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week 10 (Y1) > the medicine > Flashcards

the medicine Flashcards

1
Q

what are sink conditions?

A

1) where the solute may be removed from solution at a faster rate than it is produced

2) the volume of the solution maybe so large that C does not exceed 10% of Cs

in this case (Cs-C)≈Cs

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2
Q

What are non-sink conditions

A

where C exceeds 10% of Cs

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3
Q

When does the overall dissolution rate equal zero

A

when C=Cs

The solution is saturated with solute

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4
Q

what is the significance of Noyes-Whitney

A

The Noyes-Whitney function is used to represent how the solid material is dissolved into solution

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5
Q

what is dissolution?

A

Dissolution is the process where a solute in gaseous, liquid, or solid phase dissolves in a solvent to form a solution.

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6
Q

what is the Noyes-whitney equation

A

dm/dt = D.A.dC/dx

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7
Q

what is dm

A

change in mass [mg]

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8
Q

what is dt

A

Change in time [seconds.]

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9
Q

what is D

A

The diffusion coefficient (cm^2/s)

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10
Q

what is A

A

surface area (cm^2)

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11
Q

what is dC

A

change in concentration (mg/cm^3)

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12
Q

what is dx

A

change in distance (cm)

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13
Q

what does dC/dx describe

A

The concentration gradient

where: dC/dx = Cs-C/h

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14
Q

what is the notes-whitney equation for a single Spherical particle

A

dm/dt = D.A.(Cs-C)/h

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15
Q

What is viscosity?

A

The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of “thickness”: for example, syrup has a higher viscosity than water.

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16
Q

What happens to the rights of dissolution when the diffusion coefficient is decreased?

A

The rate is also decreased [this can happen when viscosity is increased.]

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17
Q

what happens to the rate of dissolution if the particle size is increased? (A)

A

The rate decreases

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18
Q

what is Cs

A

the saturation solubility of the drug in solution in the diffusion layer

19
Q

what is C

A

Drug concentration in bulk solution
at time t (g/mL)

20
Q

What is a solution?

A

A special type of homogenous mixture, composed of two or more substances

21
Q

What are some advantages of a solution in pharmacy?

A

easier to swallow than solids
Absorption is rapid
The onset of action is faster than solid dosage forms
Homogenous dosage
Attractive mouth feel and appearance

22
Q

What are some disadvantages of a solution in pharmacy?

A

they are bulky to transport
The dosage is dependent on the patient’s ability
Possible microbial contamination
May require taste mashing
Less stable than solid dosage forms

23
Q

what are some examples of a solvent [aqueous solutions]

A

water, is the most widely used solvent/cosolvent

24
Q

What are some examples of a solvent [nonaqueous solution]

A

oils, alcohols, glycols

25
Q

what is dissolution? [uni definition.]

A

It is a process/transfer of molecules and ions from a solid state to a solution

26
Q

What is solubility?

A

A Physio chemical property of molecules [drugs]

It depends on the balance of lipophilic and hydrophilic groups

And how much of a drug is dissolving in a specific volume?

27
Q

What does having a higher intrinsic solubility mean?

A

there are more hydroxyl groups, more hydrophilic groups. Which increase the affinity between the molecule and the solvent.

More of the molecule in the solvent is packed in before reaching saturation

28
Q

what is the effect of pH on the solubility of acids? Increasing the pH:

A

This will increase solubility due to increased interaction of the ionized form with water. The acids will donate to the protons, and become more charged.

29
Q

what is the effect of pH on the solubility of bases?
Decreasing the pH of a solution containing bases

A

decreasing the pH of solutions, containing bases will cause ionization This will increase solubility, due to an increased interaction of the ionized form

30
Q

What is a partitioning coefficient?

A

They describe the distribution of solvents between a mixture of immiscible liquids

31
Q

What is an immiscible liquid?

A

where to liquids stay as two different layers

32
Q

What is the partition coefficient equation?

A

P=Co/Cw

[] of the top / [] of the bottom liquid

33
Q

How do we know if the molecule is more hydrophilic or lipophilic by using the partition coefficient?

A

we logP

logP>0 = the molecule is more lipophilic
logP<0 = the molecule is more hydrophilic. [polar].

34
Q

Gastrointestinal absorption the two main classes

A

there are two main classes of transport through the gastrointestinal tract/membrane

1) passive
2) carrier mediated

Passive transport [diffusion] is driven by a concentration gradient

35
Q

Why is the gut membrane more permeable to un ionized forms of drugs?

A

due to a greater liquid solubility, and they are usually smaller molecules. That is also no charge effects

There is rapid absorption when the drugs is un ionized

36
Q

when are acids usually absorbed

A

from a low pH

For example, the stomach

37
Q

when are bases usually absorbed

A

from a higher pH/environment

For example, the intestine

38
Q

Why is absorption from the stomach not extensive?

A

because of the muscle lining, small surface area, short residence time

39
Q

Why is the small intestine a more favorable environments for absorption?

A

because of a large surface area, thin barrier, long residence time

40
Q

what is residence time

A

the duration of persistence of a mass or substance in a medium or place

The amount of time, a molecule or substance has stayed in somewhere (the longer it has stayed the more likely it is favorable for absorption)

41
Q

what is the %ionized calculation

A

%ionised = (I/I+U) X 100

I=amount of ionised drug
U= amount of unionized drug

42
Q

what is the % ionised equation for acids

A

% ionised = 100/1+10^pKa-pH

43
Q

what is the % ionised equation for bases

A

% ionised = 100/1+10^pH-pKa

week 10 (Y1) (3 decks)

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