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PDA Test 3 > Absorption Lecture > Flashcards

Absorption Lecture Flashcards

1
Q

Define Absorption

A

Process by which unchanged drug proceeds from the site of administration to the site of measurement within the body

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2
Q

Define dose

A

How much drug is given

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3
Q

Define dosage form

A

How the drug is formulated (solid, solution, coated capsule, time-release)

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4
Q

Define Route of Administration

A

Oral, IV, nasal, etc

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5
Q

Define physicochemical properties of the drug

A

Size, lipid solubility, ionization, polarity, stability

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6
Q

Define anatomy and physiology at the site of absorption

A

Transit time, permeability, surface area, transporters, drug metabolism, and blood flow

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7
Q

What does absorption involve?

A

Passage across a biological membrane or tissue barrier

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8
Q

Define diffusion

A

Dependent upon a downward gradient of substance to be passed to the other side

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9
Q

Define facilitated diffusion

A

Made possible by a carrier molecule that the substance interacts with or a channel that in the “open” state allows with no affinity or interaction

  • Channels tend to have a much faster rate of passage vs transporters
  • Dependent on gradients
  • Can be inhibited if competing molecules crowd out the substance of interst
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10
Q

Define active transport

A

Carrier mediated
Energy dependent
Allows molecular movement of substance in opposition to its concentration gradient Shows saturation kinetics and can be inhibited

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11
Q

Define symporter

A

Co-transporter

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12
Q

Define antiportar

A

Anti-transporters

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13
Q

Define Fick’s Law of Diffusion

A

Quantifies the amount of a substance diffusing across a given surface area in a certain amount of time under a specified concenration gradient of the substance (“flux”)

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14
Q

Fick’s Law of Diffusion Equation

A 
J= D (Cout- Cin)/h
J= flux of substance
D= diffusion coefficient
h= thickness of the membrane of the barrier
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15
Q

What affects the passage of drugs across the GI cells into the body?

A
  • Variation in “transit time” and pH of the segments
  • Concentration variations
  • Presence of influx and efflux transport systems
  • Membrane potentials can promote or oppose movement of charged molecules
  • Osmotic effects of water movement
  • Enzymes can modify the drug
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16
Q

We are only ___ % human?

A

10!

The other 90% is bacteria cells

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17
Q

What affects drug absorption in the GI Tract?

A

Anatomy and pH changes

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18
Q

What is the paracellular pathway of absorption?

A

Between adjacent cells

  • Restricted to small, polar molecules
  • Must alter the tight junctions between cells
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19
Q

What is transcytosis/endocytosis of absorption?

A

Absorption into the lymphatic circulation via M cells of Peyer’s patches

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20
Q

What do M cells do?

A

Take up antigens and pathogens in the GI tract in order to potentially alert or cause a response in the immune system

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21
Q

Define surface area?

A

Important in drug uptake

- Orally: small intestine

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22
Q

What increases the surface area of the small intestine?

A

Folds, villi, microvilli

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23
Q

Define bioavailability

A

The fraction of administered drug that reaches the site of measurement in the body (usually done in the peripheral venous blood)

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24
Q

Hepatic first- pass metabolism?

A

Reduce oral drug bioavailability

25
Q

Tablets or capsules administration requires?

A

Involves both disintegration of the solid form and dissolution into gastric fluid

26
Q

What is the driving force in solutions?

A

Is the free drug concentration in solution

27
Q

What properties is drug permeability strongly influenced by?

A

Lipophilicity
Charge
Size
Presence of Facilitated or Active Transport

28
Q

What is lipid solubility related to?

A

Drug passive permeability across cell membranes

29
Q

Why is lipid solubility important?

A

Drugs must dissolve in and diffuse across cell membranes composed mostly of a phospholipid bilayer
- Key factor for rate of penetration across a barrier

30
Q

How does ionization play into drugs?

A

Unionized species of a weak acid or base readily crosses membranes

  • Most organic acids are unionized at a pH < pK
  • Most organic bases are unionized at a pH > pK
31
Q

How does pH play into drugs?

A

pH differs in different compartments of the body and can alter drug action

32
Q

How does drug size play into absorption?

A

Larger molecules have less of an ability to cross membranes or tissue barriers
- But they can cross through pores or channels between cells or by receptor-mediated transport systems

33
Q

How does blood flow affect absorption?

A

This is what carries the drug away once the drug has crossed its limiting barrier membrane
- Blood flow influences Cin

34
Q

Blood flow in the small intestine? stomach? lungs?

A

1 L/min
0.15 L/min
5-7 L/min

35
Q

What if there is a sufficiently high permeability?

A

Blood flow is rate limiting

  • Increasing blood flow increases absorption
  • This are called high-extraction ratio drugs
36
Q

What about low-extraction ratio drugs?

A

Low permeability

Mostly affected by enzyme induction or inhibition or extent of protein binding

37
Q

What is Oral Enteral Routes of Administration?

A

Convenient and economical but require cooperation

  • Not prime for drugs that are poorly soluble, unstable, slowly absorbed or metabolized by the liver or gut enzymes
  • Efflux transporters may exclude them even if they make it to the GI cells
38
Q

What is Sublingual Enteral Routes of Administration?

A

Rapid for lipid soluble drugs

Avoids GI tract and first pass metabolism

39
Q

What is Rectal Enteral Routes of Administration?

A

Used where patient is unconscious or vomiting

  • Somewhat unpredictable and irregular
  • First pass metabolism hits 50%
40
Q

What is IV or infusion Parenteral Routes of Administration?

A

Direct into the blood
Very rapid delivery
No barriers to absorption
Invasive and carries increased chance of adverse reactions

41
Q

What is IM Parenteral Routes of Administration?

A

Rapid absorption into circulation from aqueous solution, slow from non-aqueous

  • Delivery of large, polar or unstable compounds that are poorly absorbed from external sites but can cross leaky muscle capillaries
  • Can be painful, inflammatory or toxic via this route but is easier than IV
42
Q

What is SubQ Parenteral Routes of Administration?

A

Overcomes permeability limitations to absorption of classic enteral routes

43
Q

What is Intraspinal or intrathecalParenteral Routes of Administration?

A

“into the subarachnoid space in spinal cord or brain”

  • Deliver drug to the CNS overcoming the BBB
  • Often painful, risky, and poor distribution
44
Q

What is Intra-arterial Parenteral Routes of Administration?

A

“into the arterial blood circulation”

Used for delivery of some imaging agents or for local delivery to a tissue (cancer chemotherapy)

45
Q

What is transdermal administration?

A

Good for patches and long-term delivery

- Avoid first-pass metabolism

46
Q

What is intraocular administration?

A

For local delivery to eye

47
Q

What is inhalational or pulmonary administration?

A

Absorption of gaseous or volatile drugs
Local lung delivery
- Avoids first-pass in liver

48
Q

What is intranasal delivery?

A

Delivery to nasal mucous membranes and sinuses

49
Q

Transporter activities include?

A

Control influx of essential nutrients and the efflux of cellular waste and environmental toxins

  • Can be drug specific and are used to transport drugs or chemicals through a membrane
  • Can be facilitated or active
50
Q

ATP Binding Casette Type Subfamily

A

Primary active transporters

  • Relay on ATP
  • Example: P-glycoprotein “efflux” system
51
Q

Solute Carrier Type Subfamily

A

Facilitated and ion-coupled secondary trasnporters

  • Drug targets or alter ADME/PK
  • Examples: SERT and DAT
52
Q

What is the P-glycoprotein system?

A

Efflux system

Protects the BBB by ejecting anything that enter and shouldn’t be in the brain back into the blood

53
Q

What are transporters affect drug pharmacokinetics?

A

Found in GI tract, renal, and hepatic epithelia

  • Selectively absorb and help eliminate endogenous substances and xenobiotics such as drugs; work in concert with drug-metabolizing enzymes
  • Play roles in tissue-specific distribution and may facilitate or impair “drug targeting” efforts in therapy
54
Q

Drug level can lead to what?

A 
Absorption into the intestine 
Therapeutic effects
Adverse drug effects
Metabolism and excretion via the liver
Excretion via the kidneys
55
Q

What can transporters at the intestinal mucosa do?

A

Facilitate or impede drug movement into the circulation

- Intestinal enzymes can also break drugs down before they pass into the circulation

56
Q

How does the liver effect elimination?

A
  • Metabolism to some type of primary metabolite back into the blood if the kidney can handle it
    OR
  • Metabolize it in the liver and then put it in the bile so it can be removed via feces
57
Q

What are clearance organs?

A

Modified the effect of the transporter (decrease uptake or excretion)
Raise the concentration in the plasma and the target organ
Increasing toxicity

58
Q

What are toxicological target organs?

A

Increases uptake or decrease efflux than you increase exposure/concentration

59
Q

What is Multidrug Resistance Protein-4

A

Associated with resistance to antiviral nucleoside analogs that are designed to be utilized as a chain terminator of viral DNA synthesis in diseases such as AIDS and hepatitis

PDA Test 3 (7 decks)

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