Exam 2 Parenteral Products 5

Question 1

Are the term isotonic and iso-osmotic the same?

Answer 1

no → sometimes the same but not always

Question 2

What is the definition of isotonicity?

Answer 2

maintaining and possessing a uniform tension or tone between a living cell (membrane of cell) and the environment

Question 3

How do concentrations tend to equalize over time?

Answer 3

two solutions of different concentration are separated by a membrane → eventually with some time there will be equal concentration on each side because there is movement from higher to lower concentration of the solute/water until each side has equal concentration

Question 4

What are the two ways in which concentrations tend to equalize over time?

Answer 4

1. diffusion

2. osmosis

Question 5

No matter if its a solute or water, in what direction does it move in?

Answer 5

from high to low concentration!

Question 6

What is diffusion?

Answer 6

solute moves from high to low concentration of solute until both sides of the permeable membrane are equal → has a permeable membrane which allows anything to go through

Question 7

What is osmosis?

Answer 7

water moves from high to low concentration of water → water goes in through the semipermeable membrane and dilutes it until there is equal solute concentration on both sides (but the side that the water goes in will expand like a balloon)

Question 8

With a semipermeable membrane, what things can pass through?

Answer 8

let’s some things in/out → keeps solute in place but water is allowed to go through

Question 9

What is the difference between a permeable and a semipermeable membrane?

Answer 9

permeable → let’s anything go through (including solute)

semipermeable → let’s some things go through like water (but not solute)

Question 10

How do parenteral vehicles affect isotonicity?

Answer 10

parenteral vehicles have the ability to shrink or burst open blood and venous endothelial cells

Question 11

All living cells (aka their cell membranes) have what kind of membrane?

Answer 11

semipermeable membrane

Question 12

What are the different types of permeability and how does that affect the cell?

Answer 12

1. impermeable (nothing goes through) → cell starves
2. permeable (everything goes through) → cell ends as an empty shell and is dead again (like a tea bag)
3. semipermeable (some things can cross while other things can’t) → viable cell

Question 13

With a semipermeable membrane, what can always go through?

Answer 13

water!

Question 14

What happens if SWFI solution is added to some RBCs that are just floating around?

Answer 14

water flows into the RBCs and then bursts open (aka hemolysis) since RBCs are not elastic and can break/burst very easily

Question 15

What are some things to note if RBCs are in the presence of SWFI?

Answer 15

1. different concentrations inside and outside the cell membrane
2. tendency to equalize concentrations remains → what can move will move!
3. a catch → the membrane is semipermeable (living cell)
4. only water can go through (not the solute)
5. water will move to dilute the more concentrated side → cell will start to sell since the cell has a high solute concentration (aka low water concentration) → cell will burst
6. does not have to be water, any hypotonic vehicle will do the same!

Question 16

What are the main differences between isotonicity and osmolarity?

Answer 16

isotonicity refers to if it preserves the life of the cell or not while osmolarity refers to a number

Question 17

How can we measure the risk of any given preparation?

Answer 17

1. by knowing the osmolarity (is a number, a concentration) or the osmolality of the preparation
2. we use an instrument called an osmometer to measure this property
3. this is a practical use of colligative properties

Question 18

What are examples of colligative properties?

Answer 18

1. freezing point depression → like putting salt on roads
2. lowering of vapor pressure → used in humidifiers and tobacco
3. osmotic pressure → pressure inside/outside of living cell
4. elevation of boiling point → things are harder to boil compared to water

Question 19

What are some important things to know about colligative properties?

Answer 19

1. properties of solutions that depend on the quantity of “molecular particles” (either molecules, ions, or m-particles) in solution rather than the chemical nature of the dissolved materials
2. any solute (drug, electrolyte, sugar) dissolved has the same effect as something else
3. osmolarity and osmolality are determined by the total (added up) concentration of solutes dissolved (counted as m-particles) including the drug

Question 20

What are the 4 different ways to measure osmolarity/osmolality?

Answer 20

1. freezing point depression → puts little amount of solution in a conical vial and the machine tells the osmolarity concentration with the temperature it takes for it to freeze at
2. lowering of vapor pressure → machine will measure vapor concentration to give the osmolarity concentration
3. osmotic pressure → will make one side grow
4. assay → can measure it chemically

Question 21

What are the two main methods to measure osmolarity/osmolality?

Answer 21

1. freezing point depression
2. lowering of vapor pressure

will get results in a minute

Question 22

What is an example of molarity v osmolarity?

Answer 22

NaCl (solid) → Na+ + Cl- (solution)

1 Molecule → 2 ions
1 molecule → 2 m-particles
1 mol → 2 Osmols
1 mole/L → 2 Osmol/L

Question 23

What is another example of molarity v osmolarity?

Answer 23

dextrose (solid) → dextrose (solution)

1 Molecule → 1 Molecule
1 molecule → 1 m-particle
1 mol → 1 Osmol
1 mol/L → 1 Osmol/L

Question 24

What does osmolarity take into account?

Answer 24

it takes into account if the molecule dissociates or not → if it does dissociate into ions then molarity ≠ osmolarity but if it doesn’t dissociate then molarity = osmolarity

Question 25

What is the equation for molarity?

Answer 25

moles of solute / liter of solution

Question 26

What is the equation for osmolarity?

Answer 26

Osmoles of solute / liter of solution = # moles of solute / liter of solution * # m-particles / 1 molecule

Question 27

How can molarity and osmolarity be different?

Answer 27

1. salt molecules dissociate and increase the number of m-particles in solution
2. NaCl dissociates which gives 2 m-particles per molecule
3. so do salts of drugs like sodium, potassium, hydrochloride, and acetate salts → electrolytes will also give more than one m-particle per molecule

Question 28

What is the equation of molarity?

Answer 28

molarity = amount of solute / “amount” (volume) of solute + volume of solvent

Question 29

What is the equation for molality?

Answer 29

molality = amount of solute / amount of (only) solvent

Question 30

What is the difference between molarity and molality?

Answer 30

molarity takes into consideration the volume of solvent and solute while molality is only the volume of solvent → molality is more of a ratio

Question 31

What is the equation for osmolarity?

Answer 31

osmolarity = # of osmoles of solute / volume of solvent + solute

Question 32

What is the equation for osmolality?

Answer 32

osmolality = # osmoles of solute / wt (in kg) of solvent

Question 33

In terms of variables, what is the equation for osmolarity and osmolality?

Answer 33

osmolarity = a/a+b
osmolality = a/b

Question 34

When are osmolarity and osmolality numerically similar?

Answer 34

if a is tiny (aka a low concentration)

Question 35

When are osmolarity and osmolality not numerically similar?

Answer 35

when a is not tiny (aka high concentration)

Question 36

What is the advantage of 70% dextrose (basically like syrup)?

Answer 36

can give sizable increase in molarity without increasing volume too much which is good for patients that can’t get too much volume (unlike D5W that needs larger volume)

Question 37

What are some things to note about osmolarity and osmolality?

Answer 37

1. often used interchangeably
2. we can get away with treating them as equivalent at low concentrations
3. very dangerous to treat them as equivalent at high concentrations (TPN dextrose solutions come at high concentrations → the exception)

Question 38

What is the value of serum osmolarity?

Answer 38

280-300 mOsmol/L → we want to use 300 mOsmol/L for our calculations

Question 39

How is iso-osmotic and isotonic different?

Answer 39

1. osmolarity is a number, a concentration value, measured by an instrument (osmometer) → can be measured or calculated
2. the instrument will not distinguish between NaCl and sulfuric acid but a living cell will → the instrument can’t know if the cell would die or not
3. tonicity refers to the effect on living cells
4. if a solution of sulfuric acid gives the same osmolarity value as NS, the two solutions are iso-osmotic (same number from the machine) but only NS is isotonic (compatible with living cells)

Question 40

Normal saline (NS) is both what?

Answer 40

both iso-osmotic and isotonic

Question 41

What is the basis of the difference between iso-osmotic and isotonic?

Answer 41

can have something that is iso-osmotic that can still kill the cell (aka not isotonic) → the two terms are not the same

Question 42

Are the terms iso-osmotic and isotonic equivalent/interchangeable?

Answer 42

no → the two concepts are completely different in which osmolarity is a number that is measured by an instrument while isotonic refers to its effect on living cells (aka will it kill the cell or not)

Question 43

What are important things to note about iso-osmotic and isotonic?

Answer 43

1. if a solution is isotonic, it is also iso-osmotic → not always the other way around in which if it is iso-osmotic, it might not be isotonic
2. if you mix iso-osmotic solutions, you get an iso-osmotic mixed solution
3. if you mix isotonic solutions, you get an isotonic mixed solution (all non-damaging solutes) → if the solute is not dangerous and at the right concentration
4. normal saline (NS) and D5W are both isotonic but ARE NOT interchangeable in every case → have to check the drug monograph
5. compatibility with the product is a separate issue that must be checked every time

Question 44

Even though for many products, NS and D5W are equally suitable diluents, but why is this not the case every time?

Answer 44

1. normal saline and D5W ARE NOT always interchangeable
2. replacing one for the other can be disastrous in some cases
3. make it a conscious point to ALWAYS check the monograph or package insert → if can’t find it, then use whichever diluent is available
4. do not fall in the trap of “getting used” to seeing NS and D5W as equally suitable diluents for your CSP

Question 45

What happens if an iso-osmotic solution is used to dissolve a large amount of drug?

Answer 45

the result will be a hypertonic (higher concentration) solution (the presence of the drug adds to the total osmolarity)

Question 46

What is an example of an iso-osmotic solution that is used to dissolve a large amount of drug to create a hyperosmotic solution?

Answer 46

if iso-osmotic with plasma → 300 mOsmol/L but the presence of the drug also adds to it so it will be greater than 300 mOsmol/L (aka hyperosmotic)

Question 47

How are hyperosmotic solutions the lesser of two evils?

Answer 47

1. a hypo-osmotic solution can burst cells open (hemolysis → a big no no)
2. a hyperosmotic solution will shrink cells (like raisins which is okay)
3. iso-osmolarity is always desirable, but a slightly hyperosmotic solution is not as bad
4. in general, hypo-osmotic solutions are WORSE than hyperosmotic ones