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PoD topics > Drugs 1: Drug Absorption > Flashcards

Drugs 1: Drug Absorption Flashcards

1
Q

What 4 basic factors determine pharmacokinetics?

A

Absorption, Distribution, Metabolism, Elimination

= ADME

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2
Q

What are the main reasons for studying pharmacokinetics? (3)

A
  1. individualise patient therapy
  2. monitor medication with a narrow therapeutic index
  3. decrease the risk of adverse drug reactions while maximising pharmacological response to medication
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3
Q

What are the 8 main ways of administering drugs to enter the bloodstream?

A
  1. oral
  2. intravenous
  3. transdermal
  4. subcutaneous (injection under skin)
  5. nasal
  6. inhalation
  7. other GI (sublingual/under tongue or rectal)
  8. Intramuscular
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4
Q

What is a common condition treated by sublingual drugs? (under the tongue)

A

Angina

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5
Q

What is the definition of absorption?

A

the process of movement of unchanged drug from the site of administration to the systemic circulation.

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6
Q

What is in correlation with a plasma concentration of a drug?

A

Therapeutic response

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7
Q

What are the 2 most important issues to consider when giving an oral drug?

A
  1. amount of drug which enters the systemic circulation

2. speed at which it happens

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8
Q

What is Tmax?

A

Time taken to peak concentration

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9
Q

What is Cmax?

A

Peak concentration

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10
Q

How does a quicker rate of absorption affect Tmax?

A

the earlier the drug concentration peak (Tmax will be reached quicker)

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11
Q

What effect does increasing dosage of a drug have on the Tmax?

A

No effect (it affects the Cmax; concentration of the drug)

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12
Q

What does the area under the curve represent? (the AUC)

A

How much of the drug reaches the systemic circulation over a period of time

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13
Q

What is the therapeutic range?

A

Wide range over which a drug is active in

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14
Q

What will happen if a drug is below and above a therapeutic range?

A

below: NO sufficient or pharmacological action
above: toxicity occurs

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15
Q

What is a therapeutic index?

A

Measure of the range at which the drug is safe and active (works best in the middle region)

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16
Q

What does the AUC allow us to estimate?

A

Allows us to estimate the amount of drug which reaches the circulation and which is available for action(bioavailability)

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17
Q

What is the term which describes what amount of the drug reaches circulation and is available for action?

A

Bioavailability

18
Q

Why do intravenous drugs have very high peak levels?

A

There is 100% guarantee all of the drug will enter the body unlike rectal or oral

19
Q

What 4 factors affect bioavailability? (not including disease state)

A
  1. formulation (drugs)
  2. ability of drug to pass physiological barriers (particle size, lipid solubility, pH and ionisation)
  3. gastrointestinal effects (gut motility, food, illness)
  4. First pass metabolism (how fast the drug is metabolised, if fast then may not reach bloodstream in time)
20
Q

What does dissolution mean?

A

Breakdown of tablet in the stomach

21
Q

What is the main membrane drugs cross in terms of physiological barriers?

A

Small intestine/ bowel

22
Q

What are the 4 possible mechanisms involved in transport across physiological barriers?

A
  1. passive diffusion
  2. bulk flow
  3. filtration
  4. active transport (facilitated diffusion, ion-pair transport, endocytosis)
23
Q

Why do most drugs not completely ionise in water?

A

As they are weak acids and bases

24
Q

Are both ionised and un-ionised forms of drugs present?

A

Yes

25
Q

Do ionised drugs cross cell membranes?

A

NO, ionised drugs do not cross cell membranes

26
Q

Do un-ionised drugs cross cell membranes?

A

Yes- they unionised drugs distribute across the membrane until equilibrium is reached (equal concentration of drug on both sides)

27
Q

Henderson-Hasselbalch equation describes a relationship between which two factors?

A

local pH and degree of ionisation

28
Q

What does Henderson-Hasselbalch equation demonstrate?

A

Small changes in pH may significantly influence the ionisation of a drug (therefore rate of absorption and diffusion)

29
Q

To pass across a lipid layer, what must a drug be? (2)

A
  • in solution

- lipid soluble (have high lipid solubility)

30
Q

What is the term which describes the ratio of the amount of drug which dissolves in the lipid and water phase when they are in contact?

A

Lipid-water partition coefficient

31
Q

What are main properties of passive diffusion in terms of:

  1. conc. gradient
  2. selectivity
  3. saturation
  4. carrier needed
A
  1. moves along concentration gradient (no energy needed)
  2. non-selective
  3. not saturable
  4. no carrier needed
32
Q

What are main properties of active transport in terms of:

  1. conc. gradient
  2. selectivity
  3. saturation
  4. carrier needed
A
  1. moves against concentration gradient ( energy needed)
  2. selective/ specific
  3. saturable
  4. carrier needed (reversible bound)
33
Q

What are main properties of facilitated diffusion in terms of:

  1. conc. gradient
  2. selectivity
  3. saturation
  4. carrier needed
A
  1. moves along the concentration gradient (no energy needed)
  2. selective/ specific
  3. saturable
  4. carriers needed
34
Q

What 2 forces drive filtration/ bulk flow/ pore transport?

A
  • Hydrostatic force

- osmotic pressure difference across the membrane

35
Q

What 3 factors affect gastrointestinal absorption of drugs?

A
  1. gut motility
  2. food
  3. illness (malabsorption)
36
Q

What is first pass metabolism?

A

metabolism of drug prior to reaching the systemic circulation ( affected by enzymes and acid in Gi tract and liver enzymes)

37
Q

Which drug administration method uses first pass metabolism?

A

Oral route

38
Q

what are the main consideration for mode of drug administration? (4)

A
  • purpose and site of drug action
  • patient’s ability to take medicine
  • speed of action needed
  • reliability of absorption
39
Q

What main 3 chemical properties determine absorption at different sites?

A
  • pH
  • lipid solubility
  • ionisation
40
Q

Which administration methods avoid first pass metabolism? (7)

A
  1. subcutaneous
  2. intramuscular
  3. GI administration (sublingual and rectal)
  4. Inhalation
  5. Nasal
  6. Transdermal
  7. intravenous
41
Q

Which administration methods provide instant absorption/ action? (4)

A
  1. intravenous
  2. intramuscular
  3. subcutaneous
  4. Other GI: sublingual
42
Q

Which administration methods might have slow absorption? (5)

A
  1. oral
  2. transdermal
  3. inhalation
  4. nasal
  5. Other GI: rectal

PoD topics (34 decks)

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