B.Pharmacy 6th Semester Biopharmaceutics & Pharmacokinetics Important Question Answer
B.Pharma VI Semester Biopharmaceutics & Pharmacokinetics Important Question Answer
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Biopharmaceutics & Pharmacokinetics Very Short Answer Question [2 Marks]
1. Define bioavailability and explain various types of bioavailability.
Ans: Bioavailability is the rate and extent to which an active drug ingredient is absorbed and becomes available at the site of action.
Types:
Absolute bioavailability compares to IV route.
Relative bioavailability compares two non-IV formulations.
2. Enumerate various advantages of sustained release dosage form.
Ans:
Maintains steady plasma drug concentration
Reduces dosing frequency
Minimizes side effects
Improves patient compliance
Reduces fluctuation between peak and trough levels
3. Write in brief about different types of dissolution apparatus.
Ans:
USP Apparatus I (Basket type): Rotating basket; suitable for capsules.
USP Apparatus II (Paddle type): Rotating paddle; ideal for tablets.
USP Apparatus III (Reciprocating cylinder): For modified-release dosage forms.
USP Apparatus IV (Flow-through cell): Best for poorly soluble drugs.
4. Define drug absorption and enlist various factors affecting drug absorption.
Ans:
Drug absorption is the process by which a drug moves from its site of administration into systemic circulation.
Factors:
Physicochemical properties of drug
Formulation factors
Gastric emptying rate
Blood flow to absorption site
Surface area
5. What is renal clearance?
Ans:
Renal clearance is the volume of plasma completely cleared of a drug by the kidneys per unit time.
Formula:
Clr=Urine concentration×Urine flow ratePlasma concentrationCl_r = \frac{Urine\ concentration \times Urine\ flow\ rate}{Plasma\ concentration}Clr =Plasma concentrationUrine concentration×Urine flow rate
6. Define passive diffusion.
Ans:
Passive diffusion is the movement of drug molecules from a region of high concentration to low concentration across a biological membrane without energy or carrier involvement.
7. What is facilitated diffusion?
Ans:
Facilitated diffusion is the transport of drugs across cell membranes using specific carrier proteins, down the concentration gradient, without energy expenditure.
8. Define active transport and give an example.
Ans:
Active transport is the movement of drug molecules against the concentration gradient using carrier proteins and energy (ATP).
Example: Absorption of levodopa via amino acid transporters.
9. What is meant by pinocytosis?
Ans:
Pinocytosis is a type of endocytosis where the cell engulfs extracellular fluid and its contents into small vesicles, enabling drug entry into cells.
10. Define endocytosis.
Ans:
Endocytosis is the cellular process in which substances are engulfed by the cell membrane to form vesicles and transported into the cell.
11. Write the name of physiological barrier affecting distribution of drug.
Ans:
Blood-brain barrier (BBB) is the main physiological barrier that restricts drug distribution into the brain and central nervous system.
12. Define Biopharmaceutics.
Ans:
Biopharmaceutics is the study of how the physicochemical properties of drugs, dosage forms, and routes of administration affect the rate and extent of drug absorption.
13. Define Renal clearance.
Ans:
Renal clearance is the volume of plasma cleared of a drug by the kidneys per unit time, indicating the efficiency of renal drug elimination.
14. Explain term In Vitro-In Vivo correlation.
Ans:
IVIVC is a predictive mathematical model describing the relationship between an in vitro drug release and its in vivo bioavailability or pharmacokinetic profile.
15. Define Km & Vmax.
Ans:
Km (Michaelis constant): Drug concentration at which the rate of reaction is half of Vmax.
Vmax: Maximum rate of drug metabolism when enzymes are saturated.
16. Define tissue permeability of drugs.
Ans:
Tissue permeability refers to the ability of a drug to pass through biological membranes and enter tissues. It depends on lipid solubility, molecular size, and ionization of the drug.
17. Explain Bioequivalence.
Ans:
Bioequivalence means that two drug products have similar bioavailability and produce the same effect at the site of action when given in the same dose under similar conditions.
18. Write the name of factors causing Non-linearity.
Ans:
Saturation of metabolism (enzyme capacity)
Saturable protein binding
Active transport saturation
Changes in renal clearance
Dose-dependent absorption or elimination
19. Define two compartment model.
Ans:
In the two-compartment model, the body is divided into central and peripheral compartments. Drug distributes quickly in the central and more slowly into the peripheral compartment.
20. Define absolute and relative bioavailability.
Ans:
Absolute bioavailability: Comparison of drug availability from a non-IV route to IV route.
Relative bioavailability: Comparison of two different non-IV formulations.
21. Describe Noyes Whitney equation.
Ans:
The Noyes-Whitney equation describes the rate of drug dissolution:
dCdt=DA(Cs−C)h\frac{dC}{dt} = \frac{DA (C_s - C)}{h}dtdC =hDA(Cs −C)
Where D = diffusion coefficient, A = surface area, Cs = solubility, C = concentration, h = thickness of boundary layer.
22. Describe Henderson Hasselbalch equation.
Ans:
pH=pKa+log([A−][HA])pH = pKa + \log\left(\frac{[A^-]}{[HA]}\right)pH=pKa+log([HA][A−] )
It relates pH, pKa, and ratio of ionized to unionized drug forms. It helps predict drug absorption depending on ionization.
23. Describe Michaelis-Menten equation.
Ans:
v=Vmax[S]Km+[S]v = \frac{V_{max}[S]}{K_m + [S]}v=Km +[S]Vmax [S]
Describes the rate of enzyme-catalyzed reactions. Vmax is the maximum rate, Km is substrate concentration at half Vmax.
24. Differentiate between absorption and permeation.
Ans:
Absorption: Entry of drug into bloodstream from the site of administration.
Permeation: Movement of drug across cell membranes or barriers.
25. Define active transport of drugs.
Ans:
Active transport involves energy-dependent carrier-mediated movement of drugs across membranes, often against a concentration gradient.
26. Draw a one compartment model, oral route.
Ans:
(A labeled diagram showing: Drug in GIT → Absorption rate constant (Ka) → Central compartment → Elimination rate constant (Ke))
📌 I can draw the diagram if needed—let me know!
27. Draw a two compartment model, I.V. bolus.
Ans:
(A labeled diagram showing: Central compartment ↔ Peripheral compartment; drug eliminated from central)
📌 Let me know if you want an actual image.
28. Draw a multiple dosage regimen curve for oral route.
Ans:
(Graph: Time vs Plasma concentration showing accumulation of drug with repeated doses, reaching steady state)
📌 I can generate this graph on request.
29. Name any four pharmaceutical factors influencing drug absorption through GIT.
Ans:
Dosage form design
Disintegration rate
Dissolution rate
Use of excipients
30. Name any four physico-chemical factors influencing drug absorption through GIT.
Ans:
Solubility
Lipid-water partition coefficient
Molecular size
Degree of ionization
31. Define biopharmaceutics.
Ans:
Biopharmaceutics is the study of the relationship between the physicochemical properties of a drug, its dosage form, and the biological effects observed after administration.
32. Name the pharmacokinetic parameters in which parameters of drug will change with change in dose.
Ans:
Volume of distribution (Vd)
Clearance (Cl)
Half-life (t½)
Area under curve (AUC)
Maximum concentration (Cmax)
33. What is diffusion?
Ans:
Diffusion is the passive movement of drug molecules from an area of higher concentration to an area of lower concentration, across a membrane or within a solution.
34. Name any two physiological factors influencing drug absorption through GIT.
Ans:
Gastric emptying time
Intestinal blood flow
35. What is first pass effect?
Ans:
First pass effect is the metabolism of a drug in the liver or gut wall during its first passage from the GIT to systemic circulation, reducing bioavailability.
36. Define tissue permeability.
Ans:
Tissue permeability refers to the ability of a drug to cross cell membranes and distribute into tissues, influenced by lipophilicity and molecular size.
37. Define dosage regimen.
Ans:
A dosage regimen is the schedule of drug administration, including the dose, frequency, and duration, intended to maintain effective drug levels in the body.
38. What do you mean by enteropathic circulation?
Ans:
Enterohepatic circulation refers to the recycling of drugs or metabolites from the liver to the bile, into the intestine, and back into systemic circulation.
39. Differentiate between first order and zero order kinetics.
Ans:
First-order: Rate depends on drug concentration; constant fraction eliminated.
Zero-order: Rate is constant; fixed amount eliminated regardless of concentration.
40. Define the term IVIVC.
Ans:
In Vitro-In Vivo Correlation (IVIVC) is the relationship between a drug’s in vitro release characteristics and its in vivo absorption or bioavailability profile.
41. Define drug absorption.
Ans:
Drug absorption is the process by which a drug moves from its site of administration into the bloodstream, influenced by formulation and physiological factors.
42. Define blood-brain barrier.
Ans:
The blood-brain barrier (BBB) is a selective physiological barrier that restricts the entry of most drugs into the brain to protect the central nervous system.
43. Define sink condition.
Ans:
Sink condition exists when the concentration of drug in the dissolution medium is much lower than its saturation solubility, allowing constant dissolution rate.
44. Define the term bioavailable fraction (F).
Ans:
Bioavailable fraction (F) is the portion of an administered drug dose that reaches the systemic circulation in an unchanged form.
45. Define apparent volume of distribution.
Ans:
Apparent volume of distribution (Vd) is a theoretical volume that relates the amount of drug in the body to the concentration of drug in the plasma.
Vd=Amount of drugPlasma concentrationV_d = \frac{Amount\ of\ drug}{Plasma\ concentration}Vd =Plasma concentrationAmount of drug
46. Define area under curve (AUC).
Ans:
AUC is the integral of the plasma drug concentration-time curve; it represents the total drug exposure over time and is used to assess bioavailability.
47. Define zero order kinetics.
Ans:
Zero-order kinetics describes drug elimination at a constant rate, independent of the drug’s concentration. Example: Phenytoin at high doses.
48. Define dose dependent kinetics.
Ans:
Dose-dependent kinetics occur when pharmacokinetic parameters such as clearance or bioavailability change with the administered dose due to saturation processes.
49. What is enterohepatic circulation?
Ans:
Enterohepatic circulation is the recycling process where drugs/metabolites excreted in bile are reabsorbed from the intestine into the systemic circulation.
50. Define the term BCS classification.
Ans:
The Biopharmaceutics Classification System (BCS) classifies drugs into four categories based on solubility and intestinal permeability, aiding in regulatory decisions.
51. Define Physiological model.
Ans:
A physiological pharmacokinetic model uses actual anatomical and physiological parameters of organs and tissues to describe drug distribution and elimination.
52. In compartmental modeling what does the term "apparent" mean?
Ans:
"Apparent" indicates that the value (e.g., volume of distribution) is a mathematical construct and may not reflect a real anatomical volume or structure.
53. Define absolute effective concentration and maximum safe concentration.
Ans:
Absolute effective concentration: Minimum drug concentration needed for therapeutic effect.
Maximum safe concentration: Highest concentration without producing toxic effects.
54. Define minimum toxic dose.
Ans:
Minimum toxic dose is the smallest dose of a drug that produces harmful or toxic effects in a patient or subject.
55. Define the difference between first-order and zero-order process.
Ans:
First-order: Elimination rate ∝ drug concentration.
Zero-order: Elimination rate is constant, independent of concentration.
56. Define loading dose and dilution with water.
Ans:
Loading dose: An initial high dose to quickly achieve therapeutic concentration.
Dilution with water: Process of reducing drug concentration by adding water.
57. Define various models in drug distribution.
Ans:
Compartment models (one, two)
Non-compartmental model
Physiological model (PBPK)
Each model describes how drug distributes and is eliminated in the body.
58. Define perfusion rate-limited model.
Ans:
This model assumes that drug distribution into tissue is limited by blood flow (perfusion), not by membrane permeability.
59. Define partition coefficient.
Ans:
Partition coefficient (P) is the ratio of drug concentration in oil (lipid) to water; it indicates lipophilicity and affects membrane permeability.
60. Define therapeutic index and therapeutic range.
Ans:
Therapeutic index (TI): Ratio of toxic dose to effective dose.
Therapeutic range: Plasma drug concentration range that provides efficacy without toxicity.
61. Define absorption.
Ans:
Absorption is the process by which a drug moves from the site of administration into the systemic circulation for therapeutic effect.
62. Classify routes of drug administration.
Ans:
Enteral: Oral, sublingual, rectal
Parenteral: IV, IM, SC
Topical: Dermal, ophthalmic
Inhalation: Pulmonary route
63. Define bioavailability of drug excretion.
Ans:
This term is uncommon. Possibly a misinterpretation. Correct:
Bioavailability is the fraction of drug reaching systemic circulation.
Excretion refers to elimination via urine, feces, etc.
64. Describe the concept of apparent volume of distribution.
Ans:
Apparent volume of distribution (Vd) is the volume in which a drug would need to be uniformly distributed to give the observed plasma concentration. It indicates the extent of drug distribution in body tissues.
65. Define loading dose.
Ans:
Loading dose is an initial higher dose of a drug given to rapidly achieve a therapeutic plasma concentration.
Loading Dose=Vd×CtargetFLoading\ Dose = \frac{V_d \times C_{target}}{F}Loading Dose=FVd ×Ctarget
66. Define non-linear pharmacokinetics.
Ans:
Non-linear pharmacokinetics occur when the rate of drug absorption, distribution, or elimination changes with dose due to saturation of processes like enzymes or transporters.
67. Define half-life.
Ans:
Half-life (t½) is the time required for the plasma concentration of a drug to reduce by 50%.
t1/2=0.693×VdClt_{1/2} = \frac{0.693 \times V_d}{Cl}t1/2 =Cl0.693×Vd
68. Define Gastric Emptying Time and its significance.
Ans:
Gastric emptying time is the time taken for stomach contents to move into the small intestine. It affects the onset, rate, and extent of drug absorption.
69. Define Ka.
Ans:
Ka is the absorption rate constant, representing the rate at which a drug enters systemic circulation from the site of administration.
70. Write formula for area under curve (AUC).
Ans:
For IV bolus:
AUC=DoseClearanceAUC = \frac{Dose}{Clearance} AUC=ClearanceDose
For oral dose:
AUC=F×DoseClAUC = \frac{F \times Dose}{Cl}AUC=ClF×Dose
B.Pharmacy 6th Semester All Subject Important Short Question Answer
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