Pharmacokinetics MCQs

Q1. What kind of substances can’t permeate membranes by passive diffusion?

a) Lipid-soluble

b) Non-ionized substances

c) Hydrophobic substances

d) Hydrophilic substances

Ans: d) Hydrophilic substances

• Only lipid soluble/lipophilic/hydrophobic drugs can absorb by passive diffusion process
• And Watersoluble/hydrophilic drugs can absorb by pore transport or carrier mediated transport system

Q2. What is implied by «active transport»?

a) Transport of drugs trough a membrane by means of diffusion

b) Transport without energy consumption

c) Engulf of drug by a cell membrane with a new vesicle formation

d) Transport against concentration gradient

Ans: d) Transport against concentration gradient

Carrier Mediated Transport system: transportation through a Carrier Protein, Therefore it is a Saturable process

• Active Transport: Uphill Process, means drugs move low concentration to high concentration against concentration gradients and this process require an energy. Thus it is an Energy dependent process
• Facilitate Transport: Downhill Process, towards concentration gradients, energy independent

Q3. What is right for carrier mediated transport system ??

a) Transport against concentration gradient

b) Saturable process

c) Energy dependent

d) Obey Fick’s first law

Ans: b) Saturable process

• As discussed previous carrier mediated transport system is a saturable process
• Options A & B are true only for Active transport not for Facilitated transport
• And only lipid diffusion obeys the Fick’s first law

Q4. What does the term “bioequivalence” mean?

a) Plasma protein binding degree of substance

b) Similar bioavailability of a same drug preparation from different company.

c) Similar bioavailability of a different drug preparation from same company.

d) Fraction of an uncharged drug reaching the systemic circulation following any route administration

Ans: b) Similar bioavailability of a same drug preparation from different company.

Bioavailability: The amount of the drug reaches the systemic circulation from the site of action in an unchanged form is known as bioavailability.

Relative B. A. (%) = [(AUC)o/(AUC)iv] x 100

F (%) =  (PC_Oral/PC_iv) x 100

Q5. For the better therapeutic effect 50 mg of a drug should be present in the blood, and it has 25% of bioavailability than what should be oral dose.

a) 50 mg

b) 100 mg

c) 200 mg

d) 12.5 mg

Ans: c) 200 mg

F = PC(oral)/PC(iv) =Mass(oral)/Mass(iv)

F = M(absorbed)/M(administered)

Where F = 0.25 (25%), Mass(abs)= 50 mg

Mass (adm) = Mass (abs)/F

Mass (adm)= 50/0.25 = 200

Q6. if drug pKa is 4 and pH media is 7 then

a) 99.9 % drug is ionized

b) 99.99 % drug is ionized

c) 99% drug is ionized

d) 90% drug is ionized

Ans: b) 99.9 % drug is ionized

• Degree of ionization is determined by “Handersen-Hasselbach equation”
  • For weak acids: pH-pKa = log (ionized drug /unionized drug)
  • For weak bases: pH-pKa = log (unionized drug / ionized drug)

*pKa – the value of pH in which drugs have 50 % ionised and 50% unionised.

• Ionization of weak acid drug increases with pH of the media and ionization of weak basic drug decreases with pH
  • Acid drug + Base Media = Ionization (Poorly Absorbed)
  • Acid drug + Acid media = Union (better absorbed)
  • For Week Acid (Pka<7)

Q7. If the pKa of phenobarbitone is 3.4, what fraction of drug would be ionized at pH 4.4?

(a) 0.01                            

(b) 0.5

(c) 0.9                             

(d) 1

Ans: (c) 0.9  or 90% 

pH-pKa = 4.4-3.4 = 1 === 90 % ionized (90/100 = 0.9)

Q8. Very weak bases (pKa = 5.0) nature drug absorbed in which of the following part in our body?

(a) Stomach           

(b) Intestine

(c) Colon                

(d) Entire length of GIT

 Ans: (d) Entire length of GIT

In this type of question don’t look at the pKa value just read the sentence  “Very weak bases”

Remember the concepts:

• Strong Acid/Base = not absorb, entire the GIT
• Weak Acid = Absorbed in Stomach
• Weak Base = Absorbed in Intestine
• Very Weak Acid/Base : Absorbed, Entire length of GIT

Q9. if drug pKa is 5 then it is better absorbed in pH….. media

a) 1

b) 3

c) 5

d) 8

 Ans: a) 1

• Acidic drug (pKa<7) is better absorbed in acid media (lower pH) because ionization is minimum in acidic media (Acid + Acid = higher union Fractions)

Q10. The drug is affected by first pass metabolism “except”

a) Opoids

b) Ametryptiline

c) Propranolol

d) Rebeprazole

 Ans: d) Rebeprazole

First Pass Metabolism: Presystemic Elimination

First pass metabolism is the major disadvantage in oral route. It reduce the bioavailability. E.g.

• V = Verapamil
• P = Propranolol
• Singh = Salbutamol
• Not = nitroglycerine
• A = Amitryptiline
• Popular = Propoxyphen
• P = Pethidine
• M = Methyl testosterone
• Others= Opoids, beta blockers, nitrates, and steroids.

Q11. Neurotransmitter(NTs) release is the process of

a) Pinnocytosis

b) Phagocytosis

c) Exocytosis

d) Transcytosis

Ans: C) Exocytosis

• Exocytosis: NTs Vessicle release
• Endocytosis: ingestion/Engulfing of solid/liquid material by cell
  • Pinnocytosis: Cell Drinking
  • Phagocytosis: Cell eating
• Transcytosis: Transcytosis (also known as cytopempsis) is a type of transcellular transport (Exo+Endocytosis)

Q12. The applicability of Noyes-Whitney equation is to describe the

(a) First-order kinetics                           

(b) Zero-order kinetics

(c) Mixed-order kinetics                         

(d) Dissolution rate

Ans: (d) Dissolution rate

Q13. Higher absorption of drug through small intestine is due to

(a) Kekckring                    

(b) Villi

(c) Microvilli            

(d) None of above

Ans: (c) Microvilli -Larger Surface Area

Q14. Micronization of hydrophobic drug decrease solubility of drug This is because

(a) Drug adsorbs air on to their surface

(b) Particles reaggregate to form larger particle

(c) Surface charges may prevent wetting

(d) All of above

Ans: (d) All of above

Q15. Which of the following polymorphic form of drug has the highest solubility of drug

(a) Amorphous                 

(b) Metastable

(c) Stable                         

(d) Hydrated

Ans: (a) Amorphous

Amorphous form has higher dissolution rate as compared to Crystalline form

Q16.Drugs are distributed between central compartment and Tissue compartment through…………………barrier  ?

a) Blood Brain barrier

b) Placental Barrier

c) Capillary/Endothelial Barrier

Ans: c) Capillary/Endothelial Barrier

Q17. Which is not affect the drug distribution process

a) Protein binding

b) Blood perfusion

c) Both

d) None

Ans: d) None

Factors Affecting the Distribution of Drugs:

• Diffusion Rate
• The Affinity of the Drug to the Tissue Components
• Blood Flow (Perfusion Rate)
• Binding to Plasma Proteins

Q18. What is wrong about Plasma Protein Bounded Drug??

a) Provide temporary Storage

b) Therapeutically inactive

c) Unavailable for elimination

d) Enhance the elimination rate

Ans: d) Enhance the elimination rate

Q19. Acidic drugs are mainly bind with…….?

a) Albumin

b) Glycoproteins

c) Lipoproteins

d) Globulin

Ans: a) Albumin

• Albumin: Acidic drug (Salicylates, vitamin C, sulfonamides, barbiturates, penicillin)
• Alfa Acid Glycoprotein: Basic Drugs (streptomycin, chloramphenicol, LA, TCAs)
• Lipoproteins:
  • Acidic- Diclofenac
  • Neutral- Cyclosporin A
  • Basic- Chlorpromazin
• Globulines
  • α-1 (Transcortin)- Corticosteroids, thyroxine, cynocobalamine
  • α-2 (Ceruloplasmin)- Vit A, D, E, K
  • β-1 (Trasferin)- Fe2+
  • β-2 – Caritinoids
  • γ-globulin- Antigens

Q20. Redistribution occurs when:

a) Drug has high water solubility

b) Drug has low Vd

c) Drug has high Ko/w partition coefficient

d) Drug has high protein binding

Ans: c) Drug has high Ko/w partition coefficient –Lipophilic drug

Redistribution:

• Some drugs (especially general anesthetics) which are very lipophilic, following the injection, firstly (initially) distributes to the well-perfused organs like central nervous system..
• Later, the distribution occurs to less perfused organs like muscles.
• At last, distribution of these drugs shifts to the very low-perfused tissues like adipose (fat) tissue

Q21. if the 6000 ug of drug given via iv route to the patient and his plasma drug concentration is 0.2 mg/ml, then Vd is:

a) 0.03L

b) 30 L

c) 30000 L

d) 300 L

Ans: a) 0.03L

Vd (Volume of Distribution, L) = X (mg)/Pc (mg/L)

Here X = 6000ug = 6mg

Pc = 0.2 mg/ml = 200 mg/L

Vd = 6/200 = 0.03 L

Q22. If the required therapeutic plasma conc. of a drug is 5 mg/L and Vd of this drug is 10 L than what should be loadind dose-

a) 5 mg

b) 50 mg

c) 500 mg

d) 5g

Ans: b) 50 mg

Vd = X/Pc

X = Vd x Pc,  Here Vd = 10L, and Pc = 5mg/L

X= 10 x 5 = 50 mg

Q23. what is wrong about Vd (Volume of Distribution)

a) Vd of a drug helps to calculate the loading dose

b) High Vd causes the tissue accumulation

c) Low Vd means drug has higher affinity for the plasma proteins

d) None

Ans: d) None, Means all sentences are correct for the Vd

Case: IV dose 10 mg, plasma vol. 2.5L and 7.5L tissue volume then calculate Vd    (Vd = X/PC) at –

• At 0 time, 100 % drugs are present on blood

                    PC₀ = 10/2.5 = 4mg/L then Vd₀ = 10/4 = 2.5L

• At time t, 25 % drugs are present on blood

                    PC_t = 2.5/2.5 = 1mg/L then Vd_t = 10/1 = 10 L

• High Vd (>20L) means Tissue Accumulation and causes toxicity (highly lipid soluble drugs).
• Low Vd (<10L) means drug drugs are present in intracellular fluid (blood).

Q24. What is wrong about BIOTRANSFORMATION?

1. It is Elimination process
2. Bio-Chemical alteration of Xenobiotic
3. Detoxification Process
4. Saturable process
5. All sentence is correct

Ans: e) All sentence is correct

Biotransformation: The process of Bio-Chemical alteration of a drug/Xenobiotic within the biological system is known as the Biotransformation. It is also known as the drug metabolism and it is an elimination process.

Biological alteration: activation, inactivation, toxic metabolite formation

Chemical alteration: lipophilic to hydrophilic

Q25. Microsomal oxidation required EXCEPT:

a) Reactive oxygen

b) NADPH2

c) Cyp-450-Fe3+

d) NADP⁺

 Ans: d) NADP⁺

Phase I Reaction: metabolic alteration process

Mainly: Oxidation, Reduction, and Hydrolysis

Microsomal Oxidation Reaction:

RH + O2 + NADPH2    à ROH + H2O + NADP⁺

Q26. Pick out the right statement:

a) Microsomal oxidation always results in inactivation of a compound

b) Microsomal oxidation results in a decrease of compound toxicity

c) Microsomal oxidation results in an increase of ionization and water solubility of a drug

d) Microsomal oxidation results in an increase of lipid solubility of a drug thus its excretion from the organism is facilitated

Ans: c) Microsomal oxidation results in an increase of ionization and water solubility of a drug

Q27. Which isoenzyme is mostly involved in the drug metabolism

a) CYP3A4

b) CYP2D6

c) CYP2E1

d) CYP2C9

Ans: a) CYP 3A4

Q28. Omeperazole can ……………………the metabolic enzymes

a) Inhibit

b) induce

ANS: a) Inhibit

• INDUCER (P C BAR PG)= Phenytoin, Carbamezapine, Barbiturates, Alcohal, Rifampicin, Phenylbutazone, Griseofulvin.
• INHIBITOR (COKE PI) = Cemitidine, Omeperazole, Ketakonazole, Erythromycin, Protease Inhibitor (Saquinavir), INH.

**Enz. Inducers enhance the  elimination and reduce the therapeutic efficacy.

*** Enz inhibitors decrease the elimination and increase the toxic effects.

Q29. if a patient gene has slow acetylation (hepatic N-acetyltransferase), the required dose of the isoniazid (INH) should be:

a) Increased

b) Decreased

c)Unchanged                   

d) none

Ans: b) Decreased

• Slow acetylation cause decrease the metabolism or elimination rate of INH thus required dose should be decreased, vice versa.

Q30. Phase II reactions of a drug biotransformation

(a) Decreases its water solubility

(b) Includes activity of cytochrome P-450 only

(c) Distribution into different body system

(d) Lead to inactivation of drug

 Ans: (d) Lead to inactivation of drug

Q31. Half life (t ½) doesn’t depend on:

a) Biotransformation

b) Time of drug absorption

c) Concentration of a drug in plasma

d) Rate of drug elimination

 Ans: b) Time of drug absorption

• Half Life: It is the time it takes for the plasma concentration or the amount of drug in the body to be reduced by 50% via different elimination mechanisms.

1^st order: T1/2 = 0.693/K;

K= CL/Vd

Vd= X/Pc

Q31. If the drug has excreted by First order kinetic and rate of elimination constant is 0.35 h^-1, then how much time required for eliminate 50%.

a) 2 h

b) 35 min

c) 2.8 h

d) 3 h

Ans: a) 2h

T_1/2 = 0.693/0.35 = 2 h

Q32. Which organ is involve in drug excreation

a) Kidney

b) Lungs

c) Skin

d) Saliva

e) All

Ans: e) All

Q33. Drugs are excreted by urine by EXCEPT

a) Glomerular Filtration

b) Tubular Secretion

c) Tubular reabsorption

Ans: C) Tubular reabsorption

Renal Excretion = (GF + TS) – TR

Q34. Which has higher efficiency for excretion

a) Glomerular Filteration

b) Tubular Secretion

Ans: B) Tubular Secretion

• The efficiency (performance) of the excretion by tubular secretion is higher than glomerular filtration route.
• Clearance maximum in glomerular filtration is approximately GFR: 120 ml/min, whereas the clearance maximum of tubular secretion is about TSR: 600 ml/min

Q35. Renal Clearance is affected by

a) Plasma Protein Binding

b) Tubular Secretion

c) Half life of drug

d) All

Ans: d) All

Factors that affect

• Plasma protein binding of the drug.— ——-decrease
• Tubular reabsorption ratio of the drug.——decrease
• Tubular secretion ratio of the drug. ———–increase
• Glomerular filtration ratio of the drug.——-increase
• Half life of drug— decreased