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Internal Medicine > Pharmacokinetics 1 drug administration, absorption, and distribution > Flashcards

Pharmacokinetics 1 drug administration, absorption, and distribution Flashcards

1
Q

What are the two routes of administration?

A
  1. alimentary canal –> enteral administration
  2. non-alimentary routes –> parenteral administration
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2
Q

**

What are considered enteral routes?

A
  • oral
  • sublingual and buccal
  • rectal
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3
Q

Advantages and disadvantages of oral administration?

A

A: easy, safe, convienent
D: limited, erratic absorption of some drugs; chance of first pass inactivation in liver

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4
Q

Advantages and disadvantages of rectal administration

A

A: alternative to oral route
local effect on rectal tissue
D: poor or incomplete absorption; chance of rectal irritation

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5
Q

Advantages and disadvantages of sublingual administration

A

A: rapid onset, not subject to first pass inactivation
D: drug must be easily absorbed from oral mucosa

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6
Q

What are examples of parenteral administration?

A
  • inhalation
  • injection
  • topical transdermal
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7
Q

Advantages and disadvantages of inhalation administration

A

A: rapid onset; direct application for respiratory disorders; large SA for systemic absorption
D: chanCe of tissue irritation
patient compliance sometimes problem

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8
Q

Advantages and disadvantages of injection administration

A

A: provides more direct administration to target tissue; rapid onset
D: chance of infection if sterility is not maintained

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9
Q

Advantages and disadvantages of topical administration

A

A: local effects on surface of skin
D: only effective in treating outer layers of skin

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10
Q

Advantages and disadvantages of transdermal administation?

A

A: introduces drug into body w/o breaking skin;can provide steady prolonged delivery via medicated patch
D: drug must be able to pass through dermal layers intact

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11
Q

Oral

A
  • high degree of lipid solubility to pass through GI mucosa
  • large SA of intestinal microvilli on small intestine to enhance entry into body
  • first pass (inactivation) in liver metabolized and destroyed (Drug transported directly to portal vein)
  • drug enters in fairly controlled manner, final amt and rate less predictable
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12
Q

Sublingual and Buccal

A
  • drugs can reach systemic circulation without being subjected to first pass inactivation in liver
  • faster effect than swallowing drug (acute angina)
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13
Q

Rectal

A
  • good for unconscious or vomiting
  • absorbed poor, irrtation of rectal muscosa
  • to treat local conditions (hemorrhoids)
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14
Q

parental

A
  • more directly to target site
  • more predictable quanity of drug
  • usually not subject to first pass inactivation in liver
  • inhalation, injection, topical, transdermal
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15
Q

inhalation

A
  • rapid entry into bloodstream through diffusion into pulmonary circulation
  • limited ability to predict exactly how much drug reaches lungs due to patients compliance and drug particles may be trapped by cilia and mucus
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16
Q

Injection

A
  • systemically or locally
  • IV
  • intraarterial
  • subcutaneous
  • intramuscular
  • intrathecal
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17
Q

IV injection

A
  • frequently resulting in peak levels almost instantaneously and reach target site rapidly
  • IV cannula (line) allow prolonged and steady infusion
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18
Q

intra-arterial injection

A
  • relative difficult and dangerous procedure
  • occasionally used in chemotherapy to minimize exposure of drug to healthy tissue
  • radiopaque dyes for various diagnostic procedure
19
Q

subcutaneous (SC) injection

A
  • relatively slower, more prolonged release into the systemic circulation (eg local anesthesia, insulin, and hormonal contraceptive products)
20
Q

intramuscular (IM) injection

A
  • easily accessible (eg botulism toxin for hyperexcitable muscles)
  • relatively steady, prolonged release
  • relatively rapid effect (within a few minutes) while avoiding the sudden, large increase in plasma levels seen with IV injection
21
Q

intrathecal injection

A
  • deliver medication within a sheath (eg spinal subarachnoid space for narcotic analgesics, local anesthetics
  • allow certain drugs to bypass the blood brain barreir and reach CNS
  • for tendon sheath or bursa to treatment inflammation
22
Q

topical medications

A
  • apply directly to the skin
  • absorbed fairly poorly through the epidermis and into the systemic circulation
  • antibiotics to treat skin infection
  • eyedrops
  • ear drops
  • to mucous membranes (eg nasal mucosa via nasal spray)
23
Q

transdermal

A
  • absorbed through the dermal layers and into the subcutaneous tissues or the peripheral circulation
  • provides a slow and controlled release
  • maintain contant level for prolonged periods of time
  • iontophersis and phonophoresis to treat pain and inflammation
24
Q

bioavailability

A
  • the extent to which the drug reaches the system circulation
  • depends on route of administration and drugs ability to cross membrane barriers
25
Q

membrane structure and function

A
  • lipid domain moves freely on cell membrane
  • lipid soluble compounds (inc most drugs) are able to pass directly through membrane by dissolving in lipid bilayer
  • dynamic ion channels
  • many drugs can affect their ability to open and close to alter cell excitability
26
Q

Passive diffusion

A
  • the driving forces, w/o expending any energy, are the electrical (charged particles), chemical, and pressure differences on the two sides of the membrane
  • rate depends on magnitude of gradient, size of substance, distance and temperature
  • membrane must be permeable to the diffusing substance
  • many drugs are lipid soluble
  • certain nonlipid soluble substances (eg protein) can be encapsulted in lipid vesicles
27
Q

Effect of pH and ionization on absorption

A
  • weak acid drug is in acidic environment it tends to be neutral, nonionized form
  • drugs diffuse more readily through lipid layer if they are in neutral nonionized form
  • a weak base drug is ionzied in acidic envirnment and poorly absorbed (ionization decreases their lipid solubility)
  • when it reaches duodenum same drug becomes nonionzied and lipid soluble, allowing it to be absorbed from the proximal small intestine
28
Q

diffusion trapping

A
  • often desirable for drug to remain ionzied while in urine so that body will excrete drug because if drug becomes nonionized while in nephron, may reabsorb back into body
  • urine can sometimes be acidic and at other times basic, weak acids drugs are trapped in nephron and excreted more readily, but if urine is acidic, weak bases are excreted better
29
Q

diffusion between cell junction

A
  • nonionzing goes through easier than ionzied
  • primary way that drug may diffuse across barrier is by diffusing first into and then out of other side of cell comprising the barrier
30
Q

active transport

A
  • use membrane protein (carrier) to transport substances across cell membrane
  • characteristics: carrier specificity, expenditure of energy (ATP hydrolysis), ability to transport substances against a concentration gradient
31
Q

facilitated diffusion

A
  • features of both active and passive
  • an assited protein carrier is present, no net energy is expended
  • ex: skeletal miscle glucose uptake
  • inability to transport substances uphill against concentration gradient
32
Q

endocytosis vs exocytosis

A

endo: drug is engulfed by cell via an invagination of cell membrane
* allow certain large nonlipid soluble drugs to enter cell
exo: synthezied within cel can be encapsulated in vesicles, merged with inner surface of cell membrane, extruded through membrane and out of cell

33
Q

what is osmosis?

A
  • diffusing substance is water
  • water moves high to low concentration
  • bulk flow
34
Q

what is carrier specificity

A

protein carrier exhibits some degree of specificity for certain substances, usually discirminating among diff. compounds according to their shape and electrical charge

35
Q

what is expentidure of energy

A

the term active transport implies that some energy must be used to fuel the carrier system
energy is usually in form of ATP hydrolysis

36
Q

Factors affecting distribution of drug

A
  • tissue permeability
  • lipid soluble vs non lipid soluble
  • blood flow
    -organs with rich blood flow
  • binding to plasma protein
    -only the unbound drug can reach target tisssue and exert effect
  • binding to subcellular component
  • several drugs bind to organelles cannot be distributed to other components
37
Q

what is ability to transport substances against concentration gradient?

A

carrier mediated active transport carriers substances uphill from areas of low to high concentration

38
Q

adverse consequences of drug storage

A
  • high concetration of drugs, drug metabolites, and toxic compounds stored within tissues can cause local damage
  • drug storage occurs when a reservoir soaks up drug and prevents from reaching target site
  • the drug can leak out of reservoir and reintroduces drug to target site long after original dose should have been eliminated
39
Q

newer techniques for drug delivery

A
  • controlled release preparations: timed: release, sustained release, extended release, or prolonged action preparations
  • implanted drug delivery systems: a small container placed under skin in abdomen that releases a small, measured dose of a drug on a pre programmed schdule
40
Q

targeting drug delivery to specific cells and tissues

A
  • activate the drug only after it reaches specific organ or tissue
  • focus drug effects and reduce its side effects
  • nanotechology
41
Q

nonbiodegradable

A

drug polymer complex is then implanted in body and the drug is slowly released into surrounding tissues

42
Q

biodegradable

A

released as the matrix gradually dissolves

43
Q

what is nanotechnology?

A
  • use of small particles (particles between 1-1000 nm) with physical properties that facilitate drug absorption or distribution within the body
  • these nanoparticles may be able to enhance drug movement across specific membranes
  • could help direct drug to specific type of cell
  • activate the nanoparticle after it reaches certain tissues or even target the drug to specifc subcellular organelles
44
Q
A

Internal Medicine (7 decks)

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