PHARMACOKINETICS (ADME) EXAM QUESTIONS
AND CORRECT ANSWERS (VERIFIED ANSWERS)
PLUS RATIONALES 2026
Pharmacokinetics (Absorption, Distribution, Metabolism, Excretion)
Section 1: Absorption (Questions 1–30)
1. Which of the following routes of administration has the fastest onset of action?
• A) Oral
• B) Subcutaneous
• C) Intravenous
• D) Transdermal
Answer: C
Rationale: Intravenous (IV) administration delivers drug directly into systemic
circulation, bypassing absorption barriers, achieving 100% bioavailability and
immediate onset. All other routes require absorption.
2. Bioavailability is defined as:
• A) The rate at which a drug is metabolized
• B) The fraction of an administered dose that reaches systemic circulation
unchanged
• C) The volume of distribution of a drug
• D) The time to reach peak concentration
,Answer: B
*Rationale: Bioavailability (F) is the fraction of the administered dose that reaches
systemic circulation intact. By definition, IV administration has F = 1 (100%). Oral F
is often <1 due to incomplete absorption and first-pass metabolism.*
3. A drug that undergoes extensive first-pass metabolism would have which of the
following characteristics when given orally?
• A) High oral bioavailability
• B) Low oral bioavailability
• C) Increased half-life
• D) Decreased volume of distribution
Answer: B
Rationale: First-pass metabolism (hepatic and intestinal) reduces the amount of
drug reaching systemic circulation, resulting in low oral bioavailability. Examples:
propranolol, morphine, lidocaine, nitroglycerin.
4. Which of the following factors increases the rate of drug absorption from the
small intestine?
• A) Reduced blood flow to the intestine
• B) Large particle size
• C) Lipophilicity of the drug
• D) High degree of ionization
Answer: C
Rationale: Lipophilic drugs cross cell membranes readily by passive diffusion.
Ionized drugs (D) are poorly absorbed. Increased blood flow (A) increases
absorption; large particle size (B) slows dissolution.
,5. A patient takes a weakly basic drug (pKa 8.4). In the acidic gastric fluid (pH 1.4),
the drug will be:
• A) Mostly non-ionized and well-absorbed in the stomach
• B) Mostly ionized and poorly absorbed in the stomach
• C) Mostly non-ionized but poorly absorbed due to low surface area
• D) Precipitated
Answer: B
Rationale: Weak bases are ionized (charged) at acidic pH (below their pKa). The
stomach has low surface area and the ionized form is poorly lipid-soluble, so
absorption is minimal. Most absorption occurs in the small intestine.
6. A drug that is a weak acid (pKa 4.4) will be absorbed best in which part of the
gastrointestinal tract?
• A) Stomach (pH 1.4)
• B) Duodenum (pH 5-6)
• C) Jejunum (pH 6-7)
• D) Colon (pH 7-8)
Answer: A
*Rationale: Weak acids are non-ionized (lipid-soluble) when pH < pKa. At pH 1.4
(stomach), the drug is predominantly non-ionized and can be absorbed across
gastric mucosa. However, the stomach has limited surface area.*
7. Which of the following statements about the pH partition hypothesis is correct?
• A) Weak acids are better absorbed in alkaline pH
• B) Weak bases are better absorbed in acidic pH
, • C) Weak acids are better absorbed in acidic pH
• D) Ionization has no effect on absorption
Answer: C
*Rationale: Non-ionized drugs cross membranes. Weak acids (pKa ~4-5) are non-
ionized in acid (stomach); weak bases (pKa ~7-9) are non-ionized in alkaline pH
(intestine). This is the pH partition hypothesis.*
8. A patient ingests a large overdose of a weak base drug (e.g., amphetamine).
Which of the following would reduce absorption?
• A) Administering sodium bicarbonate (alkalinizing the stomach)
• B) Administering activated charcoal
• C) Administering gastric acid (HCl)
• D) Administering a proton pump inhibitor
Answer: B
Rationale: Activated charcoal adsorbs drugs in the GI tract, reducing absorption
regardless of pH. For weak bases, acidification of stomach (C) increases ionization
(traps drug in gut), potentially reducing absorption, but activated charcoal is more
effective.
9. Sublingual administration of nitroglycerin bypasses:
• A) Renal excretion
• B) First-pass metabolism in the liver
• C) Protein binding
• D) Distribution
Answer: B
Rationale: Sublingual route absorbs drug into systemic circulation via the oral
AND CORRECT ANSWERS (VERIFIED ANSWERS)
PLUS RATIONALES 2026
Pharmacokinetics (Absorption, Distribution, Metabolism, Excretion)
Section 1: Absorption (Questions 1–30)
1. Which of the following routes of administration has the fastest onset of action?
• A) Oral
• B) Subcutaneous
• C) Intravenous
• D) Transdermal
Answer: C
Rationale: Intravenous (IV) administration delivers drug directly into systemic
circulation, bypassing absorption barriers, achieving 100% bioavailability and
immediate onset. All other routes require absorption.
2. Bioavailability is defined as:
• A) The rate at which a drug is metabolized
• B) The fraction of an administered dose that reaches systemic circulation
unchanged
• C) The volume of distribution of a drug
• D) The time to reach peak concentration
,Answer: B
*Rationale: Bioavailability (F) is the fraction of the administered dose that reaches
systemic circulation intact. By definition, IV administration has F = 1 (100%). Oral F
is often <1 due to incomplete absorption and first-pass metabolism.*
3. A drug that undergoes extensive first-pass metabolism would have which of the
following characteristics when given orally?
• A) High oral bioavailability
• B) Low oral bioavailability
• C) Increased half-life
• D) Decreased volume of distribution
Answer: B
Rationale: First-pass metabolism (hepatic and intestinal) reduces the amount of
drug reaching systemic circulation, resulting in low oral bioavailability. Examples:
propranolol, morphine, lidocaine, nitroglycerin.
4. Which of the following factors increases the rate of drug absorption from the
small intestine?
• A) Reduced blood flow to the intestine
• B) Large particle size
• C) Lipophilicity of the drug
• D) High degree of ionization
Answer: C
Rationale: Lipophilic drugs cross cell membranes readily by passive diffusion.
Ionized drugs (D) are poorly absorbed. Increased blood flow (A) increases
absorption; large particle size (B) slows dissolution.
,5. A patient takes a weakly basic drug (pKa 8.4). In the acidic gastric fluid (pH 1.4),
the drug will be:
• A) Mostly non-ionized and well-absorbed in the stomach
• B) Mostly ionized and poorly absorbed in the stomach
• C) Mostly non-ionized but poorly absorbed due to low surface area
• D) Precipitated
Answer: B
Rationale: Weak bases are ionized (charged) at acidic pH (below their pKa). The
stomach has low surface area and the ionized form is poorly lipid-soluble, so
absorption is minimal. Most absorption occurs in the small intestine.
6. A drug that is a weak acid (pKa 4.4) will be absorbed best in which part of the
gastrointestinal tract?
• A) Stomach (pH 1.4)
• B) Duodenum (pH 5-6)
• C) Jejunum (pH 6-7)
• D) Colon (pH 7-8)
Answer: A
*Rationale: Weak acids are non-ionized (lipid-soluble) when pH < pKa. At pH 1.4
(stomach), the drug is predominantly non-ionized and can be absorbed across
gastric mucosa. However, the stomach has limited surface area.*
7. Which of the following statements about the pH partition hypothesis is correct?
• A) Weak acids are better absorbed in alkaline pH
• B) Weak bases are better absorbed in acidic pH
, • C) Weak acids are better absorbed in acidic pH
• D) Ionization has no effect on absorption
Answer: C
*Rationale: Non-ionized drugs cross membranes. Weak acids (pKa ~4-5) are non-
ionized in acid (stomach); weak bases (pKa ~7-9) are non-ionized in alkaline pH
(intestine). This is the pH partition hypothesis.*
8. A patient ingests a large overdose of a weak base drug (e.g., amphetamine).
Which of the following would reduce absorption?
• A) Administering sodium bicarbonate (alkalinizing the stomach)
• B) Administering activated charcoal
• C) Administering gastric acid (HCl)
• D) Administering a proton pump inhibitor
Answer: B
Rationale: Activated charcoal adsorbs drugs in the GI tract, reducing absorption
regardless of pH. For weak bases, acidification of stomach (C) increases ionization
(traps drug in gut), potentially reducing absorption, but activated charcoal is more
effective.
9. Sublingual administration of nitroglycerin bypasses:
• A) Renal excretion
• B) First-pass metabolism in the liver
• C) Protein binding
• D) Distribution
Answer: B
Rationale: Sublingual route absorbs drug into systemic circulation via the oral
