Podcast
Questions and Answers
Which of the following is NOT a factor related to the patient that affects drug absorption?
Which of the following is NOT a factor related to the patient that affects drug absorption?
Which of the following is a factor related to the drug that affects its absorption?
Which of the following is a factor related to the drug that affects its absorption?
What is the process by which a drug is distributed between blood and tissues after absorption?
What is the process by which a drug is distributed between blood and tissues after absorption?
Which of the following areas is likely to have slower distribution of a drug?
Which of the following areas is likely to have slower distribution of a drug?
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What happens when a drug is bound to plasma proteins?
What happens when a drug is bound to plasma proteins?
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If a patient on warfarin (highly protein bound) also takes aspirin, what is likely to happen?
If a patient on warfarin (highly protein bound) also takes aspirin, what is likely to happen?
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Which statement about drug absorption is correct?
Which statement about drug absorption is correct?
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What is the primary factor affecting the absorption of an acidic drug?
What is the primary factor affecting the absorption of an acidic drug?
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Which of the following statements about drug distribution is true?
Which of the following statements about drug distribution is true?
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What is the primary factor determining a drug's ability to cross the blood-brain barrier?
What is the primary factor determining a drug's ability to cross the blood-brain barrier?
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Which statement about plasma protein binding is correct?
Which statement about plasma protein binding is correct?
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Which factor is least likely to affect drug absorption?
Which factor is least likely to affect drug absorption?
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What is the primary function of the blood-brain barrier?
What is the primary function of the blood-brain barrier?
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Which route of drug administration can bypass the first-pass effect?
Which route of drug administration can bypass the first-pass effect?
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What is the primary mechanism by which drugs are eliminated from the body?
What is the primary mechanism by which drugs are eliminated from the body?
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Which factor can increase the free concentration of a highly protein-bound drug like warfarin?
Which factor can increase the free concentration of a highly protein-bound drug like warfarin?
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What is bioavailability?
What is bioavailability?
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Which factor can affect the bioavailability of a drug?
Which factor can affect the bioavailability of a drug?
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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)
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Description
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.
