Y1 Buffered & Isotonic Solutions

Question 1

Define a buffer

Answer 1

Control pH of formulated product

Question 2

Define osmosis

Answer 2

spontaneous diffusion of water from low solute concentration to high solute concentration

Double layer membrane = lipid/non-polar, semi-permeable

Osmosis leads to decrease of solute concentration

Question 3

Define colligative properties

Answer 3

Dependent on number of molecules/moles in the solution i.e. osmotic pressure is dependent

Question 4

Pharmaceutical importance?

Answer 4

As well as drug formulation, physiological differences with site of delivery must be considered/minimised - solution should be buffered and ISOTONIC

Question 5

Buffers in oral/eye solutions - uses?

Answer 5

Oral solutions or eye drops - acidic solution controlled by salt form or acids HCL, citric etc.

Question 6

Buffers in solutions for injection

Answer 6

pH range for:
IV/IM = 2-12
SC = 2.7-9.0 - dilution rate is reduced and results in irritation

pH controlled by salt form of drug, acids/bases or buffer

Question 7

What is osmolarity?

Isoosmotic?

Answer 7

Property of solution, independent on type of membrane

Number of osmoles/1L of solution

Isosmotic = same number of moles on each side, therefore no net transport from one side to the other

Question 8

Isotonic?

Answer 8

Concentration of solute is similar to environment within cells - IMPORTANT - make sure solute concentration is maintained for therapeutic effect

Depends on membrane type and the drug properties

Question 9

Hypotonic?

Answer 9

Concentration of solute is higher WITHIN the cells - water moves in to reduce concentration

Question 10

Hypertonic?

Answer 10

Concentration of solute is LOWER within the cells - water moves out to increase concentration

Question 11

Importance of buffers

Answer 11

Solubility of drug is PH DEPENDENT - buffer maintains solubility of API

Chemical stability of drug is PH AND BUFFER DEPENDENT - buffer needs to be carefully chosen

Concentration of buffer components should control pH but NOT AFFECT PHYSIOLOGICAL FUNCTIONS

Question 12

What is tonicity?

Answer 12

Measure of osmotic pressure exerted on a membrane (specific to membrane)

Solutions with same tonicity are isotonic

Relates to osmotic pressure - ONLY NON-PERMANENT MOLECULES ARE CONSIDERED

Question 13

Methods of adjusting tonicity? To achieve isotonic solution

Answer 13

1. Freezing point depression
2. Sodium chloride equivalent method (E-value)
3. Isotonic solutions or white-vincent method - USP method (V value)

Question 14

FREEZING POINT DEPRESSION

what?

Answer 14

difference between freezing point of water and freezing point of solution.

It is a colligative property