Drug Movement

Question 1

Aqueous diffusion

Answer 1

Passive diffusion through aqueous channels in the paracellular junctions, driven by concentration gradient

Question 2

Lipid diffusion

Answer 2

Important pathway for most drugs, most important limiting factor (lipid barriers separate aqueous compartments), determined by a drug’s lipid:aqueous partition coefficient, pH, pKa

Question 3

Special carriers

Answer 3

Selective, saturable, inhibitable, active transport or facilitated transport, only those with appropriate characteristics can utilize this mechanism

Question 4

Endocytosis/exocytosis

Answer 4

Process of binding to cell surface receptor, engulfment by cell membrane, carrying into the cell in vesicles, requires specific receptors

Question 5

Pharmacokinetics ADME

Answer 5

Absorption, distribution, metabolism, excretion

Question 6

Fick’s law of diffusion

Answer 6

Rate of diffusion is equal to (available surface area x concentration gradient) / (resistance of membrane x thickness of membrane)

Question 7

Partition coefficient

Answer 7

Lipid solubility of a drug in its non-ionized form

Question 8

Dissociation constant

Answer 8

pKa, pH value at which the substance exists in equal concentrations of ionized and non-ionized forms

Question 9

Henderson-Hasselbach equation

Answer 9

pH = pKa + log [nonprotonated species] / [protonated species]

Question 10

Acid pH < pKa

Answer 10

[A-] < [HA]

Question 11

Acid pH > pKa

Answer 11

[A-] > [HA]

Question 12

Base pH < pKa

Answer 12

[B] < [BH+]

Question 13

Base pH > pKa

Answer 13

[B] > [BH+]

Question 14

pH of the blood

Answer 14

7.4

Question 15

Partition coefficient

Answer 15

Ratio of the drug concentrations in two different solutions, [Drug in organic solvent] / [Drug in water]