provides the fastest onset and the most reliable bioavailability (100%).
• Never aspirate an IV catheter—negative pressure traumatizes the endothelium, pulls the vessel wall against the catheter, and promotes thrombosis and occlusion. To assess patency, flush gently; resistance means stop and investigate.
• Bolus vs. CRI: boluses deliver a known dose over seconds to minutes; CRIs (continuous rate infusions) maintain steady-state drug levels (common for analgesics, antiarrhythmics).
• Flush before and after every IV medication to prevent drug-drug incompatibility within the line.

Common IV Complications

• Phlebitis: vessel inflammation, swelling, heat—remove catheter.
• Extravasation: fluid leaking into surrounding tissue—stop, aspirate back what is in the line, apply warm or cold compress per drug (some drugs like vincristine require cold).
• Thrombosis: clot occlusion—do not force flush; remove catheter.
• Air embolism: rare but life-threatening—always purge air from syringe and lines.

Oral (PO) Administration

Technique

1. Liquid: syringe into the cheek pouch, head level, slow drip to allow swallowing.
2. Tablet/capsule: place on the back of the tongue, hold mouth closed, stroke throat to encourage swallowing, or use a pill gun.
3. With food or empty per drug specifics: some drugs require food (e.g., NSAIDs to reduce GI upset); others require empty stomach (e.g., tetracyclines, which chelate with calcium).

Considerations

• Absorption is most variable of all routes due to gastric pH, emptying time, food interactions, and vomiting.
• Cooperative patient and owner education are essential for at-home oral meds.
• Pilling cats: risk of pill-induced esophagitis (especially with doxycycline and clindamycin); always follow with a small water syringe to ensure passage.

Topical and Transdermal Routes

Topical

• Eye medications (ointments, drops), ear medications, and dermatologic creams.
• Apply to clean skin/mucosa; remove prior product to avoid layering.
• For ears, gently massage the base after application to distribute.

Transdermal

• Patches (e.g., fentanyl, lidocaine) or gels (e.g., methimazole in cats).
• Application: clip a hairless area (often the ventral abdomen or inner pinna), apply to clean skin, record date and time.
• Handler safety: wear gloves; do not touch the patch with bare hands.
• Absorption is slow and variable, with peak levels hours after application.
• Persistence: drug continues to absorb for hours after patch removal—do not assume immediate cessation of effect.
• Disposal: follow controlled-substance disposal for fentanyl patches; do not throw in regular trash.

Trap callout: Transdermal fentanyl patches are a controlled substance handling trap. Used patches still contain residual drug. Log application and removal times, return used patches to the controlled-substance lockbox, and document disposal per DEA regulations.

Route Selection Decision Framework

1. Emergency or instant onset required? → IV.
2. Large volume (fluids)? → SQ if patient is stable; IV if dehydrated/critical.
3. Maintenance drug, owner-administered? → Oral.
4. Pain management over hours/days? → Transdermal or CRI.
5. Local skin/eye/ear condition? → Topical.
6. Vaccine or single-dose injectable, moderate onset acceptable? → IM (epaxial preferred).

Documentation and Safety

Every medication administration event must be recorded: drug name, dose, route, site (for injections), time, initials, and any adverse reaction observed. The veterinary technician is the last safety check before the drug reaches the patient—verify the 'Five Rights': right patient, right drug, right dose, right route, right time.