Pharmacokinetics + dynamics

Question 1

2. With regard to a drug:
   a. LD50 is 50% of the dose necessary to kill experimental animals
   b. Efficacy is the maximum response produced by a drug

Answer 1

B: “In pharmacology, efficacy refers to the maximum response achievable from a drug. It is often described by the parameter Emax.”

Question 2

4. 2mL of 0.5% wv is equal to
   a. 1mg
   b. 10mg
   c. 100mg
   d. 20mg

Answer 2

b. 10mg – 0.1% = 1:1000 = 1mg/ml, so 0.5% = 5mg x 2 ml = 10mg

Question 3

5. What is an example of a phase II biotransformation?
   a. Oxidation
   b. Reduction
   c. Glycolysis
   d. sulfation

Answer 3

d.
The phase II rections are glucuronidation, acetylation, glutathione conjugation, glycine conjugation, sulfation, methylation, water conjugation

Question 4

6. Regarding enzyme induction
   a. It is irreversible
   b. It takes 4 months to develop
   c. Causes increase in smooth endoplasmic reticulum
   d. Causes increase in rough endoplasmic reticulum

Answer 4

c

Question 5

8. Regarding pharmacokinetics and pharmacodynamics
   a. Diffusion is inversely proportionate to surface area and directly proportionate to thickness
   b. The LD50 is 50% of the dose that kills most people
   c. The LD50 is 50% of the dose at which toxicity occurs
   d. Efficacy is the maximum response produced by a drug

Answer 5

d

Question 6

10. Volume of distribution
    a. Is inversely proportional to clearance
    b. Is measured in mg/L
    c. Is used to work out the maintenance dose
    d. Is high in warfarin
    e. Is proportional to half life

Answer 6

e

Question 7

11. 5mL of 2% wv is equal to:
    a. 10mg
    b. 100mg
    c. 200mg
    d. 20mg
    e. 40mg

Answer 7

b. 100mg 0.1% = 1:1000 = 1mg/mL, thus 2% = 20mg x 5mL = 100mg

Question 8

12. Volume of distribution
    a. Is calculated by dividing the amount of drug by its clearance
    b. If high suggests homogeneous distribution through tissues
    c. If low suggests homogeneous distribution through tissues
    d. Of aspirin is greater than that of pethidine
    e. Of midazolam is greater than that of warfarin

Answer 8

e

Question 9

13. The volume of distribution
    a. Is less than 70L for fluoxetine
    b. Is calculated by dividing rate of elimination by concentrarion
    c. Is inversely proportional to half life
    d. Is about 5L/kg for pethidine
    e. Is affected by the route of drug administration

Answer 9

d

Question 10

14. By limiting liver blood flow, cardiac disease might inhibit the metabolism of all of the following EXCEPT:
    a. Verapamil
    b. Labetalol
    c. Propoxyphene
    d. Lignocaine
    e. Trimethoprim

Answer 10

e
… other drugs with 100% bioavailability are: chlordiazepoxide, diazepam, lithium, phenobarbital, salicylic acid, sulfamethoxazole, valproic acid

Question 11

15. The bioavailability of a drug
    a. Must be 100% if given by inhalation
    b. Is typically about 75% for IV administration
    c. Is high if the drug is hydrophilic
    d. Is equal to 1- the extraction ratio
    e. Is 70% for orall administered digoxin

Answer 11

e

Question 12

16. For a specific effect, drug A is more potent than drug B. It follows that:
    a. Drug B is a partial agonist acting at the same receptor as drug A
    b. Drug A causes a greater maximal effect than drug B
    c. When present in identical concentrations, drug A causes a greater effect than drug B
    d. Drug A has a lower ED50 than drug B
    e. Drug B will have a steeper dose response curve than drug A

Answer 12

d- this is the definition of potency

Question 13

17. The volume of distribution of a drug:
    a. Relates its dose to its clearance
    b. Is not an apparent volume
    c. If high, implies greater concentration of drug in extravascular tissue
    d. If high, implies greater plasma protein binding of the drug
    e. If high, implies easier clearance of the drug by haemodialysis in overdose

Answer 13

c

Question 14

18. Regarding receptors, the following statements are true EXCEPT:
    a. Most are proteins
    b. They largely determine quantitative relations between dose of a drug and pharmacologic effect
    c. They are responsible for selectivity of a drug reaction
    d. Mediate actions of pharmacologic antagonists
    e. Spare receptors produce effect without the need for a drug

Answer 14

e

agonisism still required, just more sensitive

Question 15

19. Regarding elimination kinetics, which statement is INCORRECT?
    a. In first-order kinetics, the rate of elimination is directly proportional to drug concentration
    b. Ethanol displays dose-dependent kinetics
    c. In zero-order kinetics, the rate of elimination is constant
    d. Most drugs display first-order kinetics
    e. Phenytoin can display zero-order kinetics

Answer 15

b

Question 16

20. For a drug that is present in a concentration 4 times its EC50
    a. The time course of effect is linear, initially
    b. The time course of effect will follow the exponential decline in concentration
    c. Toxicity can be expected
    d. All of the above may be true depending on the drug
    e. Toxicity would not be expected

Answer 16

a

Question 17

21. All of the following statements about spare receptors are correct EXCEPT:
    a. Spare receptors are identical, in the absence of drug, to non spare receptors
    b. Spare receptors do not bind drug when the maximal drug effect occurs
    c. Spare receptors influence the sensitivity of the receptor system to the drug
    d. Spare receptors activate the effector machinery of the cell without the need for a drug
    e. Spare receptors may be detected by finding that the EC50 is less than the Kd for the agonist

Answer 17

d

Question 18

22. Which of the following drug metabolising systems has been shown to differ in populations in genetically pre-determined ways?
    a. Reductions
    b. Acetylations of amines
    c. Methylation
    d. Glucuronidation
    e. Sulfate conjugation

Answer 18

b
– isoniazid -> peripheral neuropathy, also oxidation (codeine -> reduced analgesia, EtOH -> toxicity, nortriptyline -> toxicity, s-warfarin -> bleeding), ester hydrolysis (succinylcholine -> prolonged apnea), o-demethylation (omeprazole -> increased efficacy)

Question 19

23. Regarding receptor action
    a. High concentrations of an agonist can never surmount a competitive antagonist
    b. Partial agonists do not occupy all receptor sites
    c. EC50 refers to the clinical effect at 50% of the maximal dose
    d. Second messengers explain “spare receptors”
    e. B-blockers and adrenaline exhibit physiological antagonism

Answer 19

d

Question 20

24. Half-life
    a. Is inversely proportional to Vd (volume of distribution)
    b. Is the time required to attain 50% of steady-state concentration
    c. Is directly proportional to clearance
    d. Is decreased in renal failure
    e. Is decreased in hepatic failure

Answer 20

b

Question 21

25. Regarding bioavailability
    a. Rectal administration has the same first-pass effect as oral
    b. Transdermal is up to 90%
    c. IV administration is between 95 and 100%
    d. Is reduced in digoxin when given orally because of bacterial metabolism
    e. Can be calculated by the extence of absorption (f) multiplied by the extraction ratio (ER)

Answer 21

d

Question 22

26. Regarding biotransformation
    a. Phase I reactions lead to increased polarity for excretion by the liver
    b. Phase I reactions occur solely in the liver
    c. Phase I reactions must undergo phase II reactions in order to be renally excreted
    d. Hydroxylation and deamination are examples of phase I reactions
    e. Rarely leads to toxic metabolites

Answer 22

d

Question 23

27. The potency of a drug
    a. Refers to the concentration needed to produce maximal effects
    b. Depends on the efficiency of drug-receptor interaction
    c. Is the limit of the dose-response relation
    d. Determines clinical efficacy
    e. Determines its toxic side-effects

Answer 23

b

Question 24

28. The volume of distribution
    a. Is proportionately related to the concentration of crug in the body
    b. Is high for those drugs retained in the vascular compartment
    c. Is a measure of the apparent space available in the body to contain a drug
    d. For chloroquine is much smaller than that of digoxin
    e. None of the above

Answer 24

c

Question 25

29. Phase II reactions in metabolic biotransformation include all of the following EXCEPT: a. Water conjugation b. Cytochrome P-450 dependent oxidations c. Acetylation d. Methylation e. Glucuronidation

Answer 25

b

Question 26

30. An example of a drug receptor includes: a. Leukotriene-B (LTB) b. Tubulin c. Arachinodic acid d. Fibronectin e. Tumour necrosis factor -1

Answer 26

b

Question 27

31. The volume of distribution of a drug a. Related the amount of a drug in the body to its plasma concentration b. Is large for a drug extensively bound to plasma proteins c. Is large for aspirin d. Never exceeds 42 litres e. Is not affected by albumin concentration

Answer 27

a

Question 28

32. Receptor antagonists a. Prevent agonists from binding to antagonists b. Progressively inhibit agonist response to decreasing concentrations of antagonist c. Cannot be negated at high doses of agonists d. Bind to the receptor and activate it e. Inhibit receptors to a degree proportionate to antagonist concentration

Answer 28

e

Question 29

33. Regarding second messengers a. cAMP has no role in calcium homeostasis b. cAMP exerts most of its effects by stimulating cAMP-dependent protein kinases c. inhibition of adenylyl cyclase results in increased cAMP d. phospholipase C is situated in the cell nucleus e. phospholipase C catalyses IP3 into PIP2 and DAG

Answer 29

b

Question 30

34. The volume of distribution of a drug: a. Relates the amount of a drug in the body to its plasma concentration b. Is large for a drug extensively bound to plasma proteins c. Is large for aspirin d. Never exceeds 42 litres e. Is not affected by albumin concentration

Answer 30

a

Question 31

35. Type I biotransformation reactions include: a. Methylation b. Acetylation c. Oxidation d. Glucuronidation e. Sulphonation

Answer 31

c

Question 32

5. What is the half life of a drug with a volume of distribution of 100ℓ/70kg and a clearance of 7ℓ/hr/70kg a. 5 hours b. 10 hours c. 12.5 hours d. 15 hours e. 20 hours

Answer 32

b

Question 33

11. EC50 is a. Measured with a radioactive receptor b. Always equal to Kd c. Drug concentration with 50% receptors bound d. Representation of the receptors affinity for drug binding e. Drug concentration with 50% of maximal drug effect

Answer 33

e

Question 34

12. Which of the following will NOT alter the volume of distribution of a drug? a. Cardiac failure b. Clearance c. Age d. Burns e. Pleural effusion

Answer 34

b

Question 35

13. Volume of distribution equals a. Dose given/plasma concentration b. Total amount of drug in the body/plasma concentration c. Urine drug concentration/plasma concentration d. Dose given/urine concentration e. Urine drug concentration/plasma concentration

Answer 35

b

Question 36

15. Ligand gated channel receptors include all of the following EXCEPT a. GABA b. Aspartate c. Glycine d. Glutamate e. Ach-muscarinic

Answer 36

e

Question 37

16. Regarding receptor regulation a. Receptor down regulation occurs over hours – days b. Receptor responses to drugs often “desensitise” with time – this desensitisation is usually irreversible c. The mechanism of agonist induced desensitisation of the nicotinic Ach receptor has been worked out in detail d. All “internalised” receptors are degraded by lysosomes e. None of the above are correct

Answer 37

a

Question 38

17. Which of the following acts on intracellular receptors a. Serotonin b. Glucagon c. Corticosteroids d. GABA e. Insulin

Answer 38

c

Question 39

19. First order kinetics a. Means rate of reaction is proportional to concentration b. Are more common than zero order kinetics c. Apply to exponential processes d. Generally apply to high plasma concentrations (>20mg/100ml) of ethanol e. Result in steady state concentrations after multiple dosing

Answer 39

d

Question 40

20. A single compartment model means that a. One exponential term describes the decreasing plasma concentration of the drug b. A single exponential term describes the rise in plasma concentration following oral administration c. The drug does not penetrate tissues d. The drug is restricted to the ECF e. The drug is highly ionised

Answer 40

a