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SBL (Skin, Blood, Lymph) Exam 1 and 2 > Lecture 2: Pharmacokinetics > Flashcards

Lecture 2: Pharmacokinetics Flashcards

1
Q

What is the ADME pneumonic for Pharmacokinetics?

A

A - absorption (oral/GI, inhalation, injection)

D - distribution

M - metabolism (liver - bile or kidney - urine)

E - excretion

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2
Q

What are the 3 main Enteral routes of drug administration?

A
  1. Oral (most convenient, slow and uniform)
  2. Rectal (when oral route precluded)
    • limited first-pass metabolism; irregular absorption
  3. Sublingual (rapid, no first-pass metabolism)
    • can only absorb small amounts
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3
Q

What is are key differences between Intravenous and Intramuscular drug administation?

A

Intravenous

  • most direct route that skips barriers
  • NOT suitable for oily substances
  • inc. risk of adverse effects immediately after inject

Intramuscular

  • suitable for oily substances
  • can lead to nerve injury
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4
Q

What is a key advantage and disadvantage of Subcutaneous drug injections?

A

its suitable for suspensions and pellets but large amounts cannot be given

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5
Q

What is the most common method for drugs to be transported across the lipid bilayer?

A

Simple DIffusion

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6
Q

What is a major transporter of drugs OUT of the cell?

A

P-glycoprotein 1

  • active transport pump that requires energy
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7
Q

When can weak acids and bases move across cell membranes?

A

only when they are in their unionized forms

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8
Q

What is the equation for Bioavailability (F) of a drug?

A

F = AUC (route used) / AUC (intravenous)

F = fraction of drug that reaches blood stream
- is < 1
AUC = area under curve

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9
Q

What is the equation for Concentration in Plasma (Cp) of a drug?

A

Cp = (S x F x Dose) / Vd

S = "salt factor" (less than or equal to 1)
F = bioavailability
Vd = volume of distribution

S and F should be 1 if not provided in question

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10
Q

What is the equation for Volume of Distribution (Vd) of a drug?

A

Vd = amount of drug in body / plasma concentration

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11
Q

How do you calculate Total Body Water for lean males and females?

A

Lean males = 60% of their bodyweight (kg)

Lean females = 55% of their bodyweight (kg)

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12
Q

What do you calculate Extracellular Volume and Plasma Volume?

A

ECV = 1/3 x TBW

Plasma volume = 25% x ECV

ECV = plasma volume + interstitial volume

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13
Q

What is the only condition in which polar or ionized drugs can move across the BBB (and placenta)?

A

they can only move across the membrane barriers if their is a TRANSPORTER for them

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14
Q

What are 4 classic examples of inducers that increase the metabolism of drugs? (PCEC)

A

Phenobarbital, Carbamazepine, Ethanol, Cigarette smoke

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15
Q

What are 4 classic examples of inhibitors that decrease the metabolism of drugs? (EKMG)

A

Erythromycin, Ketoconazole, Metronidazole, Grapefruit Juice

grapefruit juice is a CYP3A4 enzyme inhibitor

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16
Q

What does Phase II Conjugation do to drugs and what two processes does it use to achieve this?

A
  • makes drugs MORE water soluble and MORE excretable (adds highly polar molecule)
  1. Glucuronidation
    • in endoplasmic reticulum and is inducible
  2. Sulfation
    • in cytoplasm
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17
Q

What does Phase II Acetylation and Methylation do to drugs?

A
  • makes drugs LESS water soluble

- transferases tend to reduce drug activity which can inactivate the drug

18
Q

What are 4 non-renal routs of drug excretion?

A

bile, sweat, breath, and breast milk

19
Q

What are 3 major factors that modify renal drug excretion?

A
  1. pH-dependent ionization
  2. competition for active tubular transport
  3. age (GFR falls as we age)
20
Q

What is the difference between Excretion Rate and Clearance, and how do these relate to first order kinetics?

A

ER = mass eliminated per unit time
- inc. as plasma conc. increases

CR = plasma vol. from which all of the solute is removed per unit time (ml/min or FLOW RATE)
- remains constant as plasma concentration changes

21
Q

What is the equation for estimated GFR?

A

eGFR = ((140-age) x (body weight (kg))) / (72 x serum creatinine)

multiply by 0.85 if female

22
Q

What are 3 common drug types that are commonly seen in drug allergies or hypersensitivities? (PAS)

A

penicillin (most serious reactions)

also aspirin and sulfonamides

23
Q

What drug causes problems for individuals that lack plasma esterase?

A

Succinylcholine

  • causes long duration apnea
24
Q

What drugs cause problems for individuals that lack NADH methemoglobin reductase? (NSP)

A

nitrites, sulfonamides, primaquine

  • causes hereditary methemoglobinermia
25
Q

What drug causes problems for individuals that lack liver acetyl transferase?

A

Isoniazid

  • causes inc. toxicity from drugs
26
Q

What drug causes problems for individuals that lack G6P dehydrogenase?

A

Primaquine (dec. GSH)

  • causes drug-induced hemolytic anemia (favism)
27
Q

What drugs cause problems for individuals with porphobilinogen deaminase deficiency? (BESC)

A

barbiturates, estrogens, sulfonamides, chloroquine

  • acute intermittent porphyria
28
Q

What are 3 things you must see that identifies a drug as a teratogen?

A
  1. characteristic malformations
  2. drug given during specific window of vulnerability
  3. incidence inc. with dose and duration of exposure
29
Q

Diethylstibesterol (DES) and Drug-induced Carcinogenesis

A
  • drug originally used to prevent spontaneous abortion in high-risk pregnancies, but later found that daughters exposed in utero had a high incidence of vaginal and uterine cancers
30
Q

What is absorption, distribution, hepatic metabolism, and renal excretion like for neonates and infants?

A

A - inc/dec from GI tract, dec/erratic from IM injection
D - low albumin, BBB no fully developed
HM - decreased
RE - decreased

31
Q

What is absorption, distribution, hepatic metabolism, and renal excretion like for children > 1 yr old?

A

A, D, RE similar to that of adults

HM - much faster than adults but declines from peak at 2 years old

32
Q

What is absorption, distribution, hepatic metabolism, and renal excretion like for geriatrics?

A

A - no change, dec. from GI tract
D - plasma albumin falls, influence by body composition
HM - decreases but widely variable
RE - decreases progressively

33
Q

What are Zero Order Kinetics for drugs?

A
  • a constant amount is eliminated per unit
  • elimination process is saturated
  • amount of eliminated drug independent of drug concentration
34
Q

What is an example of a drug that abides by Zero Order Kinetics?

A

ethanol

  • rate of metabolism is rapidly saturated, so it is basically first order
35
Q

What are First Order Kinetics for drugs?

A
  • constant fraction is eliminated per unit of time
  • elimination process is NOT saturated
  • mass of drug eliminated is directly related to the drug concentration
36
Q

How much of a drug is eliminated in 5 half-lives if it follows first-order kinetics?

A

97%

each half-life BACKWARDS doubles the concentration, while each half-life FORWARDS halves the concentration

37
Q

What is the equation for the First Order Elimination Rate Constant Kel?

A

Kel = Cl / Vd

Cl = clearance (volume drug is eliminated from / time)
Vd = apparent volume of distribution
38
Q

What is the equation for Clearance?

A

Cl = (S x F x (Dose/interval)) / Cp

S = salt factor
F = bioavailability
Cp = plasma concentration
39
Q

What is the equation for Rate of Elimination?

A

RE = (Vmax x C) / (Km + C)

Vmax = max elimination capacity
C = plasma concentration
Km = drug conc. at which elimination rate is 50% of Vmax
40
Q

What is the equation for the Mean Plasma Concentration at Steady State (Cpss)?

A

Cpss = (1.44 x S x F x D x t1/2) / (interval x Vd)

41
Q

What is a loading dose?

A
  • dose needed to rapidly achieve therapeutic drug concentrations for drugs with a very long half-life
42
Q

What is the equation for Loading Dose?

A

LD = Cpss x Vd / (S x F)

S and F = 1 unless otherwise stated in equation

SBL (Skin, Blood, Lymph) Exam 1 and 2 (22 decks)

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