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Pharmacology > Principles Of Drug Therapy 2 > Flashcards

Principles Of Drug Therapy 2 Flashcards

1
Q

Abs w/ drug IV?

A

Absorption is bypassed

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2
Q

How can a drug be abs and enter cells?

A

Since they’re not natural metabolites and have no carriers, must be soluble in water and fat (have fave partition coefficient)

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3
Q

What’s partition coefficient?

A

[drug]oil/[drug]water

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4
Q

Classes of most drugs?

A

Neutral and uncharged
Weak acids and bases
Salts of strong acids and bases

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5
Q

What does the PC depend on?

A

C# and OH

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6
Q

Weak acids and bases?

A

Can donate or accept H reversibly

Weak = both ionized and unionized forms of drug are present in equilibrium in aq solution

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7
Q

Ka?

A

= base x H/ acid

B/A depends on pH and pK

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8
Q

Salicylic acid? Diphenhydramine?

A

Typical weak acid drug

At pH 7, B:A = 10,000:1

Weak base
1:100

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9
Q

Strong A and Bs?

A

Anions of acids

Cations of bases

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10
Q

How do drugs w/ mult weak acids and bases act?

A

Like strong ones cuz the conc of uncharged species is negligible

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11
Q

Ipratroprium?

A

Quarternary ammonium
Has + charge, no H to be removed
Atropine at pH 7, b:a, 1:500

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12
Q

How are drugs transported?

A

Bilayer diffusion
Pores
Active or passive trans

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13
Q

How to diffuse?

A

Fave PC, uncharged

So that there’s: Abs from GI, enter cells (intracell receptor), entering CNS (receptor in BBB)

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14
Q

Passive diffusion?

A

Driven by conc gradient across membrane

Spontaneous downhill, dissipates the gradient

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15
Q

Salicylic acid and Diphenhydramine in transporting a weak base?

A

They exist as 2 forms;

Acid: charged
Base: uncharged

Rate of trans depends on conc of base

W/ trans of weak acid, “” of acid

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16
Q

What happens if ph isn’t same on each side of membrane?

A

Cation accumulates on side with lower pH

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17
Q

What is ion trapping?

A

Diff in conc of weak A and Bs between blood and diff compartments cuz of pH diff

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18
Q

What allows pore transport?

Where are pores?

A

Hydrostatic pressure gradient

Pores are in capillaries and glom

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19
Q

Pores essential for?

A

Trans of quart amm drugs (succinylcholine)
-water soluble, charged

ONLY SIZE restricts

Most important way for most drugs to get into tissues

NOT IN BBB!

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20
Q

How is heparin transported?

A

It’s too big, so limited to the plasma

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21
Q

What limits rate of entry of drug into most tissues?

A

Blood flow!

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22
Q

Pores and liver sinusoids?

A

Large regulated pores: fenestrae
No basement membrane
No barrier to proteins like albumin

23
Q

Features of drug active transport?

A

Couples trans to chem rxn or to trans of another species using cell E to drive transport

Can generate a gradient

Transported species:
-charged bases, anions of acids, fixed charge
-permanently charged quart drugs
Drugs with same charge can compete

24
Q

Transport proteins are used to?

A

Couple the input of E to drug mvmt

Only in cells that have the required transport proteins

25
Q

Key mechanisms of active trans?

A

NaKATPase in mem

  • Na in, K out gradients across mem
  • along w/ K channels: positive outside electrical mem potential

These gradients drive drug transport

26
Q

What’s the role of transporters if drugs only need good PC to enter?

A

To protect against xenobiotics

Transporters in liver, kidney and intestine epithelia: roles in abs and elim

Some in other tissues (brain, placenta, testis) can also limit distribution

27
Q

Features of most drug and xeno transporters?

Locations?

A

From SLC (315 in 48 fam) and ABC (49 in 7) families

Broad substrate selectivity, trans of many xeno
*drug interactions

PT of nephron (excretion)
Hepatocytes, GI
-into cells: biotransformation
-out of cells: bile or blood
Vasc endo in brain, Choroid plexus (barrier between blood and CSF), etc
-protects tissue by pumping drugs out, limiting distribution and minimizing harm
-problem when drug needs to get into brain

28
Q

Rate of abs depends on? Major sites?

A

Thickness of barrier
How well site is perfused
Area of surface exposed to drug

GI, lungs, skin, injection sites

29
Q

How drugs are abs from GI?

A

Passive non ionic diffusion through epi cell mem
Neutral drugs: abs rate dependent on PC
Weak A+B: “” PC, pH, pK in GI
Fixed charge drugs: poorly absorbed

30
Q

What can be abs from stomach?

A

Weak acids

Weak bases CANT b/c conc on uncharged base is low

31
Q

Abs from SI?

A

Almost all drugs taken orally cuz of its large surface area

32
Q

How are drugs abs from GI moved?

A

To liver via hepatic portal vein b4 entering systemic circulation; GI transporters

33
Q

First pass effect?

A

Metabolism of oral drug by liver and GI before reaching systemic circ

Nitroglycerin, morphine, etc
Drugs with high first pass met are given another route

34
Q

What’s bioavailability?

A

When the unmet drug goes into sys circ = (100-x-y-z)%

35
Q

Why might oral bioavailability be <100%?

A

Abs less than 100%, low PC or P-gp transport

Metabolism in GI or liver b4

36
Q

Drug with 0% bioavailability?

A

Useful if the metabolite is the active agent

37
Q

Other routes to avoid liver?

A

Sublingual (all of drug to sys), rectal (50% of drug to sys b4 liver, incomplete abs)

38
Q

Major routes of parenteral admin?

A

IV, IM, SC, topical

39
Q

Pros and cons of IV?

A

Pros:
Fast, no abs!
Control over blood conc

Cons:
Blood conc can rise quickly
Adv effects
Drug must be in aq solution 
Can't be reversed!!
40
Q

Pros and cons of IM?

A

Abs via cap pores or lymph for larger, depends on blood flow and fat content

Pros:
Varied abs rate (fast from aq)
Slow but sustained abs of poorly water soluble drugs

Cons:
Painful
Avoid w/ anticoagulants

41
Q

Pros and cons of SC?

A

Abs via cap pores or lymph for larger, depends on blood flow and fat content

Pros:
Varied abs rate (fast from aq)
Slower for insoluble – sustained effect
Solid pellets insertion for long term release

Cons:
Can’t be used with drugs that irritate the tissue

42
Q

Features of tropical and transdermal drugs?

A

Local effect, minimize sys exposure
Patches: Slow continuous sys supply of drug

Need to be potent and have fave PC to be abs thru skin
Inflamm skin increases abs
Site of admin is important: ventral forearm has 1% abs

43
Q

What does distribution rate depend on?

A

Perm of cap
Blood flow to tissues

Drugs reach peak conc in organs with most blood, quickly

44
Q

What’s volume of distribution?

A

The apparent volume of a drug after it’s been abs and distributed

=(f)(Xadm)/[X]blood
Vol/kg
May not correspond to a real volume if drug conc is diff in each tissue

45
Q

Whats Vd?

A

Relationship between the amount of drug in the body and the plasma drug conc

Dose x f = desired [X]blood x Vd

46
Q

What determines a drug’s Vd?

A

Ability to leave blood
-drug properties
-plasma protein binding keeps more in blood
-if all drug is in blood, Vd = blood vol
Ability to enter cells
Extra vascular drug reservoirs and storage
-protein binding in xtravasc tissues
-if drug leaves blood, Vd rises above blood vol
-if 0% drug in blood, Vd to infinity

47
Q

Plasma protein binding features?

A

Acidic drugs bind to albumin in blood, basic to alpha 1 acid glycoprotein

As free drug disappears, more drug dissc from protein

protein binding buffers free drug conc

48
Q

Drug distribution to the BBB?

A
  • Tight junctions in brain
  • Capillaries surrounded by glial cells, not ECF
  • endothelial cells have transporters (p-glycoprotein) that actively pump drug out)

Drugs enter CNS thru passive non ionic diff across 4 bilayers, need good PC

Chemoreceptor trigger zone and hypothalamus lack the barrier

49
Q

Placental distribution?

A

No pores
Fail to cross: large, mult charged with low lipid solubility
Lipophilic with good PC enter by simple passive diff
P-glycoprotein to export drugs
Fetal blood more acidic at 7.2

50
Q

Distribution to other organs?

A 
Testes and prostrate:
Sertoli cells: 
-tight junctions
-transporters
-No pores

Joints/synovial fluid:
-no pores unless joint is inflamed

Lungs:
-large cap surf area

51
Q

How do drugs get into secreted fluids?

A

Passive non ionic diffusion

52
Q

What’s ion trapping?

A

When pH of secreted fluids differs from that of plasma

53
Q

What factors affect plasma protein binding?

A

Drug interaction, disease, age

54
Q

Drug storage?

A

Plasma protein binding
Tissue accumulation w/ slow release (drugs w/ aff for Ca or phosphate acc in bone or teeth: tetracycline antibiotics and heavy metals)

Pharmacology (7 decks)

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