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PHAR 230 > M1 Lecture 2: Pharmacokinetics > Flashcards

M1 Lecture 2: Pharmacokinetics Flashcards

1
Q

ADME

A

Absorption: Ingestion → blood
Distribution: Blood → organ tissues
Metabolism: Drug converted into chemical compounds for use
Excretion: Elimination out of the body

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2
Q

common routes of administration

A

orally (most common)
intravenous (straight into the blood, most effective)
injections
sublingual (under tongue)
buccal route (above tongue)
topical (skin, eye, ear drops)
rectal and vaginal

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3
Q

bioavaliability

A

% of drug that reaches systematic circulation

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4
Q

which route of administration skips absorption step

A

IV route

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5
Q

factors affecting drug absorption

A

lipid solubility, pH, transit time, enzymatic and chemical stability, food, dosage form

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6
Q

Lipid soluble drugs…

A

CAN cross cell membranes (bc cell membrane mainly made up of lipids)

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7
Q

Water soluble drugs…

A

CANNOT cross cell membranes

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8
Q

most drugs… (in relation to drug and lipid solubility)

A

weak acids and bases

exist in ionized (charged) (H2O soluble, polar) and unionized (uncharged) (lipid soluble, unpolar) form

degree of ionization depends on…
1. pH of enviro
2. pKa of drug (where 50% is ionized and unionized)

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9
Q

what is aspirin (acetylsalicylic acid)

A

weak acid

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10
Q

noreepinephrine

A

weak base

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11
Q

Drug ph: Weak Acid
ph: Acidic
protons (H+):
drug state:
liquid soluble:
rate of absorption:

A

Drug ph: Weak Acid
ph: Acidic
protons (H+): Excess
drug state: unionized>ionized
liquid soluble: yes
rate of absorption: high

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12
Q

Drug ph: weak acid
ph: basic
protons (H+)
drug state:
liquid soluble:
rate of absorption:

A

Drug ph: weak acid
ph: basic
protons (H+): few
drug state: ionized>unionized
liquid soluble: no
rate of absorption: low

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13
Q

Drug ph: weak base
ph: acidic
protons (H+)
drug state:
liquid soluble:
rate of absorption:

A

Drug ph: weak base
ph: acidic
protons (H+): excess
drug state: ionized>unionized
liquid soluble: no
rate of absorption: low

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14
Q

Drug ph: weak base
ph: basic
protons (H+):
drug state:
liquid soluble:
rate of absorption:

A

Drug ph: weak base
ph: basic
protons (H+): few
drug state: unionized>ionized
liquid soluble: yes
rate of absorption: high

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15
Q

stops of absorption along the GI

A
  1. stomach: drug reaches and disintegrates + dissolves
  2. small intestine: high permeability, large surface area, high blood flow (primary site for drug absorption)
  3. large intestine: low permeability and small surface area, poor site for drug absorption, some drugs are absorbed bc long transit period (24-48hrs)
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16
Q

distribution

A

along concentration gradient between blood and tissue (onset, duration, intensity of action)

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17
Q

physiological factors affecting drug distribution

A
  • blood concentration
  • cardiac output
  • organ vascularity and blood flow
  • capillary permeability
  • tissue perfusion
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18
Q

drug properties affecting drug distribution

A
  • degree of ionization
  • liquid solubility
  • binding to plasma and tissue proteins
  • pH
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19
Q

volume of distribution what is it + what is the eqtn

A

measure of space able to contain drug

Vd = (total amount of drug in body / drug concentration in plasma) L/70kg

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20
Q

4 drug reservoirs

A
  • plasma proteins
  • intracellular space
  • fat
  • bones
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21
Q

Compartment: Total body water
Vd (L/70kg):
Drug:
Ex:

A

Compartment: Total body water
Vd (L/70kg): 42
Drug: small water soluble molecules
Ex: ethanol

22
Q

Compartment: Extracellular water
Vd (L/70kg):
Drug:
Ex:

A

Compartment: Extracellular water
Vd (L/70kg): 14
Drug: large water soluble molecules
Ex: Gentamicin

23
Q

Compartment: Plasma
Vd (L/70kg):
Drug:
Ex:

A

Compartment: Plasma
Vd (L/70kg): 3
Drug: large protein molecules
Ex: antibodies

24
Q

Compartment: Fat
Vd (L/70kg):
Drug:
Ex:

A

Compartment: Fat
Vd (L/70kg): >42
Drug: lipid soluble molecules
Ex: diazepam

25
Q

3 results of metabolism

A
  1. bioactivation
  2. deactivation
  3. detoxification
26
Q

Purpose of metabolism

A
  • increased drug’s water solubility
  • helps elimination
27
Q

sites of drug biotransformation (main one, and subsections)

A
  1. Liver (primary site)
    - high concentration of metabolizing enzymes
    - high blood flow
    - receives blood from GI tract
  2. kidneys, intestine, lungs, skin
28
Q

Phase 1 Reaction of Drug Metabolism Overview

A

reactions add or unmask a functional group

modifies product thru oxidation, hydrolysis, or reduction

Oxidation: give o2 to drug and gain elections
Reduction: give (H) hydrogen or take o2, give electron
Hydrolysis: adds water, ex: carboxyl esterases

29
Q

Phase 1 Reactions: Oxidation Reaction

A
  • add O2/lose an electron
  • main enzyme system for this process is the cytochrome P450 (CYPs) enzyme (REMEMBER CYP 3A4 METABOLIZES MOST DRUGS**)
  • other than that enzyme:
    alcohol + alcohol dehydrogenase = aldehyde
    norepinephrine + monoamine oxidase = inactivation
30
Q

Phase 2 Reaction of Drug Metabolism Overview

A

reactions add a large water soluble component to allow excretion by the kidney

Addition of a water-soluble component to facilitate excretion

Glucuronidation, Sulfation, Glutathione conjugation, Acetylation

31
Q

Phase 2 Reactions: Conjunction Reaction

A

adding a water-soluble moiety to phase 1 product - water soluble - easy to excrete

32
Q

Main Conjunction Reaction: Glucuronidation
(Of phase 2 drug metabolism)
Enzyme:
Added Molecules:

A

Enzyme: UDP-glucuronosyltransferase (UGT)
Added Molecules: Glucoronates

33
Q

Main Conjunction Reaction: Sulfation
(Of phase 2 drug metabolism)
Enzyme:
Added Molecules:

A

Enzyme: Sulfotransferase (SULT)
Added Molecules: Sulfates

34
Q

Main Conjunction Reaction: Glutathione conjugation
(Of phase 2 drug metabolism)
Enzyme:
Added Molecules:

A

Enzyme: Glutathione transferase (GST)
Added Molecules: Glutathiones

35
Q

Main Conjunction Reaction: Acetylation
(Of phase 2 drug metabolism)
Enzyme:
Added Molecules:

A

Enzyme: N-acetyl transferase (NAT)
Added Molecules: Acetates

36
Q

1st pass metabolism

A
  • inactivation of orally administered drugs before reaching the systemic circulation
  • before absorption = intestine
  • after absorption = liver
  • result: decreased amount of active drug reaching blood and site of action
  • how to avoid: change route of administration
37
Q

factors affecting biotransformation: intra-individual differences

A
  • diseases (especially liver)
  • drug-drug interactions (DDI)
  • diet
  • gut microbiota
38
Q

factors affecting biotransformation: inter-individual differences

A
  • age
  • sex
  • genetic factors
39
Q

routes of excretion

A
  • kidney (primary)
  • GI tract
  • lungs
  • bodily fluids (sweat, saliva, milk)

all meds excreted diff

40
Q

renal excretion

A

glomerular function
- filtration (filtrate = plasma - plasma proteins)

tubular function
- reabsorption (water and useful materials - back to blood)
- secretion (waste products - urine)

41
Q

excretion =

A

filtration - reabsorption + secretion

42
Q

drug and renal excretion

A
  • drugs must b water soluble (ionized) to be excreted thru kidney
  • RBF (renal blood flow) = +/- 1200ml (20-25% of CO)
  • GRF (glomerular filtration rate) = 125ml/min (decreased GRF, decreased excretion)
  • active transporters in renal tubule can move drugs from blood - urine - excretion (ex: penicillin)
43
Q

effect of urine pH on drug excretion (for acidic and basic)

A

acidic urine: increased excretion of basic drugs (ex: opioids)

basic urine: increased excretion of acidic drugs (ex: aspirin)

44
Q

what drugs can be reabsorbed back into the blood

A

lipid soluble drugs

45
Q

what happens to penicillin during active secretion?
how can we solve this problem?

A

+/- 80% of penicillin dose is cleared from the body within 3-4 hrs after administration = lower concentration and effect

to solve: combine drug w drug probenecid (competitively blocks penicillin excretion)

46
Q

methods of excretion

A
  1. lack of absorption thru intestine: drugs w low bioavailability, protein-bound drugs in intestine
  2. excretion via bile: excreted by hepatocytes into bile, eliminated thru GI in feces
47
Q

enterohepatic cycle

A

process where drug after being absorbed into bloodstream from GI tract is taken by the liver, and a portion is excreted into small intestine through bile. in small intestine, some drug can be reabsorbed into bloodstream basically recycling it. can prolong a drug’s presence in body and affect its effectiveness or duration.

48
Q

Glucuronidation

A

Adds: Glucuronate
Enzyme: UDP-glucuronosyltransferase

49
Q

Sulfation

A

Adds: Sulfate
Enzyme: Sulfotransferase

50
Q

Glutathione conjugation

A

Adds: Glutathione
Enzyme: Glutathione transferase

51
Q

Acetylation

A

Adds: Acetate
Enzyme: N-acetyl transferase

PHAR 230 (31 decks)

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