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Pharmacology > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

Pharmacokinetics

A

the relationship between dose regiment and drug concentration

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2
Q

Pharmacodynamics

A

relationship between drug concentration and the theraputic/toxic effetcs

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3
Q

Pharmacokinetic Interactions

A

changes in outcome are the result of changes in relationship between the DOSE and the CONCENTRATION

the pharmacologic effect has changed as a result in a change in the drug concentrations

something is happening a the ADME level

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4
Q

Pharmacodynamic Interaction

A

changes in the OUTCOME are the result of changes in the relationship between the DRUG CONCENTRATION and EFFECT.

the pharmacological effect has changed despite lack of change in drug concentrtion

something is happening as the receptor level

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5
Q

Drug Absorption

A

process of drug moving from site of administration to systemic circ. (bypassed by IV administration)

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6
Q

Cell membranes

A

fxn as barriers to drugs
divide body into compartments
lipid-soluble=move freely across
not lipi-soluble=move less freely acorss

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7
Q

Bioavailability

A

amnt of drug that reaches systemic circ.

expressed as percent or frac. of drug administered which reaches the systemic circ.

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8
Q

AUC

A

area under curve: pharmacokinetic parameter which quantifies drug exposure

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9
Q

Absolute Bioavailability

A

situation when one of the AUC’s being compared is in a dose form with which there is 100% (absolute) absorption (with and IV dose form)

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10
Q

Relative AUC

A

comparing 2 dose forms in terms of relative amounts of drug that reaches systemic circulation

comparing AUC of 1 product RELATIVE to another

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11
Q

Bioavailability depends on

A

absorption characteristics of the drug & dose form

metabolism prior to drug reaching systemic circ (intestinal wall, liver, 1st pass effect)

presence of interacting substances (drugs/food)

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12
Q

Salt form differences

A

when changing from dose forms, have to consider differences in extent of absorption and amnt contained in the formulation

ex:salt forms have less than 100% of drug

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13
Q

Volume of Distribution (Vd) is higher in drugs with

A

HIGHER lipid solubility
lower protein binding
GREATER tissue binding

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14
Q

how would you use Vd to calculate the dose required to achieve target max. concentratipn (cpmax)

A

Cpmax=Dose/Vd
or
Dose=Cpmax x Vd

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15
Q

What can Vd be used for

A

determining drug doses

providing clinician w/sense of the spaces/areas/compartments into which drug distributes

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16
Q

Changes in fluid status would mostly likely affect a drug that has a

A

SMALL Vd (drugs are confined to the central compartment, so more or less fluid there will affect the response of the drug)

17
Q

For a drug to be removed by dialysis, the Vd would be…

A

small Vd

the drug will stay in the central compartment (blood stream) so it will be removed by Hd

18
Q

Two general mechanisms that eliminate drugs

A

Biotransformation (metabolism): drug chemically altered to form a “excretable” metabolite

Excretion: removal of a drug/metabolite from body via organ

19
Q

Biotransformation

A

enzyme in organ modify chemical structure of drug (usually liver)

byproduct is metabolite

metabolite:less/no pharmacological activity (unless prodrug)

20
Q

Mechanisms of Hepatic Biotransformation

A

Phase 1 & Phase 2

21
Q

Phase 1 Reactions

A

introduce functional groups to prepare drugs for phase 2 rxns, occurs in LIVER

Oxidation-mediated by cytocrhome P450 (which are sensitive to induction/inhibition &aging/impairment of liver)-most common phase 1 rxn

Reduction-
Hydrolysis

22
Q

Phase 2 Reactions

A

-drug/metabolite conjugated with glucuronic acid, methyl group, acetyl group, sulfate group

-rxns mediated by transferases (enzymes)
(transferases less sensitive to inhibiton/induction)

-produce less lipophilic (more polar) metabolite

more polar metabolite will stay in central compartment be excreted by kidney

23
Q

Excretion

A

primarily kidney

Nephron-drug is filtered by glomaruluous, pass to renal tubule, and excreted in urine

if less polar, may be reabsorbed from tubule & re-enter systemic ciruc.

24
Q

Drugs whos elimination processes are not easily maximized, elimination rate of the drug increases…..

A

in DIRECT proportion to the serum drug concentration concentration

would have linear pk

25
Q

First order elimination

A

elimination rate of the drug increases in direct proportion to serum drug concentration

would have linear Pk

26
Q

Drugs whos elimination process ARE easily maximized the elimination rate of the drug is…..

A

CONSTANT

27
Q

Zero order Elimination

A

when the elimination of the drug is constant

once you max elimination of drug, the elimination rate doesnt change at higher concentration (the organ cant increase elimination and it stays constatn)

28
Q

In Zero order elimination the serum drug concentration are…..

A

disproprtional to the dose administered.

would have non linear pk

once youre at theraputic level, change in dose causes BIG change in concentration

29
Q

In Zero Order elimination, small increases in dose produce…

A

LARGE increases in serum drug concentration

30
Q

In zero order elimination, the half life is…

A

DEPENDET of drug concentration

higher exposure=longer half life

31
Q

In first order elimination, the half life is…

A

INDEPENDENT of drug concentration

half life is always the same

32
Q

At Steady State, the rate of drug going into a pt…

A

is EQUAL to the rate of drug leaving the pt

33
Q

At Steady State, the amount of drug eliminated over the dosing interval…..

A

is EQUAL to the dose admininstered over this time

34
Q

What happens with regard to drug accumulation during steady state?

A

drug accumulation reaches EQUILIBRIUM

35
Q

Factors that can cause a pt’s drug regime to be knocked out of steady state

A

anything that changes the input or out put

frequency of dosing, change in absorption, change in fluid volume, adding another drug, change in dose interval,

36
Q

Primary determinate of how long it will take for a drug regime to reach steady state

A

the time to reach steady state is dependent on half life

drug w/longer half life will takw longer to reach steady state

drugs with shorter half lives will take less time to get to steady state

37
Q

Drug Clearance

A

Volume of blood that is cleared of drug per/time

38
Q

Elimination Half Life

A

Time it takes for the concentration of drug to be reduced by 1/2

39
Q

How drug clearance & elimination 1/2 life have an effect on dosing regiment

A

A drug with a faster clearance or shorter elimination half life will probably need to be dosed more frequently, and vice versa

Pharmacology (21 decks)

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