Pharmokinetics Flashcards
Which of the following is not a primary process in pharmacokinetics?
A) Absorption
B) Distribution
C) Receptor binding
D) Biotransformation
C
Which factor does not significantly affect drug absorption?
A) Drug solubility
B) Route of administration
C) Number of hydrogen bonds in the drug molecule
D) Surface area of the absorbing membrane
C
The first-pass metabolism occurs when drugs are taken:
A) Orally
B) Intravenously
C) Subcutaneously
D) Intramuscularly
A
The blood-brain barrier (BBB) primarily prevents the entry of:
A) Lipid-soluble molecules
B) Large, ionized molecules
C) Small, uncharged molecules
D) Psychoactive drugs
B
Which route of administration typically leads to the fastest drug effect?
A) Oral
B) Intramuscular
C) Intravenous
D) Rectal
C
Depot binding refers to:
A) The attachment of a drug to an active receptor
B) The binding of a drug to inactive sites such as fat or plasma proteins
C) The immediate metabolism of a drug by the liver
D) The rapid elimination of a drug through the kidneys
B
What is the primary organ responsible for drug metabolism?
A) Kidneys
B) Stomach
C) Liver
D) Lungs
C
The half-life of a drug refers to:
A) The time taken for the drug to reach peak concentration in plasma
B) The time taken for the drug concentration in plasma to decrease by half
C) The total duration of action of the drug
D) The time required for complete elimination of the drug
B
Ion trapping occurs when:
A) A drug changes form depending on pH, causing it to become trapped in a compartment
B) A drug binds to plasma proteins and is stored in the bloodstream
C) A drug crosses the blood-brain barrier and is stored in neurons
D) The kidneys actively reabsorb the drug instead of excreting it
A
Which of the following drugs would be absorbed best in the stomach (pH 2-3)?
A) A weak acid with a pKa of 3.5
B) A weak base with a pKa of 8.6
C) A weak base with a pKa of 9.0
D) A weak base with a pKa of 5.2
A
What is bioavailability, and how does it impact drug effectiveness?(2 marks )
Bioavailability refers to the percentage of an administered drug that reaches systemic circulation. It determines how much of a drug is available to exert its effect.
Why do drugs with high lipid solubility tend to reach the brain more quickly?(2 marks )
Lipid-soluble drugs can easily cross cell membranes and the blood-brain barrier (BBB), leading to faster penetration into the brain.
What is the difference between simple diffusion and facilitated diffusion in drug transport?(2 marks)
Simple diffusion occurs when drugs move across membranes without a transporter, driven by a concentration gradient.
Facilitated diffusion requires a carrier protein, but does not use energy.
Explain why intravenous (IV) administration bypasses first-pass metabolism.(2 marks)
IV drugs enter the bloodstream directly, avoiding the liver and gastrointestinal metabolism that occurs with oral drugs.
How does plasma protein binding affect drug distribution?(2 marks )
Drugs that bind to plasma proteins (e.g., albumin) are inactive while bound, reducing their immediate effect. Only free (unbound) drug is active.
Describe the four major processes of pharmacokinetics (absorption, distribution, metabolism, and excretion).( 6 marks)
Absorption: How a drug enters the bloodstream (affected by solubility, ionization, and route of administration).
Distribution: How the drug spreads in the body (depends on blood flow, binding to plasma proteins, and the blood-brain barrier).
Metabolism: Chemical modification of the drug (mainly in the liver) to make it easier to excrete.
Excretion: Elimination of the drug (mainly by the kidneys through urine, but also via bile, sweat, or breath).
Compare and contrast different routes of drug administration and their impact on drug onset, duration, and bioavailability.( 6 marks )
Intravenous (IV): Rapid onset, 100% bioavailability, short duration.
Oral: Slower onset, variable bioavailability due to first-pass metabolism, longer duration.
Inhalation: Very fast onset, high bioavailability, short duration.
Transdermal (patches): Slow onset, steady release, long duration.
Explain how pH and ionization influence drug absorption, using aspirin as an example.
Aspirin (pKa ~3.5) is a weak acid.
In the stomach (pH 2-3), aspirin remains non-ionized, making it lipid-soluble and easily absorbed.
In the small intestine (pH 5-6), aspirin becomes more ionized, reducing absorption.
Once aspirin enters the bloodstream (pH ~7.4), it gets trapped because it is ionized, preventing it from diffusing back into the stomach.
Describe the blood-brain barrier and its role in drug distribution. What types of drugs can cross it easily?( 6 marks)
The BBB is a selective barrier that protects the brain from toxins. It consists of tight junctions in capillary endothelial cells.
Lipid-soluble and small, uncharged drugs cross easily (e.g., heroin, nicotine).
Large or ionized molecules struggle to cross (e.g., many antibiotics).
Outline the key factors that contribute to individual differences in drug metabolism. ( 6 marks)
Genetics: Variations in liver enzymes (e.g., some East Asians lack efficient aldehyde dehydrogenase, leading to alcohol intolerance).
Age: Older people have slower liver metabolism, leading to longer drug half-life.
Sex Differences: Women generally have lower levels of gastric alcohol dehydrogenase, meaning more alcohol enters the bloodstream.
Chronic Drug Use: Long-term drug use can increase liver enzyme activity, leading to faster metabolism and tolerance.
