Absorption

Question 1

What factors determine given drug’s ability to cross biological membrane

Answer 1

size, degree of ionization, concentration gradient, lipid solubility,

Question 2

Mechanisms drugs cross biological membranes

Answer 2

Passive diffusion (aqueous via aquaporins and lipid soluble drugs directly diffusing), Active transport, Endocytosis, Facilitated diffusion

Question 3

Most important mechanism for drugs to cross biological membranes

Answer 3

lipid soluble drugs diffusing across membrane

Question 4

Enteral Routes

Answer 4

Oral and rectal

Question 5

Parenteral Routes

Answer 5

IV, Inhalational, subcutaneous, imtramuscular, transdermal, sublingual, buccal, etc

Question 6

Oral Route (adv/dis)

Answer 6

systemic effects, variable bioavailability, encounters enterohepatic circulation, man manipulate rate of absorption, food delays absorption

Question 7

Rectal

Answer 7

Systemic effects, can use for those who are vomitting, unconscious, post GI surgery, uncooperative, low pts acceptance, variable bioavailability, less efficient metabolism than oral

Question 8

IV route

Answer 8

100% bioavailable, most rapid/direct route, high potential for toxicity, can introduce infectious agents, difficult reversal of effect

Question 9

IM

Answer 9

approach bioavailability of IV, Can use depot forms or oil suspensions for slower/sustained absorption, pain/necrosis if high pH, microbial contamination

Question 10

Inhalational (systemic)

Answer 10

volatile gases; high bioavailability but can be addicting

Question 11

subcutaneous

Answer 11

systemic, generally approaches 100% bioavailability, slower, constant absorption rate, limited dose volume, only for non-irritating drugs

Question 12

Sublingual

Answer 12

systemic, high bioavailability, rapid onset, avoids first pass metabolism, good for lipid soluble/potent drugs

Question 13

transdermal

Answer 13

systemic, avoids first pass metabolism, avoid ADR related to hepatic actions, potential for unexpected accumulation/toxicity, need nonsensitizing/nonirritating yet potent d rug

Question 14

Local routes

Answer 14

Aural, nasal, throat, vaginal, ocular/conjunctival, inhalational

Question 15

Inhalational (local)

Answer 15

(particles) increase local topical effects in lung/lower systemic effect, effects depend on particle size

Question 16

Bioavailability

Answer 16

extent of unchanged drug reaching systemic circulaiton; determined by [AUC (from route)/AUC (
IV)]

Question 17

What form of the weak acid/base drug crosses membranes?

Answer 17

unionized form (AH, B)

Question 18

Ion trapping

Answer 18

Have two compartments with different pHs separated by membrane –> ionized form of the drug gets trapped on one side of membrane. Total drug concentration greater on side where ionization is greater

Question 19

What kind of solution will trap a weakly acidic drug?

Answer 19

weak base

Question 20

Barriers in body with tight junctions

Answer 20

GI, Blood brain barrier, placenta, renal tubules

Question 21

Characteristics of drug that can easily cross membranes

Answer 21

small, uncharged, high lipid solubility, has large concentration gradient

Question 22

What does plasma protein binding do to a drug

Answer 22

Creates protein-drug complex that cannot diffuse/cross membrane; increases half-life, decrease Vd, decrease ability to enter blood brain barrier or distribute to tissue (affects distribution/metabolism/excretion)

Question 23

Protein-binding displacement

Answer 23

Give second drug that will bind to plasma protein and cause displacement of first drug

Question 24

When you should be concerned about protein-binding displacement interactions

Answer 24

Narrow therapeutic index of displaced drug, displacing drug started in high doses, Vd of displaced drug small, response to drug occurs more rapidly than redistribution

Question 25

Vd

Answer 25

volume of distribution–extend to which drug is distrubuted

Question 26

relationship between Cp and Vd

Answer 26

inverse; more in plasma means less distributed to tissues

Question 27

Volumes of water compartments in body

Answer 27

Plasma/blood - 3-5 L
Extracellular water = 12-15L
Total body water= 42 L
Other compartments (sequestering) = >50 L

Question 28

High Vd

Answer 28

less drug in plasma, more in tissue

Question 29

Low Vd

Answer 29

more drug in plasma

Question 30

Variation in Vd due to…

Answer 30

body size, fat vs lean composition, changes in protein binding

Question 31

relationship between loading dose and Vd

Answer 31

LD = CpxVd

Question 32

How to determine effect of dose on Cp

Answer 32

Cp = Dose/ Vd

Question 33

Where is drug if Vd= 13

Answer 33

drug mostly in extracellular space