PSI Pharmaceutical Sciences 1 — Questions and Answers
Question 1: Which route of administration provides 100% bioavailability?
- Intravenous (Correct answer)
- Oral
- Intramuscular
- Subcutaneous
Correct answer: Intravenous
Intravenous administration delivers drug directly into systemic circulation, bypassing first-pass metabolism and absorption barriers, giving 100% bioavailability.
Question 2: What is the Henderson-Hasselbalch equation used to calculate?
- pH of a buffer solution (Correct answer)
- Osmolarity of a solution
- Partition coefficient
- Solubility product
Correct answer: pH of a buffer solution
The Henderson-Hasselbalch equation (pH = pKa + log [A-]/[HA]) calculates the pH of a buffer based on the ratio of conjugate base to weak acid.
Question 3: Which process describes drug movement from high to low concentration without energy expenditure?
- Passive diffusion (Correct answer)
- Active transport
- Endocytosis
- Facilitated transport
Correct answer: Passive diffusion
Passive diffusion moves drug molecules down a concentration gradient without requiring energy (ATP). It is the most common absorption mechanism.
Question 4: The volume of distribution (Vd) of a highly lipophilic drug is typically:
- Large, as drug distributes into tissues (Correct answer)
- Small, as drug stays in plasma
- Equal to total body water
- Equal to plasma volume
Correct answer: Large, as drug distributes into tissues
Lipophilic drugs partition extensively into fatty tissues and plasma proteins, resulting in a large apparent volume of distribution well above actual body fluid volumes.
Question 5: Which excipient acts as a disintegrant in tablet formulations?
- Croscarmellose sodium (Correct answer)
- Magnesium stearate
- Lactose monohydrate
- Povidone
Correct answer: Croscarmellose sodium
Croscarmellose sodium is a superdisintegrant that swells rapidly on contact with water, breaking the tablet apart to aid drug dissolution and absorption.
Question 6: First-pass metabolism predominantly occurs in which organ?
- Liver (Correct answer)
- Kidney
- Lung
- Stomach
Correct answer: Liver
After oral absorption, drugs enter the portal circulation and pass through the liver before reaching systemic circulation. Extensive hepatic metabolism reduces bioavailability — this is first-pass effect.
PSI Pharmaceutical Sciences 1
Which route of administration provides 100% bioavailability?