Weekly Pharmacology Exam - April 21, 2026 (Section A: MCQs)

Question 1

A patient receives a drug dose of 500 mg daily. To express this dose normalized to body weight for a 70 kg patient, what unit would be most appropriate?

Accepted Answer

mg/kg — Normalizing a dose to body weight is standardly expressed as mg of drug per kg of body weight (mg/kg).

Question 2

The LD50 of a new compound is determined to be 200 mg/kg, while its ED50 is 20 mg/kg. What is the Therapeutic Index (TI) of this drug?

Accepted Answer

220 — Therapeutic Index (TI) = LD50 / ED50. In this case, 200 / 20 = 10.

Question 3

Which of the following best describes the 'threshold dose' in a dose-response relationship?

Accepted Answer

The lowest dose at which a measurable effect is first observed — The threshold dose is the point on a dose-response curve where a response first begins to occur.

Question 4

A drug has an LD01 of 100 mg/kg and an ED99 of 80 mg/kg. What is the Margin of Safety (MOS)?

Accepted Answer

0.8 — The Margin of Safety is often calculated as LD01 / ED99. Here, 100 / 80 = 1.25.

Question 5

According to toxicity scales, a substance with an LD50 of 400 mg/kg would be classified as:

Accepted Answer

Moderately toxic — Substances with LD50 between 50-500 mg/kg are generally classified as moderately toxic.

Question 6

In dose-response curves, 'potency' refers to:

Accepted Answer

The concentration or dose of a drug required to produce a specific effect — Potency is a measure of the amount of drug needed to produce an effect of a given intensity (often measured by EC50).

Question 7

NOAEL stands for:

Accepted Answer

No Observed Adverse Effect Level — NOAEL (No Observed Adverse Effect Level) is the highest dose at which no statistically significant adverse effect is found.

Question 8

A drug with TD50 of 150 mg and ED50 of 50 mg would have what Therapeutic Index?

Accepted Answer

0.33 — TI = TD50 (Toxic Dose) / ED50 (Effective Dose). 150 / 50 = 3.

Question 9

When comparing two drugs on a dose-response curve, if Drug A's curve is shifted to the left of Drug B's curve, this indicates:

Accepted Answer

Drug A is more potent than Drug B — A leftward shift on the x-axis (dose) indicates that a lower dose is required to achieve the same effect, meaning higher potency.

Question 10

Tyramine produces its sympathomimetic effects primarily by which mechanism?

Accepted Answer

Displacing stored norepinephrine from synaptic vesicles — Tyramine is an indirect-acting sympathomimetic that causes the release of stored catecholamines.

Question 11

Why is tyramine normally inactive when consumed orally in food?

Accepted Answer

It is rapidly metabolized by MAO-A in the gut wall and liver — Dietary tyramine is normally broken down by Monoamine Oxidase (primarily MAO-A) in the GI tract before reaching systemic circulation.

Question 12

A patient taking a nonselective MAO inhibitor consumes aged cheese containing high tyramine levels. What is the most likely consequence?

Accepted Answer

Hypertensive crisis — MAO inhibitors prevent the breakdown of tyramine, leading to massive release of endogenous norepinephrine, causing a hypertensive crisis.

Question 13

Pharmacodynamics includes the study of:

Accepted Answer

Biochemical and physiological effects of drugs and their mechanisms of action — Pharmacodynamics deals with what the drug does to the body (mechanisms and effects), while pharmacokinetics deals with what the body does to the drug.

Question 14

Which of the following physiological changes in the elderly may lead to the need to reduce the dose of a prescribed medication?

Accepted Answer

Decreased glomerular filtration rate — Reduced renal function (GFR) in the elderly reduces the clearance of many drugs, necessitating dose reduction to avoid toxicity.

Question 15

What does the term 'affinity' mean in pharmacology?

Accepted Answer

The strength of the bond between a drug and its receptor — Affinity refers to the tendency of a drug to bind to a specific receptor.

Question 16

A pharmacological antagonist is a drug that:

Accepted Answer

Binds to a receptor without activating it and prevents agonist binding — Antagonists have affinity but zero intrinsic activity; they block the receptor from being activated by agonists.

Question 17

Irreversible inhibition of a receptor or enzyme is typically due to:

Accepted Answer

Covalent bonding — Covalent bonds are strong and stable, often resulting in permanent (irreversible) inhibition until new proteins are synthesized.

Question 18

Drug receptors are found on:

Accepted Answer

Both the cell surface and intracellularly — Receptors can be transmembrane G-protein coupled receptors, ion channels, or intracellular (nuclear) receptors like those for steroid hormones.

Question 19

Which of the following is the neurotransmitter agent normally released in the sinoatrial node (SAN) of the heart in response to an increase in blood pressure?

Accepted Answer

Acetylcholine — Increased BP triggers the baroreceptor reflex, leading to parasympathetic (vagal) release of Acetylcholine to slow the heart rate.

Question 20

Which of the following drugs facilitates catecholamine transmitter release from adrenergic nerve endings?

Accepted Answer

Amphetamine — Amphetamines act by increasing the release of norepinephrine and dopamine from presynaptic terminals.

Question 21

Full activation of the sympathetic nervous system (fight-or-flight) during maximal exercise will most likely result in:

Accepted Answer

Dilation of bronchioles — Sympathetic activation causes bronchodilation via beta-2 receptors to improve air flow during exercise.

Question 22

Probable signs of atropine overdose in toddlers include which one of the following?

Accepted Answer

Hyperthermia and flushed skin — Atropine poisoning is characterized by 'Red as a beet, Dry as a bone, Blind as a bat, Mad as a hatter, and Hot as a hare'.

Question 23

Which is the treatment of choice in a child with signs of anaphylaxis after being stung by bees?

Accepted Answer

Epinephrine intramuscularly — Epinephrine is the first-line treatment for anaphylaxis due to its ability to cause vasoconstriction, bronchodilation, and decreased mediator release.

Question 24

In the cardiovascular system, Epinephrine causes a decrease in:

Accepted Answer

Total peripheral resistance (at low doses) — At low doses, epinephrine's beta-2 effect (vasodilation) predominates over alpha-1, leading to a decrease in peripheral resistance.

Question 25

The LD50 of a compound is 1000 mg/kg and the ED50 is 10 mg/kg. The Therapeutic Index is:

Accepted Answer

0.01 — TI = 1000 / 10 = 100.

Question 26

A drug that provides a maximal response while occupying only a small fraction of available receptors is said to have:

Accepted Answer

Spare receptors — Spare receptors exist when the maximal response is achieved with less than total receptor occupancy.

Question 27

Pharmacokinetics includes the study of:

Accepted Answer

Absorption, Distribution, Metabolism, and Excretion — ADME is the foundation of pharmacokinetics.

Question 28

Competitive antagonists shift the agonist dose-response curve in which direction?

Accepted Answer

To the right, without changing the maximum response — Competitive antagonists can be overcome by increasing the agonist concentration, resulting in a rightward shift of the ED50.

Question 29

Non-competitive antagonists change the dose-response curve of an agonist by:

Accepted Answer

Reducing the maximum response (Emax) — Non-competitive antagonists bind irreversibly or to an allosteric site, meaning no amount of agonist can restore the full Emax.

Question 30

A partial agonist is characterized by:

Accepted Answer

High affinity but lower maximal effect compared to a full agonist — Partial agonists have intrinsic activity less than 1, meaning they cannot produce the same Emax as a full agonist even at saturation.

Question 31

Which route of administration has the highest bioavailability typically?

Accepted Answer

Intravenous — Intravenous (IV) administration bypasses absorption barriers and first-pass metabolism, offering 100% bioavailability by definition.

Question 32

The primary site of drug metabolism is the:

Accepted Answer

Liver — The liver contains the highest concentration of metabolic enzymes like Cytochrome P450.

Question 33

Biotransformation Phase I reactions include:

Accepted Answer

Oxidation — Phase I reactions convert parent drugs into more polar metabolites via oxidation, reduction, or hydrolysis.

Question 34

Biotransformation Phase II reactions typically involve:

Accepted Answer

Conjugation with polar molecules — Phase II reactions are conjugation reactions (e.g., glucuronidation, acetylation) that make drugs more water-soluble for excretion.

Question 35

The 'First-Pass Effect' refers to:

Accepted Answer

Metabolism of a drug before it reaches systemic circulation — Orally administered drugs go through the portal vein to the liver, where they may be extensively metabolized before reaching the heart and rest of the body.

Question 36

What is the half-life (t1/2) of a drug?

Accepted Answer

The time required for the plasma concentration to decrease by 50% — Half-life is the time required for the concentration of a drug in the plasma to fall to half of its initial value.

Question 37

A drug with a narrow therapeutic index requires:

Accepted Answer

Frequent dose adjustments and plasma level monitoring — Narrow TI drugs (e.g., lithium, digoxin, warfarin) have toxic doses very close to effective doses, requiring Therapeutic Drug Monitoring (TDM).

Question 38

Induction of Cytochrome P450 enzymes usually results in:

Accepted Answer

Decreased plasma levels of co-administered drugs — Enzyme induction speeds up the metabolism of drugs, thereby lowering their therapeutic concentrations.

Question 39

Inhibiting Cytochrome P450 enzymes can lead to:

Accepted Answer

Increased risk of toxicity for co-administered drugs — Inhibition slows metabolism, causing the drug to accumulate and potentially reach toxic levels.

Question 40

The main neurotransmitter of the parasympathetic nervous system is:

Accepted Answer

Acetylcholine — Acetylcholine (ACh) is the neurotransmitter for both preganglionic and postganglionic parasympathetic neurons.

Question 41

Muscarinic receptors are primarily located on:

Accepted Answer

Effector organs of the parasympathetic system — Muscarinic receptors mediate the effects of ACh on smooth muscle, cardiac muscle, and glands.

Question 42

Nicotinic receptors are found in:

Accepted Answer

Neuromuscular junctions and autonomic ganglia — Nicotinic receptors are ionotropic receptors found at NMJs (Nm) and autonomic ganglia/adrenal medulla (Nn).

Question 43

Which of the following is a clinical use for Atropine?

Accepted Answer

Treatment of Sinus Bradycardia — Atropine blocks muscarinic receptors in the heart, increasing the heart rate by blocking vagal tone.

Question 44

Pilocarpine is used clinically to treat:

Accepted Answer

Glaucoma — Pilocarpine is a muscarinic agonist that causes miosis and contraction of the ciliary muscle, facilitating drainage of aqueous humor.

Question 45

Neostigmine acts by:

Accepted Answer

Inhibiting Acetylcholinesterase — Neostigmine is an anticholinesterase agent that increases the concentration of ACh at the synapse.

Question 46

Specific antidote for Organophosphate (nerve gas) poisoning is:

Accepted Answer

Pralidoxime (2-PAM) — Pralidoxime acts to 'regenerate' the inhibited acetylcholinesterase enzyme if given before 'aging' occurs.

Question 47

Alpha-1 adrenergic receptors predominantly cause:

Accepted Answer

Vasoconstriction — Alpha-1 receptors are located on vascular smooth muscle and cause contraction (vasoconstriction) when stimulated.

Question 48

Beta-1 adrenergic receptors are located primarily in the:

Accepted Answer

Heart — Beta-1 receptors increase heart rate (chronotropy) and contractility (inotropy).

Question 49

Beta-2 adrenergic receptor stimulation leads to:

Accepted Answer

Bronchodilation — Beta-2 receptors cause relaxation of smooth muscles in the bronchioles and blood vessels of skeletal muscle.

Question 50

A patient with asthma should avoid which type of medication?

Accepted Answer

Non-selective beta-blockers — Non-selective beta-blockers (like Propranolol) can block beta-2 receptors in the lungs, leading to life-threatening bronchospasm.

Weekly Pharmacology Exam - April 21, 2026 (Section A: MCQs)

Questions, Answers & Explanations