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📚 PHAR 1322 - Parenteral Drug Delivery System

Complete SAQ & LAQ Study Guide (Section B)

Prof-Level Mastery Notes

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🎯 LEARNING OBJECTIVE 1

Define "Parenteral" and Differentiate It from the Enteral Route

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📊 TABLE 1A: Definition & Differentiation

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🧠 MEMORY TRICK #1 - "PAR = Para = PARA the GUT"

"PAR-enteral = PARk it OUTSIDE the gut" Think of it like a car parking outside the restaurant (intestine) instead of driving through the drive-thru (enteral). The drug parks outside the GI tract and goes straight to the bloodstream.

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✍️ SAQ MODEL ANSWER - LO1

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🎯 LEARNING OBJECTIVE 2

Major Advantages and Disadvantages of Parenteral Administration

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📊 TABLE 2A: Advantages vs. Disadvantages

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🧠 MEMORY TRICK #2 - The "BIRDS" vs "PAIN" Trick

• B - Bioavailability 100%
• I - Immediate onset
• R - Reversing first-pass (bypassed)
• D - Degradation avoided (no GI)
• S - Suitable for unconscious patients

• P - Pain at injection site
• I - Infection risk (sterility needed)
• N - Non-reversible once given
• S - Skilled person needed
• H - High cost
• U - Unpleasant (needle phobia)
• R - Reactions (local tissue)
• T - Trained staff required

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✍️ LAQ MODEL ANSWER - LO2

1. 100% Bioavailability (IV): Drugs administered intravenously are delivered directly into the bloodstream, completely bypassing hepatic first-pass metabolism. This is especially important for drugs like lidocaine and morphine that have extensive first-pass effect.
2. Rapid Onset: The IV route provides an immediate systemic effect, essential in emergencies (e.g., anaphylaxis - IV epinephrine).
3. Suitable for Altered Consciousness: Patients who are unconscious, vomiting, or unable to swallow can still receive medication parenterally.
4. Bypasses GI Degradation: Drugs that are acid-labile or enzymatically degraded in the GI tract (e.g., insulin, heparin) must be given parenterally as they would be destroyed if given orally.
5. Depot Formulations: IM depot injections allow sustained, controlled release over weeks to months (e.g., haloperidol decanoate for antipsychotic therapy, medroxyprogesterone for contraception).

1. Irreversibility: Unlike oral dosing, a parenteral dose cannot be retrieved. An overdose or adverse reaction may be difficult to manage.
2. Infection Risk: Breaking the skin barrier creates a portal of entry for microorganisms. Strict aseptic technique is mandatory to prevent local infection, bacteremia, and sepsis.
3. Pain: Injections are inherently painful, and can cause local tissue irritation, necrosis, or abscess formation if the drug is irritant or technique is poor.
4. Requires Skilled Personnel: Most parenteral routes (especially IV) require trained healthcare professionals, increasing cost and limiting self-administration (exception: SC insulin).
5. Risk of Phlebitis/Embolism: IV administration can cause phlebitis (vein inflammation) or air embolism if technique is improper.

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🎯 LEARNING OBJECTIVE 3

Types of Parenteral Injections: ID, SC, IM - Needle Size, Angle, Volume, Site

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📊 TABLE 3A: The Master Comparison Table (THE MOST IMPORTANT TABLE FOR EXAM)

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📊 TABLE 3B: The "45-90" Angle Quick Reference

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🧠 MEMORY TRICK #3 - "The Dart Game Trick"

• ID (5-15°): Like sliding a dart barely under wallpaper - almost horizontal, just into the skin. You see a bleb (bump) = success!
• SC (45°): Like throwing a dart at a 45° angle into a pillow (fat layer)
• IM (90°): Like throwing a dart straight into a dartboard - perpendicular, full force into muscle

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📊 TABLE 3C: The Tuberculin Skin Test (ID Application) - HIGH YIELD

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✍️ SAQ MODEL ANSWER - LO3

• Intradermal (ID): Drug is deposited into the dermis. Uses a short, fine needle (25-27G, 3/8 inch) at a 5-15° angle, delivering a tiny volume of 0.1-0.5 mL. A pale raised bleb (wheal) confirms correct placement. Used for allergy testing and TB skin test (Mantoux). Absorption is slowest due to poor dermal vascularization.
• Subcutaneous (SC): Drug is injected into the hypodermis (fatty layer). Uses a 25-27G needle (5/8-1 inch) at 45°, with volumes of 0.5-2 mL. Used for insulin, heparin, and vaccines. Absorption is slow and sustained.
• Intramuscular (IM): Drug is injected directly into muscle (deltoid, gluteus, vastus lateralis). Uses a larger needle (19-23G, 1-1.5 inches) at 90°, with volumes up to 5 mL. Faster absorption than SC due to rich muscle vascularity. Ideal for vaccines, antibiotics, and depot formulations.

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🎯 LEARNING OBJECTIVE 4

Unique Characteristics of the IV Route & Risks of Rapid Administration

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📊 TABLE 4A: Intravenous Route - Full Profile

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📊 TABLE 4B: RISKS OF RAPID IV ADMINISTRATION - HIGH YIELD ⚠️

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🧠 MEMORY TRICK #4 - "IV = INSTANT VENGEANCE"

IV gives the drug instantly - and the body's response can also be instant (vengeance)!

• C - Cardiac arrhythmia
• R - Respiratory depression
• A - Anaphylaxis
• S - Speed shock
• H - Hypotension (Red Man Syndrome)
• F - Fever/Pyrogen reaction
• A - Air embolism
• S - Site reaction (phlebitis)
• T - Thrombus

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✍️ LAQ MODEL ANSWER - LO4

1. Immediate onset: The drug enters systemic circulation instantly, with no absorption phase. This makes IV the route of choice in emergencies (e.g., anaphylaxis, status epilepticus, cardiac arrest).
2. 100% Bioavailability: No first-pass metabolism, no GI degradation - the entire dose reaches the bloodstream.
3. Large volume capacity: Unlike IM (max 5 mL) or SC (max 2 mL), IV can deliver litres of fluid via infusion (e.g., normal saline, dextrose for fluid resuscitation).
4. Controllable dosing: IV infusion rates can be titrated in real-time based on patient response.
5. Suitable for irritant drugs: Irritant drugs that would cause necrosis in tissue (e.g., vancomycin, chemotherapy agents) can be safely given IV because they are diluted by blood flow.

• "Speed Shock": Sudden systemic toxicity from any drug given too fast
• Cardiac arrhythmias/arrest: Particularly with potassium chloride - if given too rapidly, it causes fatal ventricular fibrillation
• Red Man Syndrome: Rapid vancomycin infusion causes histamine release - manifesting as flushing, erythema, and hypotension. Prevented by slowing the infusion rate to at least 60 minutes
• Respiratory depression: Fast IV opioids (morphine) or benzodiazepines reach the brainstem rapidly
• Air embolism: Air entering the IV line can cause pulmonary embolism
• Anaphylaxis: Allergic reactions to IV drugs (or their excipients) are particularly severe and fast-acting parenterally

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🎯 LEARNING OBJECTIVE 5

Identifying the Correct Parenteral Route for a Clinical Scenario

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📊 TABLE 5A: All 9 Parenteral Routes - Complete Clinical Decision Guide

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📊 TABLE 5B: Clinical Scenario Decision Framework

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🧠 MEMORY TRICK #5 - "The BODY MAP Method"

SKIN SURFACE
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   | --- ID (5-15°) --- Just under skin surface (DERMIS) = "Skin Deep"
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   | --- SC (45°) --- Fatty layer = "Belly Fat Level"  
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   | --- IM (90°) --- Muscle = "Muscle Punch Level"
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   | --- IV --- Vein = "Blue Line Level"
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   | --- IO --- Bone marrow = "Deepest Emergency Level"

• Joint pain? → Intra-articular
• Back/spine? → Intra-thecal
• Belly/abdomen cancer? → Intra-peritoneal
• Organ-specific cancer? → Intra-arterial
• No vein access in emergency? → Intra-osseous

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🧠 MASTER MEMORY SYSTEM - "The PHAR INJECTION CHANT"

"ID is 15, SC is 45, IM is 90 - that's how needles FLY!" "ID is tiny 0.1 to 0.5, SC is small 0.5 to 2, IM is BIG up to FIVE!"

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⚡ RAPID-FIRE EXAM KEYWORDS - ALL LEARNING OBJECTIVES

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🏆 EXAM STRATEGY SUMMARY

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What You Got:

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3 Things to Memorize First (Highest Exam Yield):

1. The Angle Rule: ID = 5-15° | SC = 45° | IM = 90°
2. The Volume Rule: ID = 0.1-0.5 mL | SC = 0.5-2 mL | IM = up to 5 mL
3. IV Risks Chant: "CRASH FAST" (Cardiac, Respiratory, Anaphylaxis, Speed shock, Hypotension, Fever, Air embolism, Site reaction, Thrombus)