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Pharmacology > Drug Movement In Body > Flashcards

Drug Movement In Body Flashcards

1
Q

What is the dist stage

A

Process drug leaves the site of admin, enters the blood and subsequently the tissues perfused by the blood
Once within a tissue further blood indept dist, dictated by a conc grad may occur by diff

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2
Q

What is the metab of drug

A

Process which tissue enzymes principally in liver catalyse chem conv of a freuquently lipid sol drug to often less active and more polar form that is readily excreted

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3
Q

What’s the excretion part

A

Process remove the drug or its metabolites form the body

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4
Q

What are the steps of drug disposition

A

Abs
Dist
Metab
Excretion

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5
Q

What are some physicochemical factors controlling drug abs

A

Solubility - drug must dissolve in order to be abs

Chem stability - destroyed in stomach acid or enzymes in GI tract

Lipid to water coeff - abs usually by simple diffusion across mem

Degree of ionisation - only unionised forms readily diffuse across lipid bilayer unaided

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6
Q

What does the degree of ionisation depend on

A

PKa of drug and local pH
PKa = pH which drug half ionised and unionised
Use Henderson hasselbach eqn

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7
Q

What is the Henderson hasselbach eqn

A

For acid - pH - pKa = log(a/ah)
Same for base

As pH increases for an acid the percentage of drug which is ionised is decreased

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8
Q

What is abs of weak acids facilitated by

A

By the acidic pH of stomach lumen

Bases not abs In stomach but in small intestine

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9
Q

Acidic drugs become less ionised when

A

In an avid enviro such as stomach whilst basic drugs become less ionised in basic enviro

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10
Q

What are some factors affecting GI abs

A

GI motility - empty and move thro intestines, mod by drugs and food

PH at abs site

Blood flow to dormancy and int which is increased by food

Way Drug manufactured to release at so rates/sites

Physicochemical interactions

Presence of transporters in mem of epi cells ehci can facilitate Drug abs

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11
Q

What is oral availability

A

Fraction of drug that reaches the systemic circ after oral ingestion

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12
Q

What is systemic availability

A

Fraction that reaches systemic Circulation after abs admin via IV

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13
Q

What can happen to orally admin drugs

A

Become inactivated by enzymes in gut wall and liver before each systemic circ and body tissues

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14
Q

What are some common routes of drug admin

A 
Oral 
Inhalation 
Recital 
IV 
Subcutaneous 
Buccal 
Intramuscular 
Topical
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15
Q

What are the ads and disads for oral admin

A

Ads

  • simple
  • convenient
  • non sterile
  • good abs for most drugs

Disads

  • inactivatin by enzymes or acids
  • food binding
  • first pass metab
  • swallowing
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16
Q

What are the ads and disads for sublingual/ buccal admin

A

Ads

  • rapid abs
  • by pass portal system
  • avoids gastric acid

Disads

  • infrequnet route
  • few available
17
Q

What are the ads and disads of rectal admin

A

Ads

  • rapid abs
  • used for nocturnal use
  • when oral route compromised

Disads

  • infrequent
  • vary abs
  • aesthetically distasteful
18
Q

What is an enteral drug

A

Admin via GI tract

Oral
Sublingual/ buccal
Rectal

19
Q

What are the ads and disads of IV admin

A

Ads

  • rapid onset
  • continuous infusion

Disads

  • steril prep
  • risk of sepsis or embolism
  • high drug levels at heart
20
Q

What are the ads and disads for intramuscular admin

A

Ads

  • rapid onset for lipid sol drugs
  • slow prolonged release

Disads

  • painful
  • tissue damage
  • abs vary
  • dept on muscle blood flow
21
Q

What are the ads and disads of subcutaneous admin

A

Ads
- ideal for drugs reuniting parenteral admin (peptides)

Disads
- few disads

22
Q

What are the ads and disads of inhalation admin

A

Ads

  • lungs large sa
  • good for volatile agents
  • ideal for local effect

Disads
- requires degree of manual dexterity

23
Q

What are the ads and disads of transdermal admin

A

Ads
- slow abs across skin to circ can prod a smooth plasma conc

Disads

  • suitable for few drugs
  • local irritation possible
24
Q

What are the ads and disads of topical admin

A

Ads
- ideals for local effect

Disads
- few disads

25
Q

What is a parenteral drug

A

Drug takes a route that is not via GI tract

26
Q

What is drug dist

A

Drugs within systemic circ can be dist to one or more body fluid compartments

27
Q

How can drugs be distributed

A

Bound or free forms in each compartment
Only free drugs can move between compartments

  • ionised and unionised drugs that are not bound to plasma protien can move freely by diffusion
  • only unionised drugs readily move by diffusion
28
Q

What are some body compartments

A

Plasma water
Fat
Trans cellular water
Intracellular water

Interstitial water

29
Q

What sit he apparent volume of a drug

A

Drugs not evenly dist so apparent vol is vol of drug that is dissolved vol of dist

30
Q

What is the volume of distribution

A

Amount of drug in body/plasma concentration

31
Q

A volume of distribution less than 10L implies

A

Drug is largely retained in the vascular compartment

32
Q

A volume of dist between 10-30L suggests

A

Drug is largely restricted to extracellular water as low lipid solubility of drug

33
Q

A volume dist of greater than 30L may

A

Indicate dist through total body water or accumulation in certain tissues occurs for highly lipid sol drugs or those that bind extensively to tissue proteins

34
Q

What is abs of drugs

A

Process which drug enters body form its site of admin (GI tract classified as outside body)

Pharmacology (4 decks)

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