AIM Step 10
3rd Year MBBS
Foundation Module
3rd Year MBBS
Foundation Module
Student Memory Support
Foundations of Pharmacology, Drug Sources, Routes, Absorption and Bioavailability
High-yield memory reinforcement and last-minute KMU revision.
1. High-Yield Flashcards
Tap each question to reveal the answer.
What is the difference between pharmacokinetics and pharmacodynamics?
Pharmacokinetics = what the body does to the drug; pharmacodynamics = what the drug does to the body.
What is a pro-drug?
A drug given in an inactive or less active form that is converted in the body into an active compound.
What is a prototype drug?
A representative drug used to illustrate the main properties of a drug class.
What does pharmacogenetics study?
How inherited genetic differences influence an individual’s response to drugs.
What does pharmacogenomics study?
The broader relationship between genomic variation and drug response.
What is an active principle of a crude drug?
The chemically active constituent responsible for the medicinal effect of the crude drug.
Which route provides complete systemic availability without an absorption step?
Intravenous administration.
Why is the sublingual route useful when rapid action is required?
It provides rapid mucosal absorption and largely avoids initial hepatic first-pass metabolism.
How does topical administration differ from transdermal administration?
Topical administration mainly produces a local effect; transdermal administration delivers drug across skin for systemic action.
Which membrane transport process is most important for many lipid-soluble drugs?
Simple diffusion down the concentration gradient.
Which transport mechanism uses a carrier but no metabolic energy?
Facilitated diffusion.
Which transport mechanism can move a substance against its concentration gradient?
Active transport, which uses a carrier and energy.
Which form of a weak acid or weak base generally crosses lipid membranes more readily?
The non-ionized, more lipid-soluble form.
What is ion trapping?
Accumulation of a drug in a compartment after it becomes ionized and can no longer cross the membrane readily.
What does bioavailability describe?
The fraction of an administered dose of unchanged drug that reaches the systemic circulation.
What does the area under the concentration-time curve represent?
Overall systemic exposure to the drug.
What is hepatic first-pass effect?
Metabolism of absorbed drug in the intestinal wall or liver before it reaches systemic circulation.
What is enterohepatic circulation?
Biliary excretion of a drug or metabolite followed by intestinal reabsorption and return through portal circulation.
2. Mnemonics
Mnemonic Title:
Major Pharmacokinetic Processes
Mnemonic Word:
ADME
Meaning:
Absorption → Distribution → Metabolism → Excretion.
Mnemonic Title:
Major Enteral Routes
Mnemonic Word:
OSR
Meaning:
Oral → Sublingual → Rectal.
Mnemonic Title:
Factors Promoting Absorption
Mnemonic Word:
LBSCD
Meaning:
Lipid solubility → Blood flow → Surface area → Concentration gradient → Dissolution.
3. Memory Tables
Topical vs Transdermal Administration
| Feature | Topical | Transdermal |
|---|---|---|
| Main purpose | Local effect | Systemic effect |
| Drug destination | Site of application | Systemic circulation |
| First-pass exposure | Not the main concern | Avoids initial hepatic first-pass |
Simple Diffusion vs Facilitated Diffusion vs Active Transport
| Feature | Simple Diffusion | Facilitated Diffusion | Active Transport |
|---|---|---|---|
| Carrier | No | Yes | Yes |
| Energy | No | No | Required |
| Gradient | Down | Down | Can move against |
| Saturable | No carrier saturation | Yes | Yes |
4. Rapid Revision Points — Last-Minute Revision
Must Remember:
- Pharmacokinetics includes absorption, distribution, metabolism and excretion.
- Pharmacodynamics describes drug actions and effects on the body.
- Genetic engineering can produce therapeutic proteins such as recombinant human insulin.
- Intravenous administration provides complete systemic availability without an absorption phase.
- Sublingual administration gives rapid absorption and reduces initial hepatic first-pass exposure.
- In shock, intramuscular and subcutaneous absorption may fall because local blood flow is reduced.
- Non-ionized drug molecules generally cross lipid membranes more readily.
- A larger absorptive surface and greater blood flow favor drug absorption.
- AUC reflects overall systemic exposure to a drug.
- First-pass metabolism can reduce oral bioavailability despite adequate gastrointestinal absorption.
- Enterohepatic recycling can prolong drug persistence by allowing intestinal reabsorption after biliary excretion.
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KMU Exam Trap: Pharmaceutical equivalence does not automatically mean bioequivalence. Bioequivalence additionally requires comparable rate and extent of systemic availability.
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5. Clinical Memory Hooks
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Acute ischemic chest discomfort requiring rapid drug action
→
Sublingual route
→
rapid absorption with reduced first-pass metabolism.
→
Sublingual route
→
rapid absorption with reduced first-pass metabolism.
Profound circulatory shock after intramuscular injection
→
reduced muscle perfusion
→
delayed drug absorption.
→
reduced muscle perfusion
→
delayed drug absorption.
Drug applied to skin for prolonged systemic delivery
→
transdermal route
→
systemic absorption without initial portal passage.
→
transdermal route
→
systemic absorption without initial portal passage.
Weak base enters a relatively acidic compartment
→
increased ionization
→
reduced membrane return
→
ion trapping.
→
increased ionization
→
reduced membrane return
→
ion trapping.
Oral drug is well absorbed but shows low systemic exposure
→
extensive presystemic metabolism
→
reduced bioavailability.
→
extensive presystemic metabolism
→
reduced bioavailability.
6. High-Yield Exam Points
- ⭐ Pharmacokinetics = body acting on drug; pharmacodynamics = drug acting on body.
- ⭐ Intravenous administration provides complete bioavailability because no absorption step is required.
- ⭐ Sublingual administration gives rapid systemic entry while largely avoiding hepatic first-pass metabolism.
- ⭐ The non-ionized, lipid-soluble form of a drug crosses biological membranes most readily.
- ⭐ AUC represents overall systemic drug exposure and is central to comparing availability.
- ⭐ First-pass metabolism can markedly reduce the amount of unchanged orally administered drug reaching systemic circulation.
- ⭐ Enterohepatic circulation can prolong drug persistence by biliary excretion followed by intestinal reabsorption.