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1. Pharmacology > Pharmacokinetics Absorption > Flashcards

Pharmacokinetics Absorption Flashcards

(57 cards)

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1
Q

Pharmacokinetics

A

Passage of drugs across the cell membrane
Drug movement in the body: Absorption, distribution, metabolism, and excretion (ADME)

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2
Q

Pharmacodynamics

A

What the drugs do to the body (therapeutic effects)

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3
Q

Absorption

A

Process where drugs enter the blood stream without being chemically altered
OR
Movement of a drug from its site of application into the blood

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4
Q

Increased drug concentration and drug action…

A

Increases absorption and distribution

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5
Q

Decreased drug concentration and drug action…

A

Decreases metabolism and excretion

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6
Q

Factors that influence absorption rate

A
  1. Types of transport
  2. Routes of administration
  3. Physiochemical properties of the drug
  4. Concentration of the drug
  5. Protein binding
  6. Dosage forms
  7. Circulation at the site of absorption
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7
Q

Passive diffusion

A

Continues till equilibrium is attained on either side of the membrane

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8
Q

What is passive diffusion dependent on?

A

Concentration gradient
Drug molecular size
Lipophilic nature of the molecule
Temperature
Thickness of the membrane

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9
Q

Lipophilic gradient and passive diffusion

A

Higher the lipid solubility, higher the diffusion

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10
Q

Temperature and passive diffusion

A

Lower the temperature, slower the diffusion

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11
Q

Enteral administration

A

Through GI tract
Oral: min to hrs
Sublingual/ buccal: 3-5 minutes
Rectal: 5-30 min

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12
Q

Parenteral administration

A

Through injection
IV: 100% F, 30-60 sec
IM: 10-20 min
SubQ: 15-30 minutes

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13
Q

Dermal administration

A

Epidermic, installation and irrgation

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14
Q

Inhalation administration

A

Vaporization, gas inhalation, nedbulization

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15
Q

Transdermal administration

A

Patch, microneedle

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16
Q

Major factors in small intestine diff species that effect absorption

A

pH
Epithelial surface
Surface area
Motility
Efflux proteins: P-glycoprotein (takes drug out of cell)

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17
Q

_______ and _________ are rapidly and efficiently absorbed

A

Lipid soluble and Unionized drugs

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18
Q

Water parturition coefficient (PC)

A

High PC= more absorption
(higher lipid to water= more absorption)

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19
Q

What solution causes drugs to be absorbed rapidly?

A

Drugs in aqueous solutions

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20
Q

Rate of absorption

A

solutions –> emulsions –> suspensions –> capsules –> tablets –> sustained release products

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21
Q

What drugs cross the capillary membrane?

A

Drugs with molecular weight less than 50-600 Da

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21
Q

What drugs enter the cell via aqueous filled channels?

A

Small, water-soluble molecules and ions below 50 Da

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22
Q

What happens when the ph and pKa are equal

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A

50% of drug ionised and 50% unionised

23
Q

What happens when pH is one unit below the pKa?

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A

Acid is 9% ionized and base is 91% ionized

24
What happens when pH is 2 units below pKa?
Acid becomes 1% ionized and base becomes 99% ionized
25
What is an exception to the pH and pKa rules?
Strong acids and strong bases remain ionized at all body pH Weak acids and bases are unionized
26
pH- partition hypothesis
Basic drugs in the blood (pH 7.4) readily enter into acidic tissues and fluids Acidic in acidic medium: unionized
27
Ion trapping
Ionized drug gets trapped on one side of a membrane that divides 2 compartments that contains fluids of different pH values
28
When would ion trapping occur
When a drug found in low concentration in the blood (pH7.4) is found in a higher concentration in the urine (pH5)
29
Why does ion trapping occur?
Because only unionized, hydrophobic, uncharged, lipid soluble drugs can pass through cell membranes
30
Example of ion trapping
Weak organic base diffused passively from blood (pH- 7.4) to rumen fluid (pH5.5) --> once passing, base drugs in acids become ionized (broken down, bad) --> ion trapping because they cannot pass the membrane --> cycle of reabsorption and not being excreted --> overdose
31
Where will acidic drugs be more absorbed?
Stomach because stomach is more acidic (like/like= unionized= more absorption)
32
In the intestine (pH 7.8), which will be better absorbed, a weak acid or a weak base?
Weak base because base/base = unionized and better absorption
33
If we alkalinize the urine of 7.8, will a lower or higher percentage of a weak acid be ionized, compared when the urine pH was 6.0?
Higher percentage because a weak acid is ionized in the basic solution
34
Other factors influencing absorption
1. Blood circulation at site (increase blood flow= increased absorption 2. Absorption surface area 3. GIT functional integrity
35
GIT functional integrity
An increase in gastric emptying time, the drug absorption will be more ex: diarrhea drug absorption is reduced due to increased peristaltic activity
36
Bioavailability (F)
The % or fraction of administered drug by any route that reaches circulation in a chemically unchanged form
37
Which route should have 100% bioavailability?
Intravenous route because it's put directly into circulation
38
Oral bioavailability
F=60%
39
How is bioavailability described?
1. Cmax (peak plasma concentration) 2. Time to reach Cmax 3. AUC
40
Bioavailability equation
F= (AUC)oral / (AUC) iv
41
Bioavailability equation with different doses
F= 100 ( ( AUC po x Div) / (AUC iv x Dpo) )
42
What factors affect bioavailability?
First pass effect Gastric emptying Drug solubility/ dissolution (salt forms will increase dissolution) Drug stability in GI fluids
43
First-Pass metabolism
Increased FPM will decrease F Absorbed drug moves via protal circulation to liver High extracted drug may be removed with "first pass" Should give these drugs via IV not orally
44
Which drugs have extensive first pass effect?
Morphine Propanolol Buprenorphine Diazepam Midazolam Pethidine
45
Efflux proteins or transporters
Move drugs and other chemicals out of the cell Normal protective mechanism Important for drug resistance (brain)
46
Distribution
Process where drug reversibly leave the blood stream and enter the extravascular fluid and tissue Determines the transport of drugs to their site of action
47
Highly perfused organs
Liver, kidney, GI tract, brain, lungs Receive rapidly high levels of drug
48
Less perfused organs
Muscle, bones, fat tissue
49
Plasma-protein binding
Reduces efficiency of drug distribution PP bound drugs non-diffusible
50
Plasma protein bound drugs
Pharmacologically inactive and less efficacious and potent Don't undergo metabolism and excretion via glomerular (limits filtration) Long plasma half-lives Narrow therapeutic index and small volume of distribution
51
What are acidic and basic drugs bound to?
Acidic: albumin Basic: a1-acid glyco protein
52
What does drug binding do?
Slows the rate where the drug reaches a concentration sufficient to produce a pharmacologic effect
53
Blood brain barrier
Formed by endothelial cells Doesn't permit ionized and non-lipid soluble drugs TJs!!!!
54
Placenta
Highly ionized drugs and drugs with low lipid solubility excluded Tetragenic drugs (causing birth defects) blocked
55
Milk
Mammary gland- lipid barrier and many drugs readily diffuse from plasma into milk Max residue levels in milk
56
Volume of distribution (Vd)
Dose / plasma concentration Decreased by plasma protein binding Increased by tissue binding

1. Pharmacology (29 decks)

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