Drug Biotechnology Multiple Choice Questions on “Bioavailability – Measurement”.
1. What is bioavailability?
a) The time of absorption of the drug from its dosage form
b) The rate of absorption of the unchanged drug from its dosage form
c) The time of absorption of the unchanged drug from its dosage form
d) The rate of absorption of the drug from its dosage form
Answer: b
Clarification: Physiologic availability, biologic availability or just bioavailability is defined as the rate or the amount of absorption of an unchanged drug from its dosage form. The rate with which the drug is getting absorbed is important since in some treatment such as asthma attack rapid onset action is required.
2. What is the equation of bioavailable fraction?
a) 1/Bioavailable dose
b) 1/Administered dose
c) Bioavailable dose/Administered dose
d) Administered dose/Bioavailable dose
Answer: c
Clarification: The amount of drug that reaches the systemic circulation is known as systemic bioavailability. The bioavailable fraction F refers to the fraction of administered dose that enters the systemic circulation after drug administration. The equation is F = Bioavailable dose/Administered dose.
3. Which of the following is not an objective of bioavailability studies?
a) Primary stages of development of suitable dosage form for new drug
b) Determination of the influence of excipients, patient-related factors, etc
c) Development of new formulations of the existing drugs
d) Control the quantity of the drug to be administered
Answer: d
Clarification: More than the quantity, bioavailability studies are more used to study the quality of a drug product during the early stages of marketing so that the influence of processing factors, storage, and stability on drug absorption can be determined. Other objectives are the development of suitable dosage form, determination of the influence of excipients, patient-related factors, etc. and development of new formulations of the existing drugs.
4. Single-dose bioavailability studies are simple and common.
a) True
b) False
Answer: a
Clarification: Single-dose bioavailability studies are common, easy, offer less exposure to drugs and are less tedious. Although it is difficult in a single dose bioavailability study to predict the steady-state characteristics of a drug and inter-subject variability. Multiple dose study is difficult to control.
5. Multiple dose study is better since we can understand the peak, valley, drug blood levels, etc.
a) True
b) False
Answer: a
Clarification: Multiple dose study is difficult to control since it exposes the subject to a higher level of drug which is dangerous sometimes. This method is very tedious and time-consuming. The advantages of such method are accurately reflected how the drug should be used, easy to predict peak and valley of a drug, can be ethically performed on the patient, better evaluation of the performance of controlled release formulation is possible.
6. Which of the following is the pharmacodynamics method of studying bioavailability?
a) Acute pharmacologic response
b) Plasma-level time studies
c) Urinary excretion studies
d) Stool excretion studies
Answer: a
Clarification: Pharmacodynamic methods are a direct measurement of the drug effect on physiological processes as a function of time. The methods are acute pharmacologic response and therapeutic response. Pharmacokinetics method is indirect methods and these are Plasma level time studies and Urinary excretion studies.
7. Which of the following is not an important parameter of plasma level time studies?
a) Cmax
b) Tax
c) The area under the plasma level-time curve
d) Steady state level
Answer: d
Clarification: Cmax is the peak plasma concentration which shows whether the drug is being absorbed systemically so that it can be able to provide a therapeutic response. Tmax is the peak time which will give the indication of the rate of absorption. The area under the plasma level-time curve gives the measure of the quantity of absorption of the drug that reaches the systemic circulation.
8. What is the equation for bioavailability?
a) [AUC]std Dstd τtest / [AUC]test Dtest τstd
b) [AUC]test Dtest τstd / [AUC]std Dstd τtest
c) [AUC]test Dstd τtest / [AUC]std Dtest τstd
d) 1 / [AUC]std Dtest τstd
Answer: c
Clarification: The equation of bioavailability is [AUC]test Dstd τtest / [AUC]std Dtest τstd, D stands for dose administered, test and std indicate the test and standard doses of the same drug to determine the relative availability. The dosing interval is τ.
9. The urinary excretion of the unchanged drug is directly proportional to the plasma concentration of a drug.
a) True
b) False
Answer: a
Clarification: Urinary excretion studies help in assessing bioavailability is based on the principle that urinary excretion of unchanged drug is directly proportional to the plasma concentration of a drug. If a drug is excreted at least 10 to 20% in the urine, bioavailability can be determined.
10. Which of the following will not be a parameter that should be examined for urinary excretion data?
a) (dXu/dt)max
b) (tu)max
c) Xu
d) Cmax
Answer: d
Clarification: (dXu/dt)max is the maximum urinary excretion rate. It is analogous to Cmax from plasma level studies since the rate of appearance of drug in the urine is proportional to its concentration in circulation. Its value increases as the rate of absorption increases. (tu)max is the time for maximum excretion rate, its value decreases as the absorption rate increases. Xu is the cumulative amount of drug excreted in the urine.
11. Find out the correct option for the marked place in the given picture of the rate of excretion versus midpoint time of urine collection period curve.
a) (dXu/dt)max
b) (tu)max
c) Xu
d) Cmax
Answer: a
Clarification: (dXu/dt)max is the maximum urinary excretion rate. This is obtained from the peak of the rate of excretion versus midpoint time of urine collection period. It is analogous to Cmax from plasma level studies since the rate of appearance of drug in the urine is proportional to its concentration in circulation. Its value increases as the rate of absorption increases. (tu)max is the time for maximum excretion rate, its value decreases as the absorption rate increases. Xu is the cumulative amount of drug excreted in the urine.
12. Find out the correct option for the marked place in the given picture of the rate of excretion versus midpoint time of urine collection period curve.
a) (dXu/dt)max
b) (tu)max
c) Xu
d) Cmax
Answer: b
Clarification: (dXu/dt)max is the maximum urinary excretion rate. This is obtained from the peak of the rate of excretion versus midpoint time of urine collection period. (tu)max is the time for maximum excretion rate, its value decreases as the absorption rate increases. The curve is analogous to plasma-level time profile obtained after oral administration of a single dose of the drug.
13. Which of the following is not measured in acute pharmacological response study?
a) ECG
b) EEG
c) Pupil diameter
d) Serum drug level
Answer: d
Clarification: When bioavailability measurement using pharmacokinetic processes are difficult, inaccurate, non-reproducible, acute pharmacological effect such as a change in ECG, EEG, pupil diameter, etc. is related to the time course of a given drug. Bioavailability can then be calculated by construction the pharmacologic effect-time curve as well as dose-response graphs.
14. Therapeutic response is based on observing the clinical response to a drug formulation.
a) True
b) False
Answer: a
Clarification: Therapeutic response is based upon the clinical responses to a drug formulation given to patients suffering from the disease for which the drug should be used. A drawback of the method is the quantification of observed response is not proper to allow for assessment of relative bioavailability between dosage forms of the same drug.
15. In vitro determination of bioavailability by dissolution rate is not the best way to determine therapeutic efficacy.
a) True
b) False
Answer: b
Clarification: Physicochemical property of most of the drugs that have the greatest influence on their absorption characteristics from the gastrointestinal tract is dissolution rate. To assess the therapeutic efficacy of slow dissolving drugs is in vivo determination of bioavailability. It is done whenever a new formulation is to be introduced in the market.