introduction to pharmacology Flashcards

1
Q

pharmacokinetics

A

the study of drug movement through the body or “what the body does to the drug”. how does a drug reach the sites of action within the body?

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2
Q

the four pharmacokinetic processes

A

ADME: administration/absorption, distribution, metabolism, excretion

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3
Q

drug absoprtion

A

time from administration to entrance into the bloodstream. onset of action is largely determined by rate of absorption, intensity of effect determined by the extent of absorption, bioavailability

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4
Q

bioavailability

A

the percent of dose that enters blood: IV is 100%, and PO is less than 100%

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5
Q

absorption

A

extent of movement depends on the ability of drugs to pass to and from the major spaces of the body: intracellular, intravascular, and interstitial. diffusion of a molecule from area of high to low concentration. in many cases, drugs can pass freely between wide junctions, or gaps, in a capillary wall

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6
Q

absorption pt 2

A

at other times drugs must pass across membranes via: channels or pores, transport systems, or direct membrane penetration (for direct penetration, drug must be lipid soluble, nonpolar, or nonionized

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7
Q

pH partitioning (ion trapping)

A

stomach acid ph is 2, blood stream pH is 7.38

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8
Q

mechanisms of drug transport

A

passive diffusion (lipophilic, small size), active transport (electrolytes), carrier proteins (structurally selective, hormones), endocytosis (immune complexes)

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9
Q

drug absorption facts

A

liquids absorb faster than pills. food in the stomach impairs absorption. most absorption occurs in the duodenum, IM/SC administration results in faster absorption. skin, mucus membranes and lungs serve as additional sites of absorption.

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10
Q

routes of administration: parenteral

A

the space between the enteric canal and the surface of the body (outside of the GI tract). EX: intravenous (IV), intramuscular (IM), subcutaneous (sub Q)

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11
Q

routes of administration: enteral

A

using the GI tract

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12
Q

intravenous (IV): barriers to absorption

A

none

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13
Q

intravenous: patters of absorption

A

direct

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14
Q

intravenous: advantages

A

rapid onset, control of level of drug, ability to administer large volumes of fluid

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15
Q

intravenous: disadvantages

A

expensive, inconvenient, cannot take it back, infection, fluid overload, embolism

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16
Q

intramuscular and subcutaneous: barriers to absorption

A

none easily passes through spaces of capillary wall

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17
Q

intramuscular and subcutaneous: patterns of absorption

A

rapid or slow, water solubility of the drug, blood flow to the site of injection

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18
Q

intramuscular and subcutaneous: advantages

A

good for meds with poor water solubility, used for administration of depot preparations

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19
Q

intramuscular and subcutaneous: disadvantages

A

discomfort, inconvenient, can be painful, infection, nerve damage

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20
Q

oral (PO): advantages

A

easy, convenient, safe

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21
Q

oral: barriers to absoprtion

A

requires patient cooperation, epithelial cells line the GI tract

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22
Q

oral: patterns of absorption are highly variable

A

solubility/stability of the drug, gastric and intestinal pH, gastric emptying time, presence of food, co-administration of other drugs, coatings on the drugs

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23
Q

additional routes of administration

A

topical: transdermal, sublingual
inhalation
suppository
direct injection to the site of action

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24
Q

factors affective absorption

A

route
formulation: dyes, binders, coatings; solubilizers, liposomal preparation
particle size
acid base properties
temperature
blood flow

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25
Q

what is distribution?

A

the movement of drugs throughout the body. carried by blood to site of action (dependent on blood flow), vascularity aids it, move between capillary cells, aided by plasma binding proteins, tissue deposits may result

26
Q

distribution: entering cells

A

some drugs must enter cells to reach their sites of action, and most must enter to undergo metabolism and excretion: lipid solubility and transport system

27
Q

distribution: exiting the vascular system

A

capillary beds, blood brain barrier (tight junctions, not fully developed in infants), placental drug transfer (not an absolute barrier), protein binding (plasma albumin, drugs can form reversible bonds, bound molecules cannot reach their sites of action, metabolism, or excretion, drugs w ability to bind to albumin will compete for sites and displace other drugs causing increased levels of free drug)

28
Q

plasma binding proteins

A

albumin-most abundant, low affinity, least selective
globulin-low concentration, high affinity, selective binding to sex steroids
alpha 1 glycoproteins
lipoproteins

29
Q

plasma binding proteins

A

-only free drug is active
-bound drug is inactive bc of the large size (drug reservoir, released as free drug is utilized)
-bound drugs have a longer half-life (epinephrine 0% bound. T 1/2 = 15 sec, T 1/2 is 6 hours)

30
Q

plasma binding proteins

A

-binding can result in drug interactions (warfarin 99% bound, aspirin 50% bound)
-low PBP can increase free drug leading to toxicity (malnutrition, liver disease, kidney disease)

31
Q

consequences of tissue deposits: drug reservoir

A

anabolic steroids detected long after last dose

32
Q

consequences of tissue deposits: lipid soluble drugs

A

lipid soluble drugs can cause toxicity if rapid weight loss occurs

33
Q

consequences of tissue deposits: loading dose

A

some drugs may need loading dose to saturate tissue deposits and establish MEC: then maintenance dose for stable MEC, procainamide, voriconazole

34
Q

consequences of tissue deposits: potential site for drug interactions

A

e.g. quinidine displaces digoxin from muscle deposits leading to digitoxicity

35
Q

barriers to distribution

A

blood brain barrier, blood testes barrier, placental barrier (most drugs cross placenta, many can enter breast milk as well)

36
Q

metabolism

A

main site of metabolism is the liver (cytochrome P450 system)

37
Q

biotransformation

A

the chemical alteration of drug structure

38
Q

metabolism special considerations: first pass effect

A

rapid inactivation of some oral drugs as they pass through the liver after being absorbed. parenteral administration will by pass this effect

39
Q

metabolism special considerations: nutritional status

A

adequate nutritional status provides the required cofactors for the hepatic drug metabolizing enzymes to function

40
Q

metabolism special considerations: competition between drugs

A

two or more drugs that use the same metabolic pathway may cause a decrease in metabolism of one or more

41
Q

special considerations: age

A

infants: liver is not fully developed

42
Q

special considerations: induction of drug metabolizing enzymes

A

some drugs can cause the liver to synthesize more drug metabolizing enzymes. increases metabolism of the drug and other drugs

43
Q

special consideration: inhibition of drug metabolizing enzymes

A

decrease rates of drug metabolism

44
Q

prodrug

A

a biologically inactive compound which can be metabolized in the body to produce a drug (codeine turns into morphine once metabolized. once delivered, it becomes active and works)

45
Q

metabolism: therapeutic consequences

A

-accelerated renal excretion
-drug inactivation
-increased therapeutic action
-activation of prodrugs
-increased toxicity
-decreased toxicity

46
Q

excretion

A

the removal of drugs from the body
renal drug excretion: glomerular filtration, passive tubular reabsorption, active tubular secretion

47
Q

factors that modify renal drug excretion

A

-pH dependent ionization
-competition for active tubular transport

48
Q

non-renal routes of drug excretion

A

breast milk, bile (stool), lungs (exhalation), sweat and saliva

49
Q

time course of drug response

A

serum/plasma drug levels: drug levels are highly predictive of therapeutic and toxic responses

50
Q

minimum effective concentration (MEC)

A

the minimum plasma drug level which therapeutic effects will occur

51
Q

toxic concentration

A

the level at which toxic effects occur

52
Q

therapeutic range

A

falls between the MEC and toxic concentration. enough drug is present to produce a therapeutic response.

53
Q

therapeutic range: narrow vs wide

A

half life is a lot faster (metabolized faster)

54
Q

drug half life

A

the time required for the amount of drug in the body to be decreased by half

55
Q

plateau

A

-when a steady level of drug has been achieved
-when the amount of drug eliminated between doses equals the dose administered
-it takes four to five half-lives to achieve plateau

56
Q

why does drug plateau matter?

A

determines dosing

57
Q

reducing fluctuations in drug levels

A

administer a continuous infusion
administer a depot preparation
reduce the size of a dose and the dosing interval

58
Q

onset of action

A

time from when drug is administered to when it reaches minimum effective concentration. how long it takes to start to have an effect

59
Q

duration of action

A

time from when drug first reaches minimum effective concentration to when it falls below the minimum effective concentration. how long does the effect last

60
Q

peak and trough

A

peak: the highest blood level of drug
trough: the lowest blood level of drug. for trough lab, draw serum level immediately before administration of next dose