- length of desired response - drug effect lasts LONGER than concentration

2.10 pharmacokinetics Flashcards by Adriana Beruvides

four basic pharmacokinetic processes?

ADME
Absorption
Distribution
Metabolism
Excretion

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absorption

process by which drug molecules move from site of administration to circulating fluids

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distribution

process by which drug mol move from circulating fluids to tissue

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metabolism

process by which drug molecules are chemically altered

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excretion

process by which a drug is removed from the body

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what are characteristics of a drug that can affect responses?

molecular size/structural features
degree of ionization
lipid solubility in ionized/unionized forms
protein binding in serum/tissue

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what can affect absorption?

route of administration
chemical form (rate/degree of disintegration and dissolution)
area of absorbing surface
circulation to absorbing site
concentration at absorbing site
pH of site

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bioavailability

fraction of drug that reaches systemic circulation

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what is bioavailability of IV administration?

100%

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onset of action

time required for desired response to begin

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duration of action

length of desired response

- drug effect lasts LONGER than concentration

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theraputic index

quantitative measurement of the relative safety of a drug

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first pass effect

phenomenon in which a drug gets metabolized at a specific location in the body that results in a reduced concentration of the active drug upon reaching its site of action or the systemic circulation
- must go through liver before circulation so it will undergo hepatic metabolism

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_____ and ____ can decrease bioavailability of orally administered drugs

rate of absorption, first pass metabolism

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what can avoid the first pass effect?

sublingual tablets, transdermal, rectal suppositories

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sublingual absorption provides direct access to _____ veins

systemic

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what are the routes of administration? (dont have to know them all, just recognize)

Enteral (oral-po, rectal - pr, sublingual - buccal)
Parenteral (Intravenous, intramuscular- im, subcutaneous- sc, intraperitoneal- ip, etc)
inhalation
topical
transdermal

advantages and disadvantages to oral administration?

ADVANTAGE: most convenient, slow uniform absorption, safe
DIS: destruction of drug by enzymes or pH, drugs can bind to GI contents

advantages and disadvantages to rectal administration?

ADVANTAGES: limited first pass metabolism, useful when you cant use oral route
DISADVANTAGES: absorption often irregular and incomplete, may cause irritation to rectal mucosa

advantages and disadvantages to sublingual administration?

ADVANTAGES: rapid absorption, avoids first pass metabolism
DISADVANTAGES: absorption of only small amounts

4 types of parenteral ROA

intramuscular, subcutaneous, intravenous, intradermal

advantages and disadvantages to IV administration?

ADVANTAGES: most direct, bypass absorption
DISADVANTAGES: increase risk of adverse effects from high con.

advantages and disadvantages to intramuscular administration?

advantages: quick, easy
disadvantages: painful, bleeding, may lead to nerve injury

advantages and disadvantages to subcutaneous administration?

ADVANTAGES: quick and easy, fairly rapid absorption
DISADVANTAGES: painful, large amounts CANNOT be given

advantages and disadvantages to inhalation administration?

ADVANTAGES: rapid absorption, used for gases DISADVANTAGES: variable systemic distribution

advantages and disadvantages to topical administration?

ADVANTAGES: allows local effects and minimum side effects DISADVANTAGES: may irritate surface

3 ways drugs cross cell membranes

1. channels/pores (rare) 2. transport systems (SLC proteins, P-glycoprotein) 3. direct penetration of membrane (typical)

P-glycoprotein

transports drugs out of cells (can be inhibited by grapefruit juice and verapamil)

Polar

no net charge, but charge separation (water) - more readily dissolved in polar solvents - do not dissolve in and CANNOT readily cross cell membranes

nonpolar drugs

readily dissolve in nonpolar solvents (oils) | readily cross cell membranes

Weak acids and weak bases can ONLY cross membranes in their ______ form

Unionized

what is ion trapping?

an unionized drug passes cell membrane, but different pHs on one side of membrane dictates that an amount of the drug will be ionized. once they are ionized they cant pass back over the membrane

if there is inflammation is it easier or harder for a drug to get inside a membrane?

easier! membrane is leaky so it can sneak in

Ka is the dissociation constant, what does a large Ka value indicate?

strong acid

higher pkA = more _____

basic

what does henderson-hasselbalch equation tell us?

drugs degree of ionization depending on the pH of the environment

the lower the pH is (relative to pKa), the greater the _________ will be

fraction of a drug in protonated form

when pK = pH what does that mean?

ratio of ionized to unionized is 50%

what are the ionized/protonated versions of acids and bases?

AH, BH+

pH>pKa = more of ______

unprotonated (nonionized): A-, B