18 Questions
Which of the following is NOT a factor related to the patient that affects drug absorption?
Chemical structure of the drug
Which of the following is a factor related to the drug that affects its absorption?
Molecular size
What is the process by which a drug is distributed between blood and tissues after absorption?
Distribution
Which of the following areas is likely to have slower distribution of a drug?
Muscle
What happens when a drug is bound to plasma proteins?
The drug is inactive
If a patient on warfarin (highly protein bound) also takes aspirin, what is likely to happen?
Both drugs will compete for protein binding
Which statement about drug absorption is correct?
Lipid-soluble drugs are readily absorbed through cell membranes
What is the primary factor affecting the absorption of an acidic drug?
Degree of ionization
Which of the following statements about drug distribution is true?
Lipid-soluble drugs can readily cross the blood-brain barrier
What is the primary factor determining a drug's ability to cross the blood-brain barrier?
Lipid solubility
Which statement about plasma protein binding is correct?
Highly protein-bound drugs have a smaller volume of distribution
Which factor is least likely to affect drug absorption?
Route of administration
What is the primary function of the blood-brain barrier?
To facilitate the passage of highly lipophilic drugs into the brain
Which route of drug administration can bypass the first-pass effect?
Both b and c
What is the primary mechanism by which drugs are eliminated from the body?
Metabolism (biotransformation)
Which factor can increase the free concentration of a highly protein-bound drug like warfarin?
Concomitant administration of a drug that competes for the same binding site on plasma proteins
What is bioavailability?
The fraction of a drug that reaches the systemic circulation unchanged after administration
Which factor can affect the bioavailability of a drug?
Both a and b
Study Notes
Pharmacokinetics
- Deals with the study of what the body does to the drug
- A.D.M.E. stands for Absorption, Distribution, Metabolism, and Excretion
Absorption
- Definition: Movement of the drug from its site of administration to the bloodstream
- Physiological factors affecting absorption:
- Factors related to the patient: route of administration, absorbing surface, systemic circulation, and drug stability in gut contents
- Factors related to the drug: water and lipid solubility, ionization, molecular size, and dosage form
- Weak acids or weak bases are more readily absorbed in the small intestine than strong acids and bases
- Stronger acids can be absorbed in the stomach
Ionization
- Ionized drugs are water soluble and have poor absorption through the stomach, blood-brain barrier (BBB), and placenta
- Non-ionized drugs are lipid soluble and have better absorption
- Absorption of acidic drugs is better in acidic medium, and basic ones are better in basic medium
Distribution
- Process by which a drug is distributed between blood and tissues after absorption
- Body compartments: plasma, interstitial, intracellular, separated by capillary walls and cell membranes
- Factors affecting distribution:
- Protein-binding
- Water soluble vs. fat soluble
- Blood-brain barrier
- Areas of rapid distribution: heart, liver, kidneys, brain
- Areas of slow distribution: muscle, skin, fat
Plasma Protein Binding
- Some drugs bind to plasma proteins
- Drug bound to plasma proteins is inactive
- Example: Warfarin is highly protein bound (99%)
- Aspirin binds to the same site on serum proteins as does warfarin, causing displacement of warfarin and increased free level
Bioavailability
- Fraction of unchanged drug reaching the systemic circulation following administration by any route
- Factors affecting bioavailability:
- Absorption
- First pass effect (pre-systemic elimination)
Metabolism (Biotransformation)
- Process by which lipid soluble drugs are converted to water soluble drugs for excretion
- Most drug biotransformation occurs in the liver, but drug-metabolizing enzymes are in many other tissues (gut, kidneys, brain, lungs, and skin)
Test your knowledge on which characteristics a drug must possess to easily cross the blood-brain barrier. Learn about the importance of drug lipophilicity in crossing this barrier and its implications. Challenge yourself with questions on drug displacement and its effects on free drug levels in the body.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
