APhA NAPLEX Review Questions
If the pka of a weak acid is 2.5, at which pH will this drug become more ionized?
A. pH 5
B. pH 2.5
C. pH 1.5
D. pH 1 - ANS A. For a weak acid, a higher pH increases ionization
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 - ANS 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
Michaelis-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 Michaelis-Menten equation
D. Young's equation - ANS 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
dissociation 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 - ANS B. When the pH = pka, the ratio of ionized to unionized 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 - ANS 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 - ANS 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 - ANS 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 proportional 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 - ANS 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 - ANS 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
Which of the following statements about lyophilic colloidal dispersions is true?
A. They tend to be more sensitive to the addition of electrolytes than do lyophobic systems
B. They tend to be more viscous than lyophobic systems
C. They can be precipitated by prolonged dialysis
D. They separate rapidly - ANS B. Most lyophilic colloids are organic molecules (including
gelatin and acacia); they spontaneously form colloidal solutions and tend to be viscous.
Dispersion of lyophilic colloids is stable in the presence of electrolytes
Which of the following is not true for tablet formulations?
A. A disintegrating agent promotes granule flow
B. Lubricants prevent adherence of granules to the punch faces of the tableting machine
C. Glidants promote flow of the granules
D. Binding agents are used for adhesion of powder into granules - ANS A. Disintegrating
agents are added to the tablets to promote breakup of the tablets when placed in the aqueous
environment. Lubricants are required to prevent adherence of the granules to the punch faces
and dies. Glidants are added to tablet formulations to improve the flow properties of the
granulations. Binding agents are added to bind powders together in the granulation process
The absorption rate of a drug is most rapid when the drug is formulated as
A. a controlled-release product
B. a hard gelatin capsule
C. a compressed tablet
D. a solution - ANS D. For a drug in solution, no dissolution is required before absorption.
Consequently, compared with other drug formulations, a drug in aqueous solution has the
highest bioavailability rate and is often used as the reference preparation for other formulations
According to the Noyes-Whitney equation, the drug concentration immediately at the solid
surface within the diffusion layer (stagnant layer) is recognized as the
A. drug solubility
B. dissolution rate
C. thickness layer
D. diffusion coefficient - ANS A. According to the Noyes-Whitney equation, the drug
concentration in the stagnant layer is equal to the drug solubility
Adding PEG groups to large molecules will enhance their
If the pka of a weak acid is 2.5, at which pH will this drug become more ionized?
A. pH 5
B. pH 2.5
C. pH 1.5
D. pH 1 - ANS A. For a weak acid, a higher pH increases ionization
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 - ANS 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
Michaelis-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 Michaelis-Menten equation
D. Young's equation - ANS 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
dissociation 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 - ANS B. When the pH = pka, the ratio of ionized to unionized 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 - ANS 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 - ANS 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 - ANS 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 proportional 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 - ANS 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 - ANS 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
Which of the following statements about lyophilic colloidal dispersions is true?
A. They tend to be more sensitive to the addition of electrolytes than do lyophobic systems
B. They tend to be more viscous than lyophobic systems
C. They can be precipitated by prolonged dialysis
D. They separate rapidly - ANS B. Most lyophilic colloids are organic molecules (including
gelatin and acacia); they spontaneously form colloidal solutions and tend to be viscous.
Dispersion of lyophilic colloids is stable in the presence of electrolytes
Which of the following is not true for tablet formulations?
A. A disintegrating agent promotes granule flow
B. Lubricants prevent adherence of granules to the punch faces of the tableting machine
C. Glidants promote flow of the granules
D. Binding agents are used for adhesion of powder into granules - ANS A. Disintegrating
agents are added to the tablets to promote breakup of the tablets when placed in the aqueous
environment. Lubricants are required to prevent adherence of the granules to the punch faces
and dies. Glidants are added to tablet formulations to improve the flow properties of the
granulations. Binding agents are added to bind powders together in the granulation process
The absorption rate of a drug is most rapid when the drug is formulated as
A. a controlled-release product
B. a hard gelatin capsule
C. a compressed tablet
D. a solution - ANS D. For a drug in solution, no dissolution is required before absorption.
Consequently, compared with other drug formulations, a drug in aqueous solution has the
highest bioavailability rate and is often used as the reference preparation for other formulations
According to the Noyes-Whitney equation, the drug concentration immediately at the solid
surface within the diffusion layer (stagnant layer) is recognized as the
A. drug solubility
B. dissolution rate
C. thickness layer
D. diffusion coefficient - ANS A. According to the Noyes-Whitney equation, the drug
concentration in the stagnant layer is equal to the drug solubility
Adding PEG groups to large molecules will enhance their
