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Pharm > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

Actions of body on drug

A

. Absorption
. Distribution
. Metabolism
. Excretion

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2
Q

Pharmacokinetics

A

. Quantitiative description of time course for absorption, distribution, metabolism., and excretion. Of drugs

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3
Q

Pharmacodynamics

A

Quantitative description of biochemical and physiological effects of drugs and mechanisms underlying effects

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4
Q

For most drugs, the duration of action is related to the time the blood level is above ________

A

the minimal effective concentration

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5
Q

Factors that determine blood levels of drug

A 
. Dose
. Route of administration
. Rate and extent of absorption
. Distribution of tissues (sites of actions/loss)
. Rate and extent of metabolism 
. Rate and extent of excretion
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6
Q

Oral administration

A

,. Most common
. Not appropriate for all drugs
. Slow onset
. Not good if patient unconscious

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7
Q

Parenteral drug administration

A

. IV, IA , subQ
. Rapid onset
. Drug must be water soluble and non irritating
. Invasive procedure

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8
Q

Most common transport of drugs across biological membranes

A

. Passive diffusion

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9
Q

Chemical properties of drug

A

Water solubility
. Lipid solubility
. Stability in stomach

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10
Q

Bioavailability

A

Percentage of an orally ministered drug that reaches the systemic circulation

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11
Q

How blood flow affects drug

A

Highly perfused organs like lungs, heart, liver, and kidneys receive the most drug

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12
Q

Drug binding to plasma proteins characteristics

A

. Albumin most important
. Bound drug can’t distribute to tissues
. Drug interactions mean one drug can displace another from the protein binding sites

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13
Q

Distribution of drugs to liver

A

. Large blood flow
. Site of drug metabolism
. Portal-hepatic circulation where drug undergoes first pass metabolism
. Major site for metabolism

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14
Q

Distribution of drugs to kidney

A

. High blood flow

. Site of excretion for many drugs and metabolites

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15
Q

Distribution of drugs to fat

A

. Low blood flow
. Slow accumulation of lipid soluble drugs
. Site of loss
. Redistribution of drugs from other sites

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16
Q

Distribution of drugs to brain

A

. BBB

. Small lipid soluble drugs can cross

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17
Q

Distribution of drugs to fetus

A

Placental barrier is not strong barrier and many drugs can cross

18
Q

Volume of distribution

A

. Measure of how drug is distributed in the body
. Volume in which a drug would have to be dissolved in order to account for all of the drug at the concentration present in the plasma
. Vd=amount of drug in body/Cpss
. Amount of drug in body is equal to the dose if drug is given via IV
. High number means more drug in tissues
. Lower number means drug is mostly in plasma

19
Q

Typical volumes of body water compartments

A

. Total water = 40-45L
. Extracellular = 12-16L
. Blood 5-6L
. Plasma = 2.5-3.0L

20
Q

Ways of terminating drug action

A

. Excrete drug from body
. Metabolize drug to inactive form
. Most effective and most common = metabolism and excretion

21
Q

Types of metabolism reactions

A 
. Microsomal oxidation
. Non-microsomal oxidation
. Reductions
. Hydrolysis
. Conjugations
22
Q

Microsomal oxidation

A

. Main route for many drugs
. Micro some pinched off pieces of smooth ER formed during homogenization
. Contain a family of enzymes and cytochromes that can oxidize drugs (mixed function oxidase or cytochrome isozymes)
. Highest conc. In liver
. Induction and inhibition by drugs
, potential for drug rxns
. Effects caused by altered hepatic function
. Occasionally can form toxic metabolites

23
Q

Examples of rxns catalyzed by mixed function oxidase

A 
. Side chain oxidation 
. Hydroxylation
. N-oxidation
. Sulfoxidation 
. N-dealkylation
24
Q

Conjugation rxns

A

. Phase II reactions
. Involve the coupling of drug or metabolites to small polar molecules
. Glucuronide conjugation
. Sulfate conjugation

25
Q

Kinetics of drug metabolism

A

. Most drugs first order where rate of metabolism spends on concentration of the drug in blood
. Zero order means rate of metabolism doesn’t depend on conc. Of blood

26
Q

Factors affecting drug metabolism

A 
. Age
. Disease
. Nutrition
. Genetic factors 
. Other drugs
. Duration of treatment
27
Q

Filtration of drugs

A

. Low molecular weight drugs are readily filtered
. Drug bound to plasma protein is not excreted
. Alterations in GFR Cana defect the rate of drug excretion

28
Q

Tubular secretion of drugs

A

. Active process
. System for organic acids
. System for organic bases
. Competition of drugs for transport systems

29
Q

Reabsorption of drugs

A

. Passive diffusion
. Lipophilic drugs reabsorbed
. Hydrophilic or ionized drugs remain in tubule and be excreted
. Acidic urine favors excretion of basic drugs whereas basic urine favors the excretion of acidic drugs

30
Q

Clearance

A

. Clearance = rate of elimination/Cp
. Cp is conc, of drug in plasma
. Describes volume of plasma that is cleared of drug in a unit time

31
Q

First order elimination

A

. Rate of elimination depends on conc. Of drug that is present
. Exponential relationship
. Fixed half life

32
Q

Characteristics of zero order kinetics

A

. rate of metabolism is constant and does not depend on conc. Of drug
. Linear relationship
. No fixed half life

33
Q

Time for onset of action in drug

A

. Time between administration and first measurable response

34
Q

Tome to peak effect for drug

A

. Time needed to reach max effect

35
Q

Duration of action

A

. Time from first measurable effect to time when effect is no longer measurable

36
Q

Alpha and beta phase of drug decline in blood

A

. Alpha : rapid decline in conc. From drug moving into tissues
. Beta: metabolism and excretion of drug phase, slower decline than alpha phase

37
Q

Plateau principle

A

All drugs at any dosage will reach a steady state blood level after 4-5 half lives

38
Q

Peak/trough values will decrease if _________

A

. Drug is administered at dosage intervals that are much shorter than the T 1/2 for elimination of the drug

39
Q

Estimation of half lives

A

T1/2= (0.963)(Vd)/CLp
. Vd is volume of distribution
. CLp is clearance from plasma

40
Q

Loading dose calculation

A

Loading dose = target Cp x Vd/F
. Cp is desired plasma conc.
. Vd is volume of distribution
. F fractional bioavailability

41
Q

Calculation of maintenance dose

A

. Dosing rate= target Cpss x CLp/F
. Cpss is steady state conc. In plasma
. CL is rare if clearance
. F is fractional bioavailability ( 1 if dose if through IV)

42
Q

Estimation of drug clearance

A 
. CLp= F x dose per unit time/Css
. CLp = (0.693)(Vd)/ T1/2 patient 
. F is bioavailability 
. CSS is steady state conc. In patient 
. T 1/2 patient is the elimination of half life for drug in patient

Pharm (2 decks)

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