Solutions

Question 1

Definition of solution

Answer 1

Homogenous one-phase system consisting of 2 or more components

Question 2

What is the solvent in the solution?

Answer 2

Phase in which the dispersion occurs; dispersion medium/continous phase

Question 3

What is the solute in the solution?

Answer 3

Component which is dispersed as small molecules or ions in the solvent; dispersed phase

Question 4

What are the 4 types of water preparations?

Answer 4

a) Potable water
b) Purified water BP
c) Water for injection BP
d) Water free from carbon dioxide or air

Question 5

What are the 6 various methods to increase apparent solubility of compounds in an aqueous medium?

Answer 5

1. Cosolvency
2. pH control
3. Solubilisation
4. Complexation
5. Chemical modification
6. Particle size control

Question 6

What is the purpose of using cosolvents?

Answer 6

Increase solubility of a drug

Question 7

How can we improve the solubility of a weak electrolyte or non-polar compound?

Answer 7

Add water-miscible solvent in which the compound is also soluble

Question 8

What factor affects the solubility of the drug?

Answer 8

Dielectric constant

Question 9

What is the range of dielectric constant to make suitable blends?

Answer 9

25 to 80

Question 10

How do you achieve micellar solubilisation?

Answer 10

Concentration of surfactant above cmc

Question 11

What is the HLB value for hydrophilic surfactants?

Answer 11

> 15 solubilising agents

Question 12

4 factors that affect the choice of solubilising agents?

Answer 12

1. Toxicity and irritancy
2. Miscibility with solvent system
3. Compatibility with other compounds
4. Odour and taste

Question 13

How do you determine Minimum surfactant concentration?

Answer 13

1. solvent with constant concentration of the surfactant is prepared in vials
2. Different amts of drug added to vials and optical density of mixtures is determined.
3. Maximum drug conc obtained (clear solution)
4. Using same procedure, MDC values of diff surfactant conc determined
5. MDC vs surfactant conc graph
6. Minimum surfactant conc required to solubilise a certain drug conc determined from the plot

Question 14

Most complexes used for complexation are _(size) (activity)____

Answer 14

macromolecules which tend to be inactive; to ensure complex formation is easily reversible

Question 15

Hows does chemical modification of drug works?

Answer 15

Synthesis of soluble salts of the drug. The soluble salt may not have activity until it converts back to the active base in the biological system (inactive –> active)

Question 16

How to reduce particle size?

Answer 16

Milling; but less commonly used

Question 17

Why non-aq solutions might be used as a solvent for a solution?

Answer 17

• Prepare solutions of drugs which are unstable in water

- Prepare IM drug injections for depot therapy

Question 18

Name the 4 classifications of non-aq solvents

Answer 18

1. Fixed oils of vegetable origin
2. Alcohols
3. Polyhydric alcohols
4. Mineral oils
   Others

Question 19

Uses for fixed oils of vegetable origin

Answer 19

• injections, eye-drops, liniments, oral prep

- tasteless and odourless for oral prep

Question 20

Which alcohol is used for internal and external use?

Answer 20

Ethanol; low conc; as cosolvent w water in formulation of aq solns for oral and parenteral use

Question 21

Which alcohols is used for external use only?

Answer 21

• Industrial methylated spirit (ethanol w 5% methanol as a denaturant)
• Isopropanol

Question 22

Use of polyhydric alcohols?

Answer 22

• Cosolvent with water in formulation of injections

Question 23

Types of polyhydric alcohols

Answer 23

• Glycerol
• Propylene Glycol
• PEG of low MW
  All for internal and external use

Question 24

When are mineral oils used?

Answer 24

Formulation of emulsions.

Limited use as solvent as it is oily and tacky nature; vege oils generally preferred

Question 25

Example of mineral oil?

Answer 25

Liquid paraffin (internal and external use)

Question 26

What are the 'others' in the classification of non-aq solvents?

Answer 26

NOT FOR INTERNAL USE - Xylene (solvent for ear drops) - Ethyl ether (cosolvent w alcohol, extraction of crude drugs) - Isopropyl myristate, isopropyl palmitate (cosmetic pdts) - Dimethylsulphoxide, dimethylformamide, dimethylacetamide (veterinary pdts) - Kerosene (solvent for insecticides)

Question 27

What are the common additives of a pharmaceutical solution?

Answer 27

1. Buffers 2. Colours 3. Sweetening agents 4. Flavours and fragrances 5. Preservatives 6. Antioxidants 7. Isotonicity modifiers 8. Density modifiers

Question 28

Why are buffers required in a solution?

Answer 28

Resist any change in pH when acid/alkali is added to the solution seen in eye, nasal, injections e.g carbonates, citratesm gluconates

Question 29

Why are colours employed in a solution?

Answer 29

- Attractiveness; easy identification of products

Question 30

What affects the stability of the colours?

Answer 30

pH, UV radiation, presence of oxidizing/reducing agents

Question 31

What is considered natural colours?

Answer 31

variation in chemical composition and is less stable; BUT more widely accepted e.g. carotenoids, chlorophylls, anthocyanins

Question 32

What is considered synthetic colours?

Answer 32

'Coal tar' dyes Brighter colour and more stable e.g. sodium salts of sulfonic acids

Question 33

2 types of sweetening agents

Answer 33

- Natural (sucrose, fructose) | - Artificial (aspartame, saccharin)

Question 34

What is considered an artificial sweetener?

Answer 34

``` Intense sweetener (<0.2%) May have bitter or metallic after-taste ```

Question 35

Why are flavours and fragrances used in a solution?

Answer 35

Flavours for oral products - more palatable Fragrances - improve appeal of products can be natural or synthetic

Question 36

Function of isotonicity modifiers

Answer 36

Adjust tonicity of large vol solutions for parenteral and ophthalmic use

Question 37

Function of density modifiers

Answer 37

Adjust density of spinal anaesthetics

Question 38

advantages of solutions as an oral dosage form?

Answer 38

- uniform distribution of drug - easy to swallow - drug immediately available for absorption - less drug irritation than tablets/capsules

Question 39

disadvantages of solutions as an oral dosage form?

Answer 39

(1) bulky and inconvenient to transport/store (2) poorer stability, esp drugs that are prone to hydrolysis (3) prone to microbial contamination/growth (4) unpleasant taste of drug is more pronounced (2) , (3), (4) = seen in aq solution

Question 40

for what type of drugs can we use pH control to increase apparent solubility?

Answer 40

- drugs that are weak acid/ weak base: degree of ionisation affects solubility - but need to ensure pH of solution does not conflict with other product requirements

Question 41

the solubilising agents are usually what type of surfactants?

Answer 41

nonionic surfactants | - macrogol ethers etc

Question 42

for non-aq solutions, fractionated coconut oil is used as a solvent for what drug?

Answer 42

phenoxymethylpenicillin

Question 43

what are the polyhydric alcohol used for non-aq solution that are not used for humans

Answer 43

diethylene glycol, dipropylene glycol, ethylene glycol

Question 44

how are pharmaceutical solutions manufactured?

Answer 44

- propeller mixer (for less viscous) - turbine mixer (for more viscous) - paddle mixer (more viscous)

Question 45

what are some properties that can be evaluated for quality of a solution?

Answer 45

- drug content (this is regardless of ROA) - density (spinal) - tonicity (injection IV, eye drops) - viscosity (on skin) - clarity/particulate matter (IV injection, eye drop) - colour (ensure right tone/shade) - sterility (eye drops, IV injection)