All viva related questions for iv route of drug administration pharmacology 2nd year mbba
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Viva Questions: Intravenous (IV) Route of Drug Administration
Pharmacology - 2nd Year MBBS
1. What is the intravenous (IV) route of drug administration?
The IV route involves injecting a drug directly into a vein, delivering it straight into the systemic circulation. It is the most common parenteral route and bypasses all absorption barriers.
- Lippincott Pharmacology, p. 25
2. What are the types of IV administration?
- IV bolus (push): The full drug dose is delivered rapidly into the bloodstream almost immediately. Results in high peak plasma concentrations.
- IV infusion: Drug is administered slowly over a longer period, producing lower peak plasma concentrations but a sustained circulating drug level.
3. What are the advantages of the IV route?
| Advantage | Explanation |
|---|---|
| Rapid onset | Drug enters systemic circulation directly - no absorption phase |
| 100% bioavailability | No first-pass metabolism; the entire dose reaches circulation |
| Precise control | Exact dosing; rate can be adjusted |
| Useful when oral route fails | Unconscious patients, drugs destroyed in GI tract (e.g., insulin, heparin) |
| Large volumes possible | Fluids and electrolytes can be given in large amounts |
| Immediate reversal | Dose can be titrated in real time |
- Lippincott Pharmacology, p. 25; Goodman & Gilman, p. 1440
4. What are the disadvantages/adverse effects of the IV route?
| Disadvantage | Explanation |
|---|---|
| Irreversible | Once injected, the drug cannot be recalled - any adverse reaction is immediate |
| Pain and fear | Needles cause discomfort |
| Infection risk | Septicemia, phlebitis if aseptic technique is not followed |
| Thrombophlebitis | Inflammation of the vein wall from irritant drugs or repeated cannulation |
| Air embolism | Air accidentally entering the IV line can be fatal |
| Extravasation | Drug leaking into surrounding tissue causes necrosis (e.g., chemotherapy agents) |
| Overdose risk | Rapid delivery means overdose effects occur almost immediately |
| Requires trained personnel | Cannot self-administer |
5. What is bioavailability and why is it 100% for IV drugs?
Bioavailability is the fraction of an administered dose that reaches the systemic circulation unchanged. For IV drugs, bioavailability is 100% because the drug is injected directly into the bloodstream, bypassing the GI tract and liver - so no first-pass metabolism occurs.
- Lippincott Pharmacology, p. 41
6. What is first-pass metabolism? How does IV route avoid it?
First-pass (presystemic) metabolism is the biotransformation of a drug in the gut wall or liver before it enters systemic circulation. Drugs absorbed orally enter the portal circulation and pass through the liver first.
IV drugs bypass the portal circulation entirely, so they are NOT subject to first-pass metabolism. This is why drugs like nitroglycerin (>90% cleared by first-pass orally) are given IV, sublingually, or transdermally.
- Lippincott Pharmacology, p. 41
7. Name drugs that MUST be given intravenously (cannot be given orally). Why?
| Drug | Reason |
|---|---|
| Heparin | Poorly absorbed from GI tract |
| Insulin | Destroyed by GI tract proteases |
| Rocuronium (neuromuscular blocker) | Not absorbed orally |
| Gentamicin (aminoglycosides) | Poorly absorbed orally |
| Dopamine, norepinephrine | Extensive first-pass metabolism |
8. What happens pharmacokinetically after an IV bolus dose?
After IV bolus:
- Distribution phase - drug rapidly leaves the bloodstream and enters tissues. Plasma concentration falls quickly.
- Elimination phase - drug is metabolized/excreted at a slower rate; plasma concentration falls more gradually.
The initial steep fall in plasma concentration represents distribution, not elimination. This two-phase decline is described by a two-compartment model.
- Lippincott Pharmacology, p. 44; Katzung, block 1
9. What is the difference between IV bolus and IV infusion (pharmacokinetically)?
| Parameter | IV Bolus | IV Infusion |
|---|---|---|
| Peak plasma concentration | Very high, immediate | Lower, gradual |
| Onset | Fastest | Slightly slower |
| Duration | Shorter | Longer/sustained |
| Risk of toxicity | Higher | Lower (titratable) |
| Use | Emergency, anesthesia induction | Maintenance, antibiotics |
10. What is meant by "steady-state concentration" in IV infusion?
When a drug is infused at a constant rate, the plasma concentration rises and eventually plateaus at a steady state where the rate of infusion equals the rate of elimination. This takes approximately 4-5 half-lives to achieve.
11. What are the sites used for IV administration?
- Peripheral veins: Antecubital fossa (median cubital vein), dorsum of hand, cephalic, basilic veins - used for routine IV
- Central veins: Subclavian, internal jugular, femoral veins - used for vasopressors, TPN, CVP monitoring
- Scalp veins - used in infants
During CPR, peripheral IV is standard but central vein IV gives the most rapid and highest drug levels.
- Barash Clinical Anesthesia, p. 1878
12. What is the preferred IV route during CPR and why?
The preferred route is intravenous. Central venous administration produces the most rapid and highest drug levels, but peripheral IV is used first in CPR to avoid interrupting compressions. Drugs should be followed by a 20 mL saline flush and limb elevation.
If IV access is unavailable, the intraosseous (IO) route is used as an alternative.
- Barash Clinical Anesthesia, p. 1878
13. What precautions must be taken when giving IV drugs?
- Strict aseptic technique
- Check compatibility before mixing drugs in the same line
- Ensure correct dilution and rate of administration
- Watch for signs of extravasation (redness, swelling at site)
- Avoid air bubbles in the line (risk of air embolism)
- Check for correct vein placement before injection
- Monitor for allergic/anaphylactic reactions
14. Compare IV route with IM and SC routes:
| Feature | IV | IM | SC |
|---|---|---|---|
| Onset | Fastest | Moderate | Slow |
| Bioavailability | 100% | ~75-90% | ~75-90% |
| First-pass metabolism | Absent | Absent | Absent |
| Pain | Moderate | Moderate | Minimal |
| Volume | Large (up to 1L+) | Up to 5 mL | Up to 1-2 mL |
| Depot preparation | No | Yes | Yes |
| Hemolysis/thrombosis risk | Yes | No | Minimal |
- Lippincott Pharmacology, p. 26
15. What is thrombophlebitis? How is it caused by IV drugs?
Thrombophlebitis is inflammation of a vein with clot formation. It is caused by:
- Irritant or hypertonic drugs (e.g., erythromycin, certain chemotherapy agents, diazepam in propylene glycol)
- Repeated cannulation at the same site
- Infection from poor aseptic technique
Presents as pain, redness, swelling along the vein.
16. What is extravasation and which drugs are dangerous?
Extravasation is the leakage of IV fluid/drug into surrounding tissue. It is especially dangerous with vesicant drugs that cause tissue necrosis:
- Chemotherapy agents: doxorubicin, vincristine
- Vasopressors: norepinephrine
- Hypertonic solutions: calcium chloride, potassium chloride
Management: Stop infusion immediately, aspirate, apply antidote (if available), hyaluronidase, warm/cold compresses depending on the agent.
17. Why can some drugs NOT be given IV?
- Oil-based preparations - can cause pulmonary embolism (e.g., depot preparations)
- Drugs causing severe hemolysis - osmotically active, incompatible with blood
- Drugs that precipitate in blood - e.g., phenytoin (must use phosphenytoin IV or slow rate)
- Drugs that cause anaphylaxis - though some are given IV with premedication
18. What is volume of distribution (Vd) and how does IV dosing help calculate it?
Volume of distribution (Vd) = Amount of drug in body / Plasma drug concentration
For IV dosing, since the entire dose is in the body at time zero (100% bioavailability), Vd can be calculated precisely using the initial plasma concentration after an IV bolus. This is why IV bolus is used as the reference standard for pharmacokinetic calculations.
19. What is the significance of IV route in therapeutics for specific conditions?
| Condition | Why IV is preferred |
|---|---|
| Status epilepticus | Rapid onset needed; IV lorazepam/phenytoin |
| Anaphylaxis | IV epinephrine/adrenaline for severe cases |
| Septic shock | IV antibiotics + fluids; rapid distribution needed |
| Acute MI / thrombolysis | IV streptokinase/tPA - immediate action needed |
| General anesthesia induction | IV propofol - precise, rapid control |
| Hypertensive crisis | IV labetalol/sodium nitroprusside - titratable |
20. Quick Memory: Mnemonics for IV route
Advantages of IV - "FRIC-P"
- Fastest onset
- Reliable 100% bioavailability
- Independent of GI absorption
- Controlled dosing (can titrate)
- Preferred in emergencies
Disadvantages of IV - "ATIPE"
- Air embolism
- Thrombophlebitis
- Irreversible (cannot withdraw)
- Pain / infection
- Extravasation
Sources: Lippincott Illustrated Reviews Pharmacology; Goodman & Gilman's The Pharmacological Basis of Therapeutics; Barash Clinical Anesthesia, 9e; Katzung's Basic and Clinical Pharmacology, 16e
Method of iv routes
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Technique? Of iv route called
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I have all the information needed. Here is the complete answer on techniques of IV route:
Techniques of IV Route of Drug Administration
The IV route has 4 main techniques (methods of delivery):
1. IV Bolus (IV Push)
- A single, concentrated dose is injected rapidly into a vein over a few seconds to minutes
- The entire dose reaches systemic circulation almost immediately
- Produces very high peak plasma concentrations rapidly
- Used when an immediate effect is needed
Examples: IV adrenaline in anaphylaxis, IV diazepam in status epilepticus, IV atropine in bradycardia
Risk: High chance of toxicity if injected too fast (e.g., IV calcium gluconate must be given slowly to avoid cardiac arrest)
2. IV Slow Injection (Slow IV Push)
- Same as bolus but given slowly over 5-10 minutes
- Reduces the risk of adverse effects from rapid drug concentration peaks
- Used for drugs that cause reactions if given too fast
Examples: IV phenytoin (must be given at ≤50 mg/min), IV morphine, IV ampicillin
3. IV Infusion (IV Drip)
Drug is diluted in a large volume of fluid (normal saline, dextrose) and administered over a prolonged period via a drip set.
Types of IV Infusion:
| Type | Description | Example |
|---|---|---|
| Continuous infusion | Drug runs at a constant rate over hours/days | Dopamine, oxytocin, insulin, heparin |
| Intermittent infusion | Drug given over 30-60 min at intervals (e.g., every 8 hours) | IV antibiotics (amoxicillin, vancomycin) |
| IV Piggyback (IVPB) | Small bag of drug connected to a running main IV line; runs concurrently | Common for antibiotic doses in wards |
Produces: Lower peak plasma concentration, prolonged effect, better safety profile
4. IV Infusion with Loading Dose
- A loading dose (bolus) is given first to rapidly achieve therapeutic plasma concentration
- Followed by a maintenance infusion to keep concentration at steady state
Examples:
- Amiodarone: loading 300 mg IV bolus → maintenance infusion
- Lidocaine: loading dose → continuous infusion
- Heparin: loading bolus → continuous infusion
5. Patient-Controlled Analgesia (PCA) - Special Technique
A specialized IV technique where the patient self-administers preset bolus doses by pressing a button on a computerized pump. Safety features include:
- Lockout time between doses
- Maximum dose per hour limit
- Optional low background infusion
Common drugs: IV morphine, fentanyl, tramadol (postoperative pain)
- Miller's Anesthesia, 10e, p. 3146
6. Target-Controlled Infusion (TCI) - Advanced Technique
A computer-controlled infusion pump that automatically calculates and adjusts the infusion rate to achieve a target plasma or effect-site drug concentration, based on the patient's pharmacokinetic parameters (age, weight, sex).
Used mainly in anesthesia for propofol, remifentanil.
- Miller's Anesthesia, 10e
Summary Table
| Technique | Speed | Peak Conc. | Control | Use |
|---|---|---|---|---|
| IV Bolus | Seconds | Very high | Low | Emergencies |
| Slow IV Push | 5-10 min | High | Moderate | Irritant drugs |
| Continuous Infusion | Hours-days | Low, steady | High | ICU drugs, maintenance |
| Intermittent Infusion | 30-60 min | Moderate | Moderate | Antibiotics |
| Loading + Maintenance | Bolus then infusion | Therapeutic immediately | Best | Antiarrhythmics, anticoagulants |
| PCA | Patient-triggered | Controlled | Patient | Post-op pain |
| TCI | Computer-driven | Target set | Highest | Anesthesia |
Key Viva Points
Q: What is the most common technique for emergency drugs? A: IV bolus - fastest onset, full dose immediately in circulation.
Q: Why give a loading dose before infusion? A: Without a loading dose, continuous infusion alone takes 4-5 half-lives to reach steady state. Loading dose achieves therapeutic level immediately.
Q: What is the risk of IV bolus vs infusion? A: Bolus = high risk of toxicity (high peak). Infusion = safer, titratable, sustained levels.
Q: Name a drug that MUST be given as slow IV, not fast bolus. A: Phenytoin (causes cardiac arrhythmia if given fast), Vancomycin (causes "Red Man Syndrome" if given too fast), Potassium chloride (fatal if given as bolus).
- Lippincott Pharmacology; Miller's Anesthesia, 10e; Barash Clinical Anesthesia, 9e
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