Pharmacokinetics MCQ

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Questions and Answers

Which mechanism of drug absorption involves the drug binding to a cell membrane and being engulfed?

  • Facilitated diffusion
  • Active transport
  • Passive diffusion
  • Endocytosis (correct)

Which factor negatively affects the absorption of local anesthetics when co-administered?

  • Coadministration of vitamin B12
  • Coadministration of adrenaline (correct)
  • Coadministration of ferrous iron
  • Coadministration of calcium

What happens to weak acids when placed in an alkaline solution?

  • They become unchanged
  • They become more lipid-soluble
  • They become more water-soluble
  • They become more ionized (correct)

What can be inferred about a drug with high lipid solubility in terms of absorption?

<p>Increased absorption (D)</p> Signup and view all the answers

What does the term bioavailability refer to?

<p>Percentage of drug reaching systemic circulation (D)</p> Signup and view all the answers

Which route of drug administration guarantees 100% bioavailability?

<p>Intravenous (A)</p> Signup and view all the answers

What is the 'first pass effect' in pharmacology?

<p>Metabolism of the drug before it reaches systemic circulation (A)</p> Signup and view all the answers

Which drug is significantly affected by the hepatic first pass effect?

<p>Propranolol (D)</p> Signup and view all the answers

What is the primary focus of pharmacokinetics?

<p>Drug absorption, distribution, metabolism, and excretion (A)</p> Signup and view all the answers

Which route of drug administration has the fastest absorption rate?

<p>Intravenous (A)</p> Signup and view all the answers

Which factor increases drug absorption?

<p>High lipid solubility (A)</p> Signup and view all the answers

What role does metabolism play in pharmacokinetics?

<p>Breaks down drugs into metabolites (C)</p> Signup and view all the answers

What is the effect of calcium on the absorption of tetracyclines?

<p>Decreases absorption (B)</p> Signup and view all the answers

What is the term for the pH at which drug ionization is equal to its unionized form?

<p>Dissociation constant (pKa) (D)</p> Signup and view all the answers

Which type of transport involves the movement of substances from high to low concentration without energy?

<p>Passive diffusion (D)</p> Signup and view all the answers

Which factor related to patients affects drug absorption?

<p>Route of administration (B)</p> Signup and view all the answers

What is the primary function of biotransformation in pharmacology?

<p>To convert lipid-soluble drugs into water-soluble metabolites (A)</p> Signup and view all the answers

Which process can shorten the effective duration of a drug in the body?

<p>Enzyme induction (C)</p> Signup and view all the answers

Which factor primarily influences the extent of drug distribution in the body?

<p>Plasma protein binding (B)</p> Signup and view all the answers

What is a significant consequence of a drug having a long elimination half-life?

<p>Prolonged drug action in the body (C)</p> Signup and view all the answers

What occurs to a prodrug in the body during metabolism?

<p>It is transformed into an active form (A)</p> Signup and view all the answers

How does inflammation affect the permeability of the blood-brain barrier?

<p>It can enhance permeability (C)</p> Signup and view all the answers

Which drug is associated with significant teratogenic effects when it crosses the placental barrier?

<p>Alcohol (C)</p> Signup and view all the answers

What is the result of enzyme inhibition on a drug's pharmacological actions?

<p>Enhanced toxicity (A)</p> Signup and view all the answers

Flashcards

Pharmacokinetics

The study of how drugs are absorbed, distributed, metabolized, and excreted in the body.

Drug Absorption

The process by which a drug moves from the site of administration into the bloodstream.

Passive Diffusion

Drug movement across membranes from a higher concentration to a lower concentration, without energy.

Active Transport

Drug movement across membranes against a concentration gradient, requiring energy.

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Intravenous Administration

Drug administration directly into the bloodstream, resulting in the fastest absorption.

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Drug Metabolism

The process of converting a drug into a less active form or a metabolite for elimination.

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Drug Excretion

The process of eliminating drugs, and/or their metabolites from the body.

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Lipid Solubility

The ability of a drug to dissolve in fats; influences absorption.

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Ionization

The process by which a molecule gains or loses a charge

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pKa

The pH at which a drug is half ionized and half unionized

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Route of administration

The path by which a drug is introduced into the body.

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Active Transport

Movement of molecules against their concentration gradient, requiring energy.

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Facilitated Diffusion

Movement of molecules across a membrane with the help of a carrier protein, down their concentration gradient.

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Passive Diffusion

Movement of molecules from high to low concentration across a membrane, no energy required.

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Endocytosis

The process where a cell engulfs material from outside the cell by forming a vesicle.

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Oral Drug Administration (in shock)

Least suitable route during shock due to slow absorption and potential delays in effect.

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Weak Acids in Alkaline Solution

Become more ionized in alkaline solutions.

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Drug Absorption Mechanism: Endocytosis

Drug absorption mechanism where a cell surrounds and internalizes a drug.

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Co-administration of Adrenaline (and local anesthetics)

Decreases absorption of local anesthetics due to vasoconstriction effects.

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Most Efficient Drug Form

Solution, more efficient than suspensions, tablets, and capsules.

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High Lipid Solubility

Results in increased drug absorption.

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Higher pKa Value (Weak Acid)

Indicates a weaker acid.

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Lipid Soluble Drug Absorption

Drug absorption primarily through passive diffusion in a lipid-soluble state.

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Bioavailability

Percentage of drug reaching systemic circulation after administration

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100% Bioavailability Route

Intravenous administration.

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Hepatic First-Pass Effect

Drug metabolism by the liver before reaching systemic circulation

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Inactive drug form

Drug form not able to be metabolized or excreted

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Toxic metabolite

Harmful substance formed from drug transformation.

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Plasma protein binding

Drugs attaching to proteins in blood.

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Drug distribution

How drugs move through the body.

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Liver drug metabolism

Primary organ where drugs are changed.

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Enzyme induction

Increase in enzymes that break down drugs.

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Drug excretion (primary site)

Kidneys are the main organs for drug removal from the body.

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Elimination half-life (t1/2)

Time for drug concentration to drop by half.

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Free drug

Active and unbound drug in the bloodstream.

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Biotransformation

Changing a drug into water-soluble forms for excretion.

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Blood-brain barrier

Protective barrier between blood & brain tissue to stop unwanted components.

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Teratogenicity

Harmful effect of a drug or exposure on a fetus.

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Enzyme inhibition

Decreased enzyme activity to slow down drug breakdown.

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Drug absorption (primary site)

Small intestine is the primary site for drug absorption.

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First-pass metabolism

Drug metabolism in the liver when absorbed from the gut.

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Prodrug

Inactive drug that is changed into an active form by the body.

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Inflammation effect on BBB

Inflammation increases permeability of the blood-brain barrier.

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Study Notes

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 (t1/2): 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.

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