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Answer route of drug administration graph
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Reading File
Here are the complete answers to all three graphs in the image:
Graph 1 - Steady State & Elimination (Top Graph)
a) What does the BLACK arrow depict?
The black arrow depicts Steady State - the point at which the rate of drug administration equals the rate of elimination, so plasma concentration stabilizes. It is attained after approximately 4-5 half-lives, and the time to reach steady state is independent of dosage.
b) How many t½ is needed for complete elimination?
4-5 half-lives (t½) are needed. After 5 half-lives, approximately 97% of the drug is eliminated from the body.
Graph 2 - Route of Drug Administration (A, B, C Curves)
The graph plots Concentration (mg/L) vs Time (hours) for three routes:
| Curve | Route | Characteristics |
|---|---|---|
| A (Blue) | Intravenous (IV) bolus | Peaks immediately at time 0 (highest initial concentration ~25 mg/L), then declines continuously - no absorption phase |
| B (Red/Dark) | Intramuscular (IM) injection | Rapid rise and peak around 2-4 hours, intermediate absorption rate |
| C (Green) | Oral (PO) administration | Slowest rise, peaks latest (~6-8 hours), lowest peak concentration due to first-pass metabolism |
b) Examples for each route:
- A - IV: Morphine IV, diazepam IV, heparin, chemotherapy drugs (e.g., cyclophosphamide)
- B - IM: Penicillin G benzathine, diclofenac IM, adrenaline (epinephrine) IM, depot antipsychotics (haloperidol decanoate)
- C - Oral: Paracetamol (acetaminophen), amoxicillin, atorvastatin, metformin
Graph 3 - Dose-Response / Therapeutic Window Graph
a) Fill in the box with the appropriate term:
The box should be labeled "Therapeutic Window" (also called Therapeutic Range or Therapeutic Index window) - the concentration range between 2-4 ng/ml where efficacy is high and adverse effects are low.
b) Comment on the graph:
- The therapeutic response curve (red/pink) rises steeply - even small increases in drug concentration produce significant therapeutic benefit in this range.
- The adverse effects curve (black) rises at higher concentrations, shifted to the right.
- The therapeutic window is the shaded region between ~2-4 ng/ml where:
- Efficacy is high (most patients respond therapeutically)
- Adverse effects are minimal (the adverse effect curve hasn't risen significantly yet)
- Below the therapeutic window: drug is sub-therapeutic (no effect)
- Above the therapeutic window: drug causes toxicity/adverse effects
- This concept is clinically important for drugs with a narrow therapeutic index (e.g., digoxin, lithium, phenytoin, aminoglycosides), requiring therapeutic drug monitoring (TDM)
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