Pharmacokinetics MCQ

Pharmacokinetics MCQ

• Pharmacokinetics: Focuses on drug absorption, distribution, metabolism, and excretion.
• Drug absorption: Passage of a drug from the site of administration to systemic circulation.
• Primary mechanism: Passive diffusion; active transport also exists.
• Factors affecting Absorption:
  • Lipid solubility: High is better
  • Ionization: Low pH for weak acids, high pH for weak bases improves absorption
  • Drug solubility
  • Route of administration (Oral, IV, etc).
• Factors influencing drug metabolism:
  • Enzyme induction/inhibition
  • Co-administration of other drugs
• Factors related to patients:
  • Ionization
  • Route of administration
• Hepatic first-pass effect: Metabolism of a drug by the liver before reaching systemic circulation. Propranolol is affected by the hepatic first-pass effect.
• Bioavailability: Percentage of a drug reaching systemic circulation unchanged. IV has 100%. Oral is affected by first pass.
• Biotransformation: (Metabolism): Converting drugs into water-soluble metabolites
  • Importance: Increased drug excretion, reduced toxicity, alteration of pharmacological effects
• Drug binding to plasma proteins: In inactive form, affects distribution.
• Blood-brain barrier: Prevents certain drugs from entering the brain.
• Placental barrier: Certain drugs can cross and cause teratogenicity (birth defects).
• Enzyme induction: Increased metabolism of drugs, and reduced drug efficacy/half-life. Increased absorption rate.
• Enzyme inhibition: Decreased metabolism of drugs and increased drug toxicity
• Major sites for drug metabolism: Liver.
• Primary sites for drug excretion: Kidneys
• Elimination half-life (t_1/2): Time for half the drug to be eliminated.
• First-pass effect: Reduction in drug bioavailability due to initial metabolism in the liver.

General Pharmacology MCQ (Specific Questions)

• Primary focus of pharmacokinetics: Drug absorption, distribution, metabolism, and excretion.
• Drug absorption: Absorption across biological membranes is primarily via passive diffusion.
• Absorption process: Drug movement across membrane from site of administration to systemic circulation.
• Main drug absorption mechanism (biological membranes): Passive diffusion
• Energy requirement for drug movement: Active transport requires energy (e.g. endocytosis).
• Fastest absorption route: Intravenous.
• Factors that increase drug absorption: High lipid solubility, low pH for weak acids, and high for weak bases.
• Role of metabolism: Breakdown drugs into metabolites.
• Effect of calcium on tetracycline absorption: Decreases absorption.
• pKa: pH at which ionization of a drug is equal to its unionized form.
• Factors affecting drug absorption: Systemic circulation, vascularity, and nature of the compound.
• Transport types:
  • Passive diffusion (no energy)
  • Active transport (energy required for movement)
  • Facilitated diffusion (no energy, facilitated by a carrier).
• Least suitable route during shock: Oral.
• Weak acids in alkaline solutions: Become more ionized.
• Drug absorption mechanism (envelopment): Endocytosis
• Local anesthetic absorption decrease: Co-administration.
• Efficient drug form (absorption): Solution.
• High lipid solubility effect: Increased absorption.
• Effect of higher pKa on weak acid: Weaker acid.