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PoD > Drug Absorption > Flashcards

Drug Absorption Flashcards

1
Q

How do drugs achieve effect?

A

Must enter blood and be distributed to site of action

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2
Q

What are the factors that determine drug pharmacokinetics?

A
  • Absorption
  • Distribution
  • Metabolism
  • Elimnation
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3
Q

What is absorption of a drug defined as?

A

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

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4
Q

Issues with absorption

A
  • Amount of drug which enters systemic circulation

- Speed at which this happened (distribution)

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5
Q

What is the Tmax of absorption?

A

Time to reach peak concentration

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6
Q

What is the Cmax?

A

The peak concentration

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7
Q

What is the AUC?

A

Area under the drug conc. time curve representing the amount of drug which reaches systemic circulation

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8
Q

How does rate of absorption affect Tmax?

A

Rapid rate = earlier Cmax is reached

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9
Q

Affect of increasing dose on Tmax and Cmax?

A

Increase dose = no change to Tmax, but increases Cmax

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10
Q

What is the therapeutic range?

A

A measure of the range at which a drug is safe and active

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11
Q

What happens above and below therapeutic range?

A
  • Above: toxicity

- Below: insufficient dose so no action

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12
Q

Define bioavailability

A

Estimate the amount of drug which reaches the circulation and is available for action

IV - 100% bioavailability

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13
Q

Factors affecting bioavailability

A
  • Formulation
  • Ability of drug to pass barriers
  • Gastrointestinal effects
  • First pass metabolism
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14
Q

How does formulation affect bioavailability?

A

Slow release drugs - effects speed at which drug is released

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15
Q

What are characteristics of drug that affects a drug’s ability to pass barriers?

A
  • Particle size
  • Lipid solubility
  • pH and ionisation
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16
Q

Relationship between pH and ionisation of drugs?

A

Henderson-hasselbalch equation: change in pH affects ionisation of drug and therefor rate of absorption or diffusion

17
Q

Can ionised drugs cross membranes?

A

No, only un-ionised drugs distribute across the membrane until equilibrium is reached

18
Q

What is ion trapping?

A

An acidic drug is more concentrated in the compartment with high pH

19
Q

What kind of drugs diffuse across a lipid layer?

A

Be in solution and lipid soluble

20
Q

What is the lipid-water partition coefficient?

A

Ability of a drug to diffuse across a lipid barrier

21
Q

What is required for absorption?

A
  • Energy - occurs against concentration gradient
  • Drug to resemble natural compounds
  • Drug reversibly bound to a carrier
22
Q

What is bulk flow?

A

Movement of drugs across a membrane due to hydrostatic or osmotic pressure differences
-water soluble drugs

23
Q

What factors affect absorption of a drug from the GI tract?

A
  • Motility
  • Food
  • Illness
24
Q

Explain motility of a drug

A

Speed of gastric absorption affects speed that drug reaches site of absorption (small intestine)

25
Q

Explain affect illness on absorption

A
  • Malabsorption affects rate

- Migrained reduces rate of stomach emptying and therefor rate

26
Q

What is First Pass Metabolism?

A

Metabolism of a drug before it reaches systemic circulation

27
Q

How do you get over first pass metabolism?

A
  • Increase dosage
  • IM admin.
  • Sublingual admin.
  • Rectal admin. (slow)
  • Transdermal admin.
28
Q

What are the four primary system that affect first pass metabolism?

A
  • Gut lumen enzymes
  • Gut wall enzymes
  • Hepatic (liver) enzymes
29
Q

FPM effect of bioavailability

A

Decreases bioavailability of drug as metabolised before reaching systemic circulation

30
Q

List the considerations for mode of administration

A
  • Purpose & site of drug action - FPM
  • Disease effects
  • Ability to take meds
  • Speed of action
  • Reliability of absorption

PoD (35 decks)

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