APHA NAPLEX ACTUAL EXAM PAPER
2026 QUESTIONS WITH SOLUTIONS
GRADED A+
●● Which equation describes the rate of drug dissolution from a tablet?
A. Fick's Law
B. Henderson-Hasselbalch equation
C. Michaelis-Menten equation
D. Noyes-Whitney equation. Answer: D. The Noyes-Whitney equation
describes the rate of drug dissolution from a tablet. Fick's first law of
diffusion is similar to the Noyes-Whitney equation in that both equations
describe drug movement attributable to a concentration gradient. The
Michealis-Menten equation involves enzyme kinetics, whereas
Henderson-Hasselbalch equations are used for determination of pH of
the buffer and the extent of ionization of a drug molecule
●● The pH of a buffer system can be calculated with
A. the Henderson-Hasselbalch equation
B. the Noyes-Whitney equation
C. the Michealis-Mention equation
,D. Yong's equation. Answer: A. The Henderson-Hasselbalch equation
form a weak acid and its salt is represented as pH = pka + log
([salt]/[acid]), where pka is the negative log of the dissolution constant
of a weak acid, as [salt]/[acid] is the ratio of the molar concentration of
salt and acid used to prepare a buffer
●● If the pka of a drug is 5, at which of the following pH values do the
ionic and nonionic forms of the drug exist at equal ratio?
A. pH 1
B. pH 5
C. pH 7
D. pH 9. Answer: B. When the pH = pka, the ratio of ionized to un-
ionized becomes the same
●● What is bioavailability?
A. Bioavailability is the measurement of the rate and extent of active
drug that reaches the systemic circulation
B. It is the relationship between the physical and chemical properties of
a drug and its systemic absorption
C. It is the movement of the drug into body tissues over time
D. It is the dissolution of the drug in the GI tract. Answer: A.
Bioavailability is the measurement of the rate and extent of systemic
circulation of an active drug
,●● Which of the following may be used to assess the relative
bioavailability of two chemically equivalent drug products in a crossover
study?
A. Dissolution test
B. Peak concentration
C. Time-to-peak concentration
D. Area under the plasma-level time curve. Answer: D. The plasma drug
concentration versus time curve measures the bioavailability of a drug
from a product. The peak plasma drug concentration (Cmax) relates to
the intensity of the pharmacologic response, while the time for peak
plasma drug concentration (Tmax) relates to the rate of systemic
absorption
●● What condition usually increases the rate of drug dissolution for a
tablet?
A. Increase the particle size of the drug
B. Decrease the surface area of the drug
C. Use of ionized, or salt, form of the drug
D. Use of the free acid or free base form of the drug. Answer: C. The
ionized, or salt, form of a drug is generally more water soluble and
therefore dissolves more rapidly than the nonionized (free acid or free
base) form of the drug. According to the Noyes-Whitney equation, the
, dissolution rate is directly proportion to the surface area and inversely
proportional to the particle size. Therefore, an increase in the particle
size or a decrease in the surface area slows the dissolution rate
●● If the pka of a weak base drug is 8.3, at which of the following pH
values does this drug become more ionized?
A. pH 4
B. pH 9
C. pH 10
D. pH 13. Answer: A. For a weak base, a lower pH value increase
ionization of the molecule
●● Which of the following dosage forms may use surface-active agents
in their formulations?
A. Emulsions
B. Suspensions
C. Colloidal dosage forms
D. Creams
E. All of the Above. Answer: E. Surface active agents facilitate emulsion
formation by lowering the interfacial tension between the oil and water
phases. Adsorption of surfactants on insoluble particles enables these
particles to be dispersed in the form of a suspension
2026 QUESTIONS WITH SOLUTIONS
GRADED A+
●● Which equation describes the rate of drug dissolution from a tablet?
A. Fick's Law
B. Henderson-Hasselbalch equation
C. Michaelis-Menten equation
D. Noyes-Whitney equation. Answer: D. The Noyes-Whitney equation
describes the rate of drug dissolution from a tablet. Fick's first law of
diffusion is similar to the Noyes-Whitney equation in that both equations
describe drug movement attributable to a concentration gradient. The
Michealis-Menten equation involves enzyme kinetics, whereas
Henderson-Hasselbalch equations are used for determination of pH of
the buffer and the extent of ionization of a drug molecule
●● The pH of a buffer system can be calculated with
A. the Henderson-Hasselbalch equation
B. the Noyes-Whitney equation
C. the Michealis-Mention equation
,D. Yong's equation. Answer: A. The Henderson-Hasselbalch equation
form a weak acid and its salt is represented as pH = pka + log
([salt]/[acid]), where pka is the negative log of the dissolution constant
of a weak acid, as [salt]/[acid] is the ratio of the molar concentration of
salt and acid used to prepare a buffer
●● If the pka of a drug is 5, at which of the following pH values do the
ionic and nonionic forms of the drug exist at equal ratio?
A. pH 1
B. pH 5
C. pH 7
D. pH 9. Answer: B. When the pH = pka, the ratio of ionized to un-
ionized becomes the same
●● What is bioavailability?
A. Bioavailability is the measurement of the rate and extent of active
drug that reaches the systemic circulation
B. It is the relationship between the physical and chemical properties of
a drug and its systemic absorption
C. It is the movement of the drug into body tissues over time
D. It is the dissolution of the drug in the GI tract. Answer: A.
Bioavailability is the measurement of the rate and extent of systemic
circulation of an active drug
,●● Which of the following may be used to assess the relative
bioavailability of two chemically equivalent drug products in a crossover
study?
A. Dissolution test
B. Peak concentration
C. Time-to-peak concentration
D. Area under the plasma-level time curve. Answer: D. The plasma drug
concentration versus time curve measures the bioavailability of a drug
from a product. The peak plasma drug concentration (Cmax) relates to
the intensity of the pharmacologic response, while the time for peak
plasma drug concentration (Tmax) relates to the rate of systemic
absorption
●● What condition usually increases the rate of drug dissolution for a
tablet?
A. Increase the particle size of the drug
B. Decrease the surface area of the drug
C. Use of ionized, or salt, form of the drug
D. Use of the free acid or free base form of the drug. Answer: C. The
ionized, or salt, form of a drug is generally more water soluble and
therefore dissolves more rapidly than the nonionized (free acid or free
base) form of the drug. According to the Noyes-Whitney equation, the
, dissolution rate is directly proportion to the surface area and inversely
proportional to the particle size. Therefore, an increase in the particle
size or a decrease in the surface area slows the dissolution rate
●● If the pka of a weak base drug is 8.3, at which of the following pH
values does this drug become more ionized?
A. pH 4
B. pH 9
C. pH 10
D. pH 13. Answer: A. For a weak base, a lower pH value increase
ionization of the molecule
●● Which of the following dosage forms may use surface-active agents
in their formulations?
A. Emulsions
B. Suspensions
C. Colloidal dosage forms
D. Creams
E. All of the Above. Answer: E. Surface active agents facilitate emulsion
formation by lowering the interfacial tension between the oil and water
phases. Adsorption of surfactants on insoluble particles enables these
particles to be dispersed in the form of a suspension
