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828 Dosage > Lecture 2: Solubility > Flashcards

Lecture 2: Solubility Flashcards

1
Q

Drugs must be in a solution form for

A

-absorption
-distribution
-reaching site of action
-elimination

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2
Q

Solubility issues

A

-bodily fluids mostly aqueous
-most drugs hydrophobic
-many drugs hard to solubilize

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3
Q

Factors reducing solubility

A

= difficulty of dislodging solute molecules from crystal + difficulty of solvating dislodged molecules

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4
Q

Crystal

A

-strength makes it harder for solute molecules to dislodge
-even if mixed well, this gives difficult solubility

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5
Q

Making a solution

A

-solid –> liquid by melting
-liquid –> solution by mixing solvent

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6
Q

crystallinity

A

-solid –> liquid by “melting”
-difficulty of dislodging molecules from crystal
-(∆Hm/2.303RT)((Tm-T)/Tm)
-ideal solubility (log Xideal)

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7
Q

Hydrophobicity

A

-liquid –> solution by “mixing” solvent
-difficulty of solvating molecules
- -log y

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8
Q

Factors controlling solubility

A

log Xobs = -(∆Hm/2.303RT)((Tm-T)/Tm) -log y

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9
Q

Graph of Solubility Equation

A

SLIDE 9
-Log Xobs = horizontal baseline
-Log Xideal= black box above baseline
- -log y = white box on top of black box to 0

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10
Q

Breakdown of solubility contributions

A

Slide 10

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11
Q

“like dissolves like”

A

-would be true if everything was liquid INSTEAD:
-higher melting point of solid = lower solubility

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12
Q

Higher melting point

A

lower solubilty

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13
Q

Dissolution

A

-end goal for drug
-solubility affects rate

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14
Q

Noyes-Whitney Equation

A

(dC/dt) = DA/h (Cs-C)

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15
Q

Tablet to tissue

A

tablet to GI tract to intestinal wall to systemic circulation to target tissue

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16
Q

GI tract

A

-solubility/dissolution
-stability
sends to intestinal wall

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17
Q

Intestinal wall

A

-permeability
-stability
sends to circulation

18
Q

Systemic Circulation

A

-first-pass
-metabolism/clearance
sends to target tissue

19
Q

Drug factors that affect dissolution rate

A

-solubility (change in Cs)
-particle size (change in A)
-pH
-types of solid (salts, hydrates, polymorphs, amorphous)

20
Q

Dosage form factors that affect dissolution rate

A

-all the listed drug factors
-disintegration rate
-excipients
-variation in manufacturing conditions

21
Q

increase solubilizing excipient use (increase Cs)

increase solubility

A

increase dissolution

22
Q

Increase surface area (A)

A

increase dissolution

23
Q

Combined effect of solubilizing excipient and particle size reduction on bioavailability

A

dissolves more quicker

24
Q

Effect of pH on solubility and dissoulution

A

low until big spike up at pH 8 (or maybe close to pka??) and as pH increases from 8 dissoultion stops and solubility levels off

25
Q

Salt formation

A

-over 50% of drugs
-easiest way to increase solubility

26
Q

salt formation from acidic drug

A

-made by crystallizing it from a solution where pH>pKa of drug

27
Q

salt formation from basic drug

A

-made by crystallizing drug in solution where pH<pKa of drug

28
Q

Spring and parachute effect

A

dissolution of salt spikes until converted to free acid then falls until leveled out to solubility of free acid SLIDE 29

29
Q

Complexation

A

drug molecule forming complex with cyclodextrin molecule

30
Q

Complexation equation

A

Kc = [D-CD] / [D][CD]
-equilibrium

31
Q

Cosolvents

A

-affects solubility in a log-linear relationship
-can only change -log y part of solubility equation
-moves the entire box up??

32
Q

“brick dust” limitation

A

must disrupt the orderly crystal structure

33
Q

amorphous form

A

-more soluble and faster dissolution
-generated by getting drug into liquid form and solidifying quickly so there is no time for crystallization

34
Q

Drugs need to be ____ in the aqueous bodily fluids in order to work

A

solubilized

35
Q

drugs with ___ aqueous solubility are more the rule than the exception

A

low

36
Q

Drug solubility dependent on:

A
  1. crystallinity (brick dust)
  2. hydrophobicity (wax)
37
Q

___ impacts ____ rate but is not the only factor to do so

A

solubility, dissolution

38
Q

____ is the simplest way of changing dissolution without changing solubility

A

Particle size

39
Q

Solubility can be changes by:

A

-pH in liquid prep
-pH through salt formation in solids
-complexation
-cosolvents

40
Q

For really stubborn “brick dust” drugs or when
hitting the brick wall with cosolvents, disrupting the
___________ becomes
necessary

A

crystal (amorphous formulations)

828 Dosage (27 decks)

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