Weekly Pharmacology Exam - April 17, 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

180 — Therapeutic Index (TI) is calculated as LD50/ED50. 200 / 20 = 10.

Question 3

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

Accepted Answer

The dose below which no effect is observed — The threshold dose is the lowest dose at which a particular measurable effect or response first occurs.

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

1.25 — Margin of Safety (MOS) is often calculated as LD01/ED99. 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 — In standard Hodge and Sterner scales, substances with an LD50 between 50-500 mg/kg are categorized as moderately toxic.

Question 6

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

Accepted Answer

The concentration of drug required to produce a specific effect of given intensity — Potency is a measure of the amount of drug (dose/concentration) required to produce an effect of a given magnitude (usually EC50).

Question 7

NOAEL stands for:

Accepted Answer

No Observed Adverse Effect Level — NOAEL is the No Observed Adverse Effect Level, used in toxicology to determine the highest dose that does not produce a significant increase in adverse effects.

Question 8

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

Accepted Answer

100 — TI = TD50 / ED50 = 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 the drug is more potent.

Question 10

Tyramine produces its sympathomimetic effects primarily by which mechanism?

Accepted Answer

Displacing stored norepinephrine from nerve terminals — Tyramine is an indirect-acting sympathomimetic that enters nerve endings via the reuptake transporter and displaces stored norepinephrine.

Question 11

Why is tyramine normally inactive when consumed orally in food?

Accepted Answer

It is rapidly metabolized by MAO-A in the gut and liver — Tyramine is heavily metabolized by Monoamine Oxidase (MAO) Type A in the intestinal wall and liver 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 norepinephrine, causing a dangerous rise in blood pressure.

Question 13

Pharmacodynamics includes the study of:

Accepted Answer

Biochemical and physiological effects of drugs and their mechanisms of action — Pharmacodynamics explains what the drug does to the body (mechanisms and effects), while pharmacokinetics explains 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 liver blood flow and muscle mass — Reduced liver blood flow decreases metabolism, and reduced muscle mass often correlates with reduced renal clearance, necessitating lower doses to avoid toxicity.

Question 15

What does the term 'affinity' mean?

Accepted Answer

The strength of binding 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 but produces no response, preventing agonist binding — Antagonists have affinity for the receptor but zero intrinsic activity (efficacy), thereby blocking agonists.

Question 17

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

Accepted Answer

Covalent bonding — Covalent bonds are strong and stable, making the inhibition irreversible as the drug cannot easily dissociate.

Question 18

Drug receptors are found on:

Accepted Answer

Extracellularly, on the cell surface, and intracellularly — Receptors can be located on the plasma membrane, in the cytoplasm, or in the nucleus (e.g., steroid receptors).

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 via the baroreceptor reflex?

Accepted Answer

Acetylcholine — The baroreceptor reflex responds to high BP by increasing parasympathetic tone, releasing 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 similarly to tyramine, promoting the release of stored norepinephrine into the synapse.

Question 21

Full activation of the sympathetic nervous system (fight-or-flight) occurs during maximal exercise. Which of the following effects is most likely?

Accepted Answer

Mydriasis — Sympathetic activation causes pupillary dilation (mydriasis) to allow more light into the eye.

Question 22

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

Accepted Answer

Hyperthermia and flushed skin — Atropine poisoning is described as 'Hot as a hare, Red as a beet, Dry as a bone, Blind as a bat, Mad as a hatter'—indicating hyperthermia and vasodilation.

Question 23

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

Accepted Answer

Epinephrine — Epinephrine is the first-line treatment for anaphylaxis due to its ability to cause vasoconstriction and bronchodilation.

Question 24

Epinephrine causes a decrease in:

Accepted Answer

Cutaneous blood flow — Epinephrine causes alpha-1 mediated vasoconstriction in the skin and viscera, decreasing cutaneous blood flow.

Question 25

The study of the relationship between drug concentration at the site of action and the resulting effect is called:

Accepted Answer

Pharmacodynamics — Pharmacodynamics focuses on the interaction between drugs and their targets and the resulting physiological effects.

Question 26

A partial agonist is a drug that:

Accepted Answer

Binds to a receptor but cannot produce a maximal response even at high doses — Partial agonists have lower intrinsic activity than full agonists and cannot achieve Emax regardless of concentration.

Question 27

The 'therapeutic window' refers to:

Accepted Answer

The range of doses between the minimum effective concentration and the minimum toxic concentration — The therapeutic window describes the safe range of drug levels that provide clinical benefit without excessive toxicity.

Question 28

Which of the following receptors is a G-protein coupled receptor?

Accepted Answer

Muscarinic receptor — Muscarinic receptors (M1-M5) are GPCRs, whereas nicotinic and GABA-A receptors are ion channels.

Question 29

An example of a physiological antagonist is:

Accepted Answer

Epinephrine antagonizing histamine-induced bronchoconstriction — Physiological antagonism involves two agonists acting on different receptors to produce opposite physiological effects.

Question 30

The ED50 is defined as:

Accepted Answer

The dose that is effective in 50% of the population — The Effective Dose 50 (ED50) in quantal dose-response curves is the dose at which 50% of individuals exhibit the specified effect.

Question 31

Competitive antagonism can be overcome by:

Accepted Answer

Increasing the concentration of the agonist — Because competitive antagonists compete for the same site, increasing agonist concentration can displace the antagonist.

Question 32

Which term describes the maximal effect (Emax) a drug can achieve?

Accepted Answer

Efficacy — Efficacy refers to the maximum intensity of response a drug can produce.

Question 33

The addition of a non-competitive antagonist to an agonist will:

Accepted Answer

Decrease the maximum response (Emax) of the agonist — Non-competitive antagonists bind irreversibly or to an allosteric site, reducing the total available functional receptors and thus decreasing Emax.

Question 34

If a drug has a high Therapeutic Index, it implies:

Accepted Answer

There is a large margin between the effective and toxic doses — A high TI means the toxic dose is much higher than the therapeutic dose, making the drug relatively safe.

Question 35

Spare receptors exist when:

Accepted Answer

The maximum response is achieved at a concentration where not all receptors are occupied — Spare receptors allow for maximal physiological response at low levels of receptor occupancy, increasing sensitivity to agonists.

Question 36

Tachyphylaxis is defined as:

Accepted Answer

A rapid decrease in response to a drug after repeated administration — Tachyphylaxis is an acute, rapid decrease in the response to a drug after its administration.

Question 37

A drug that binds to the same site as the endogenous ligand but produces the opposite pharmacological effect is a(n):

Accepted Answer

Inverse agonist — Inverse agonists reduce the constitutive (baseline) activity of a receptor, producing an effect opposite to the agonist.

Question 38

Which of the following is an example of a Type II (Ionotropic) receptor?

Accepted Answer

Nicotinic Acetylcholine receptor — Nicotinic receptors are ligand-gated ion channels (ionotropic receptors).

Question 39

The term 'EC50' refers to:

Accepted Answer

The concentration of a drug that produces 50% of the maximal effect — EC50 is the 'half-maximal effective concentration' used to measure potency in a graded dose-response curve.

Question 40

In the presence of a non-competitive antagonist, the agonist's log dose-response curve will show:

Accepted Answer

A decrease in the slope and a reduction in the maximum height (Emax) — Non-competitive antagonists reduce the maximum efficacy (downward shift) and cannot be overcome by more agonist.

Question 41

Quantal dose-response curves are used to determine:

Accepted Answer

The percentage of a population that shows an all-or-none response — Quantal responses are 'all-or-none' (e.g., sleep/no sleep, dead/alive) and are used to see population distributions.

Question 42

Which of the following best defines an 'antidote'?

Accepted Answer

A substance that neutralizes or counteracts the effects of a poison — Antidotes counteract toxins through various chemical, pharmacological, or physiological mechanisms.

Question 43

A substance with an LD50 of 5 mg/kg is categorized as:

Accepted Answer

Extremely toxic — LD50 values less than 5-10 mg/kg are typically classified as extremely toxic.

Question 44

Which of the following describes 'chemical antagonism'?

Accepted Answer

A drug reacting chemically with another drug to form an inactive complex — Chemical antagonism (e.g., chelating agents) occurs when the antagonist reacts directly with the agonist/toxin to neutralize it.

Question 45

Down-regulation of receptors usually occurs after:

Accepted Answer

Chronic use of an agonist — Continuous stimulation of receptors by agonists often leads to a decrease in receptor number or sensitivity (desensitization).

Question 46

Up-regulation or super-sensitivity is often a result of:

Accepted Answer

Chronic exposure to an antagonist — Chronic blockade of receptors leads the cell to increase receptor density to maintain signaling.

Question 47

What is the primary characteristic of an Intracellular Receptor?

Accepted Answer

It must be activated by lipid-soluble ligands — To reach intracellular receptors (cytoplasmic or nuclear), ligands must be lipid-soluble to cross the plasma membrane.

Question 48

In pharmacology, 'intrinsic activity' is a measure of:

Accepted Answer

The drug's ability to activate the receptor and produce a response — Intrinsic activity (efficacy) is the property that distinguishes agonists from antagonists.

Question 49

The study of how drugs move through the body (absorption, distribution, metabolism, excretion) is:

Accepted Answer

Pharmacokinetics — Pharmacokinetics (PK) describes the movement of the drug through the body.

Question 50

Which of the following is most likely to cause a 'Cholinergic Crisis'?

Accepted Answer

Organophosphate insecticides — Organophosphates inhibit acetylcholinesterase, leading to a massive buildup of acetylcholine.

Weekly Pharmacology Exam - April 17, 2026 (Section A: MCQs)

Questions, Answers & Explanations