This set of Drug Biotechnology Question Paper focuses on “Physiological Barriers to Drug Distribution”.
1. Which one of the following sentences will be the actual definition of distribution?
a) Transfer of drug from the administration dosage to surrounding fluid
b) Transfer of drug from the surrounding the fluid to the blood
c) Transfer of the drug from the oral cavity to the intestine
d) Reversible transfer of drug between blood and extravascular fluids and tissues
Explanation: Distribution is the reversible transfer of a drug between the blood and the extravascular fluids and tissues. The driving force for absorption is the concentration gradient.
2. What should be the molecular weight of the drug molecules so that they can easily pass through the membrane?
a) 600-800 Dalton
b) 500-600 Dalton
c) 300-500 Dalton
d) 200-400 Dalton
Explanation: Drugs with molecular weight less than 500-600 Daltons can easily cross the capillary membrane and diffuse into the extracellular interstitial fluids. Molecular size, ionization constant, and lipophilicity controls the penetration of drugs from the extracellular fluid to the cells.
3. Which type of drug cannot enter the cell membrane in the below picture?
a) Ionized drug
b) Unionized drug
c) Hydrolyzed drug
d) Unhydrated drug
Explanation: Most drugs are weak acids or weak bases. And their degree of ionization at plasma pH depends upon their pKa. Here the drug has shown which cannot enter the cell membrane is the ionized drug.
4. Which drugs cannot pass the Capillary endothelial Barrier?
a) Molecular size less than 600 Dalton
b) Drugs bound to blood components
c) Drugs bound to a chemical moiety
d) All drugs can pass
Explanation: All drugs ionized, unionized but with a molecular size less than 600 Dalton can pass through the capillary endothelial into the interstitial fluid. Only drugs bound to the blood components are restricted because the molecular size becomes large.
5. Which of the following drug cannot pass through the plasma membrane barrier?
a) Drug size less than 50 Dalton
b) Lipophilic drugs 50-600 Dalton
c) Polar or ionized drugs of size greater than 50 Dalton
d) Drug size more than 600 Dalton
Explanation: Drugs size of fewer than 50 Daltons can only pass the plasma membrane barrier. Lipophilic drugs of molecular weight 50-600 Dalton, polarised drugs of size greater than 50deltons can also pass the given membrane.
6. Which cell make up the blood-brain barrier?
a) Squamous epithelium cells
b) Fat cells
c) Red blood cell
d) Endothelial cells
Explanation: The brain capillaries are made up of epithelial cells joined to one another by continuous tight intercellular junctions thereby making the blood-brain barrier. These are highly specialized capillaries which are much less permeable to water-soluble drugs.
7. What is the name of the specialized cells that support the blood-brain barrier tissue?
c) Fat cells
d) Endothelial cells
Explanation: Specialised cells such as astrocytes, are the supporting tissue. These are found at the base of the endothelial membrane forming a solid envelope around the brain capillaries.
8. Why dopamine cannot be administered for the disease Parkinsonism?
a) Don’t have a medicine
b) It is not the medicine
c) Cannot cross the blood-brain barrier
d) Forms aggregate and thus cannot cross the BBB
Explanation: The selective permeability of the lipid soluble moieties through the BBB does not allow several drugs to just pass the barrier. Parkinsonism cannot be treated by the administration of dopamine since dopamine cannot cross the BBB.
9. Which one of these is not an approach to make the drug cross the blood-brain barrier?
a) Using permeation enhancers
b) Osmotic disruption of the blood-brain barrier
c) Use of highly lipophilic drug only
d) Use of drug carriers to cross the BBB
Explanation: Three different approaches that have been used to promote crossing the BBB is the use of permeation enhancers such as DMSO, osmotic disruption of the BBB by infusing internal carotid artery with mannitol, Use of dihydropyridine redox system as drug carriers to the brain.
10. Which drugs can easily pass the Placental barrier?
a) Drugs having a molecular weight less than 1000 Dalton
b) Moderate to high lipid solubility
c) Drugs having a molecular weight less than 1000 Dalton and moderate to high lipid solubility, analgesics, and antibiotics
d) Analgesics, antibiotics, etc
Explanation: Drugs having a molecular weight less than 1000deltons and drugs which are moderate to high lipophilic in nature can easily pass the placental barrier. For e.g. drugs such as ethanol, anesthetics, steroids, narcotic analgesics, and antibiotics, etc. can pass the placental barrier.
11. What is the function of the blood-testis barrier?
a) Restricts the passage of drug to the testis
b) Restricts the passage of drug to sperms
c) Restricts the passage of drugs to spermatocytes
d) Restricts the passage of drugs to spermatocytes and spermatids
Explanation: Blood-testis barrier is a tight junction between Sertoli cells located at the capillary endothelial level of the testis. It acts as the blood-testes barrier restricting drugs to spermatocytes and spermatids.
12. What is the perfusion rate?
a) The total volume of blood
b) The volume of blood that flows through the heart per unit time
c) The volume of blood that flows per unit time per unit volume of tissue
d) The volume of tissue that flows per unit time per unit area of a blood vessel
Explanation: Perfusion rate is defined as the volume of blood that flows through the tissue per unit time per unit volume of the tissue. It is expressed in ml/min/ml of the tissue.
13. Placental barrier is more effective than the Blood-Brain Barrier.
Explanation: Drugs having a molecular weight less than 1000 Dalton and moderate to high lipid solubility can pass through the placental barrier. Thus, this makes the placental barrier less effective the blood-brain barrier.
14. Blood-brain barrier is a lipoidal barrier.
Explanation: Since the blood-brain barrier has a high oil-water partition coefficient. Thus, the blood-brain barrier is a lipoidal barrier. A highly lipid soluble drug can easily pass the barrier.
15. Lipophilic drugs of molecular weight range 50-600 Dalton can pass the cell membrane to reach intracellular fluid.
Explanation: Drugs of size less than 50 Dalton can pass the cell membrane to reach intracellular fluid. Lipophilic drugs 50-600 Dalton and polar or ionized drugs of size less than 50 Dalton can pass the plasma membrane barrier.
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