Sstock - Drug Absorption

Front 1

Name the different types of Passive Transfer mechanisms for drug absorption.

Back 1

Aqueous Diffusion; Lipid Diffusion; Carrier Facilitated Diffusion

Front 2

Characteristics of Aqueous Diffusion

Back 2

Involves pores through which H2O, ions, small molecules can pass; decreases when MW exceeds 100 > 200 & with bulky molecules

Front 3

Transfer of lipid soluble substances is proportional to:

Back 3

concentration gradient of nonionized form across the membrane & the lipid/water partition coefficient of nonionized form of the drug

Front 4

With regards to acids and bases, most drugs are:

Back 4

weak acids or weak bases; exist as both ionized and nonionized forms

Front 5

ratio of ionized fraction of a drug is dependant upon:

Back 5

the ionization constant (pKa) of the drug; pH of the body fluid in which the drug is present

Front 6

at a pH below a drug's pKa, that drug is:

Back 6

acids are largely in nonionic form; bases are largely in ionic form

Front 7

at a pH above a drug's pKa, that drug is:

Back 7

acids are largely in IONIC form; bases are largely in NONIONIC form

Front 8

How does being in ionized or nonionized form affect lipid solubility?

Back 8

Ionized form leads to poor lipid solubility, while nonionized form leads to high lipid solubility.

Front 9

Ultimate factor influencing absorption?

Back 9

lipid solubility of nonionized form of the drug.

Front 10

What is ion trapping?

Back 10

If a pH difference exists across a membrane, fraction ionized may be significantly larger on one side than on the other. At equilibrium, concentration of nonionized form will be equal on both sides but there will be more TOTAL drug on side where degree of ionization is greater.

Front 11

Describe Carrier-Facilitated Diffusion:

Back 11

substance forms complex with moleucle within membrane; carrier molecule has degree of specificity; complex travels from one side to another then substance released;

Front 12

Carrier-facilitated diffusion limited by what?

Back 12

# of binding sites on carrier molecule; concentration gradient (will only go downhill, i.e. NOT against gradient

Front 13

Describe Active transport:

Back 13

similar to carrier-facilitated diffusion, but will go AGAINST a concentration gradient; requires net expendature of energy

Front 14

Active transport ca be reduced by:

Back 14

non-competitive inhibition (interference with cellular energy production); competitive inhibition (when similar molecules compete for limited sites on carrier molecule).

Front 15

Define bioavailability:

Back 15

rate(speed) and extent(amount) of absorption of unchanged drug from its dosage form into the blood

Front 16

Compare "chemical equivalence", "pharmaceutical equivalence", "biological equivalence", and "therapeutic equivalence".

Back 16

Chemcial equivlance refers to the same amount of active ingredient; pharma equivalence refers to same amount of both active and inactive ing; bio equivlance > same bioavailability; therapeutic equivalence > same effectiveness

Front 17

A generic drug being chemically equivalent doesnt guarantee what?

Back 17

that it is equally bioavailable; generics that arent equally bioavailable likely wont provide same therapeutic effect.

Front 18

What is the first pass effect?

Back 18

the initial biotransformation: upper GI > hepatic portal. oral more extensive than rectal.

Front 19

Degree of hepatic clearance depends on what?

Back 19

Comparison of the blood level of drug entering liver with blood level after exiting. Also: degree of binding to plasma proteins; rate of biliary excretion; rate of hepatic biotransformation; rate of transport into liver cells

Front 20

Major reasons for oral administration of a drug include:

Back 20

convenient, safe, economical, strerility a non-issue

Front 21

Why would a patient take a drug under the tongue?

Back 21

rapid absorption, get higher concentration into blood b/c it doesnt go through liver, get destroyed by GI secretions, complex with food/metals

Front 22

Describe drug absorption in the gastric mucosa:

Back 22

pH of 1-3.5. Organic acids well absorbed b/c they are almost completely non-ionized at gastric pH. ethyl alcohol well absorbed.

Front 23

How do bases accumulate in the stomach?

Back 23

IV administered bases can be non-ionized at blood pH, then pass into gastric area (lower pH), become ionized, cant return to blood. ION TRAPPING!

Front 24

What type of drug is most likely to be absorbed in the intestine?

Back 24

weak bases; intestine has pH of ~5.3.

Front 25

Name 3 factors that influence stomach and intestine absorption:

Back 25

1. Pharma Formulation (enteric coating, sustained-release formulations) 2. GI motility 3. Presence of food

Front 26

When should drugs not be given orally?

Back 26

drugs cause N &V, unable unwilling to swallow, destruction by GI secretions, not absorbed by GI mucosa

Front 27

What is the rectal pH? Drugs administered rectally should be?

Back 27

7-8; isotonic with plasma

Front 28

Intra-arterial injections are primarily used for what?

Back 28

local perfusion of an organ, e.g. cancer chemo; diagnostics, e.g. carotid injection for vascular visualiztion

Front 29

Characteristics of Intramuscular injections:

Back 29

made deep into muscle; quick absorption; small molecules > capilaries, large molecules > lymphatics

Front 30

What is a depot form?

Back 30

promote gradual absorption over long period of time; poorly soluble at tissue pH, suspended in relatively insoluble vehicle

Front 31

Advantages to Parenteral drug administration?

Back 31

immediate to rapid response, predictable response, always available, avoids GI secretions, psych benefit

Front 32

DISadvantages of parenteral drug admin?

Back 32

self-admin impractical, sterility required, discomfort, hazardous (irritation, allergy, overdose more difficult to control)

Front 33

Why do general anesthetics equilibrate almost instantly with the blood?

Back 33

relatively high L/W partition coefficients, very small molecular radii, readily permeable alveolar membranes

Front 34

Impaction of aerosole particles increased by?

Back 34

patient holding breath after inhalation, adding hygroscopic substance

Front 35

Drugs commonly aerosolized include:

Back 35

epinephrine or isoproterenol (asthma), antiobiotics (lungs), mucolytic enzymes

Front 36

What is the difference between drugs applied to the skin vs. drugs applied via transdermal patch?

Back 36

skin > intended for local effects

transdermal patch > systemic effects, penetration dependant on pore size in patch

Front 37

Drugs applied to skin for treatment of local problems penetrate at rates determined by ?

Back 37

their L/W partition coefficient

Front 38

Percutaneous absorption can be increased by what?

Back 38

incorporation into a fatty vehicle; inunction; prior application of a keratolytic (e.g. salicylic acid)

Front 39

What does dimethyl sulfoxide do?

Back 39

promotes absorption of many chemicals through the skin; treatment option for interstitial cystitis