Solutions

Question 1

what is a solution

Answer 1

a homogenous one-phase system consisting of two or more components

Question 2

solvent

Answer 2

phase in which the dispersion occurs

Question 3

solute

Answer 3

the component which is dispersed as small molecules or ions in the solvent

Question 4

types of solution

Answer 4

aqueous or non-aqueous

Question 5

advantage of solutions as oral dosage form

Answer 5

1. easy to swallow (peds)
2. drug immediately available for absorption
3. uniform distribution
4. less irritation than capsules

Question 6

disadvantage of solutions as oral dosage form

Answer 6

1. bulky and inconvenient to transport or store
2. poor stability (esp if drug susceptible to hydrolysis)
3. prone to microbial growth/ contamination
4. unpleasant taste of drug

Question 7

types of preparations to be made

Answer 7

1. potable water
2. purified water BP
3. water for injection BP
4. water free from carbon dioxide or air

Question 8

cosolvency

Answer 8

solubility of a weak electrolyte or non-polar compound in water can be improved by the addition of a water-miscible solvent in which the compound is also soluble

Question 9

what are cosolvents

Answer 9

vehicles used in combination to increase the solubility of a drug

Question 10

what is the solubility of a drug affected by

Answer 10

dielectric constant of solvent system, ideally dielectric constant should be 25-80

Question 11

pH control

Answer 11

if drug is either a weak acid/base, its degree of ionisation and consequently its solubility are influenced by the pH of the solubility, ensure pH does not conflict with other product requirement

Question 12

solubilization

Answer 12

concentration of surfactant used should be above its critical micellar concentration- micellar solubilization

Question 13

what is the range of values for hydrophilic surfactant to be a useful solubilising agent

Answer 13

above 15 HLB value

Question 14

how can solubility be improved

Answer 14

adding surfactant, however a large excess of surfactant is undesirable

Question 15

factors that affect choice of solubilising agents

Answer 15

1. toxicity and irritancy
2. miscibility with solvent system
3. compatibility with other components
4. odour and taste

Question 16

example of solutions with solubilising agents

Answer 16

1. fat soluble vitamins + polysorbates
2. iodine + macrogol ethers
3. steroids + polyoxyethylated castor oil
4. cresol + chloroxylenol + potassium soap of fatty acids

Question 17

example of combi of cosolvent and solubilising agents employed to improve solubility

Answer 17

1. vitamin A + polysorbate 80 + glycerol

2. chloroxylenol + potassium ricinoleate + ethanol terpineol

Question 18

chemical modification

Answer 18

involves synthesis of soluble salts of the drug; soluble salt which may not have any activity is converted back to active base in biological system

Question 19

example of chemical modification

Answer 19

1. sodium phosphate salts of hydrocortisone, prednisolone, and betamethasone
2. sodium succinate salt of chloramphenicol

Question 20

particle size reduction

Answer 20

size and shape of very small particles (< 1 micron) can affect their solubility, but less commonly employed to improve solubility

Question 21

how are particle size commonly reduced

Answer 21

milling

Question 22

non-aqueous solutions

Answer 22

solvents are classified as

1. fixed oils of vegetable origin,
2. alcohols,
3. polyhydric alcohols,
4. mineral oils
5. and others

Question 23

why are non-aq solution employed

Answer 23

1. prepare solution of drugs which are unstable in water

2. prepare intramuscular injections of drugs for depot therapy

Question 24

alcohol for external use only

Answer 24

1. industrial methylated spirit (ethanol with 5% methanol as denaturant)
2. isopropanol

Question 25

alcohol

Answer 25

commonly employed in low concentration, as a cosolvent with water in the formulation of aqueous solution for oral and parenteral use

Question 26

polyhydric alcohols

Answer 26

commonly used as cosolvent with water in the formulation of injections

Question 27

example of polyhydric alcohol

Answer 27

1. glycercol (E & I): phenol ear drops BPC 1973 2. propylene glycol (E & I): Digoxin injection BP, Phenobarbitone Injection BP, Chloramphenicol Ear Drops BP 3. Polyethylene glycols of low MR (E&I): Erythromycin Ethylsuccinate injection BP 4. Dipropylene Glycol, Diethylene glycol, Ethylene glycol (E only cause toxic): veterinary and horticultural use

Question 28

Mineral oils

Answer 28

internal external use, limited use as solvent in pharma preparation due to oily tacky nature; veg oil preferred; more often used in formulation of emulsion

Question 29

what are not for internal use

Answer 29

1. xylene (eardrops) 2. ethyl ether (cosolvent with OH in collodions, extraction of crude drug) 3. isopropyl myristate, isopropyl palmitate (cosmetics) 4. dimethylsulphoxide, dimethylformamide, dimethylacetamide (veterinary) 5. kerosene (insecticides)

Question 30

buffers

Answer 30

employed to resist any change in pH when acid/alkali added

Question 31

example of buffers

Answer 31

carbonates, citrates, gluconates, lactates, phosphates, tartrates, borates

Question 32

color

Answer 32

employ to improve attractiveness and enable easy identification of products

Question 33

how may stability of color be affected by

Answer 33

pH, ultraviolet radiation, presence of oxidizing or reducin agents

Question 34

types of colors

Answer 34

1. natural: show variation in chemical composition and are less stable, but more widely accepted (carotenoids, chlorophylls, anthocyanins) 2. synthetic: coal tar dyes, brighter n=more stable colors (sodium salts of sulphonic acids)

Question 35

natural sweetening agent

Answer 35

sucrose, fructose, sorbitol, mannitol, glycerol, xylitol, hydrogenated glucose syrup, isomalt, honey , liquorice

Question 36

artificial sweetening agent

Answer 36

``` intensify sweeteners (<0.2%); tendency to impart bitter/ metallic after taste eg: saccharin, aspartame, acesulfame, potassium, thaumatin ```

Question 37

flavours

Answer 37

employed to make oral products more palatable while fragrances improve the appeal of the product

Question 38

eg of flavor/fragrance

Answer 38

fruit juice, aromatic oils, herbs, spices

Question 39

preservative

Answer 39

prevent microbial contamination of product

Question 40

antioxidants

Answer 40

prevents degradation of compounds by oxidation

Question 41

isotonicity modifiers

Answer 41

adjust tonicity of large volume solutions for parenteral and ophthalmic use

Question 42

density modifiers

Answer 42

to adjust the density of spinal anaesthetics

Question 43

how are pharmaceutical solutions manufactured

Answer 43

mixers: propeller, turbine, paddle

Question 44

how are pharmaceutical solutions evaluated for quality

Answer 44

drug content, density, tonixity, viscoxity (topical), clarity/particulate, color, sterility (parental/opth)