Medicinal Solutions

Question 1

1.
Define the following terminologies:
1.Pharmaceutical solutions.
2.Syrups
3.Elixirs
4.Spirits
5.Tinctures

Answer 1

1.Solutions – complete distribution of solute in solvent, homogeneous at molecular level (transparent).
2.Syrups - aqueous solutions containing a sugar or sugar substitute with or without added flavourings or drugs.
3.Elixirs – sweetened hydroalcoholic (combinations of water and ethanol) solutions.
4.Spirits – hydroalcoholic solutions of aromatic materials.
5.Tinctures – alcoholic or hydroalcoholic solutions of chemical or soluble constituents of vegetable drugs. A tincture is typically an extract of plant or animal material dissolved in ethanol

Question 2

Give three examples of hydrophilic polymers commonly used for viscosity enhancement of solutions, stating the general classification, source and rheological properties.

Answer 2

1.Synthetic
- poly(acrylic acid); poly(vinyl pyrrolidine); poly(ethylene glycol) or poly(ethylene oxide).

2.Semi-synthetic
- cellulose ethers (MC, HPMC, HEC, EC, CMC)

3.Natural
- polysaccharides such as acacia (arabic), tragacanth, alginates, starch, xanthan, hyaluron, carrageenan
(contains S), cellulose, guar, maltodextrin, polydextrose, chitin/chitosan (contains N).

4.Newtonian
- dilute solutions (most), PVP, water, alcohol

5. Non-Newtonian
   most give pseudoplastic solutions at low to moderate - concentration (notable – PAA, cellulose ethers,
   vegetable gums, xanthan.
   Many salt solutions, ketchup, mayonnaise, gravy, toothpaste, custard, shampoo

Question 3

What is a solution?

Answer 3

A mixture of two or more components that form a single phase that is homogenous down to the molecular level.

A solid dissolved in a solvent

This can be,
Solute (dispersed phase) dissolved in a solvent (dispersion medium)
The solute can be solid, liquid and gas.

Question 4

What is a suspension?

Answer 4

A solid dispersed in a liquid

Question 5

What is an emulsion?

Answer 5

A liquid dispersed in a liquid

Question 6

What is miscibility?

Answer 6

Miscibility is the property of two substances to mix in all proportions forming a homogeneous mixture (a solution). When a liquid is dissolved/dispersed in a liquid or a gas is dissolve/dispersed in a gas.

Question 7

What does the sugar do in a syrup?

Answer 7

Syrups are 80% sugar, therefore they act as preservative - bacteria are burst open by osmotic pressure on the cell wall

Question 8

What are some advantages of solutions?

Answer 8

Drug is uniformly distributed throughout solution.
Uniform dose providing volume is measured accurately
Absorption is not delayed as drug is already in solution
Easy to swallow (oral solutions)

Question 9

What are the disadvantages of solutions?

Answer 9

Generally less stable than solid dosage forms
Unpleasant flavours can be difficult to mask
Bulky to carry around
A 5 mL “spoon” or syringe is required to measure the dose (oral)

Question 10

Examples of aqueous solutions?

Answer 10

Syrup BP
Sucrose 66.7% w/v
Water to 100%
High concentration necessary for stability
High osmotic pressure unlikely to support microbial growth
Microbial growth more likely if diluted below 66.7%w/v

Nasal spray - mainly isotonic saline (0.9%w/v)
- most frequent used for treatment of common cold or to administer local steroids for the treatment of allergic rhinitis e.g ephedrine, xylometazoline, beclometasone.

Question 11

Give examples of pharmaceutical solutions?

Answer 11

Eye drops - at their simplest, isotonic saline
- antibiotics ( chloramphenicol, neomycin)
Ear Drops - antibiotics (as for eye)
- steroids ( as for nose)
- chlorbutanol / arachis oil (oily solution)
- Oropharynx - saline, steroids, antiseptic mouthwashes (mouth/ throat)
- Enemas - oily or aqueous solutions administered rectally

Question 12

Newtonian examples

Answer 12

Castor oil, olive oil, glycerol, water,
ethanol, chloroform etc

Question 13

Plastic examples

Answer 13

Flocculated particles in
concentrated suspensions,
eg ointments, pastes, creams.

Flocculated suspensions have clumped particles that do not move easily, while deflocculated suspensions have particles that are spread out and can move more freely.

Question 14

Pseudoplastic examples

Answer 14

Natural, synthetic and semi-synthetic
polymers in solution,
eg tragacanth, acacia, sodium alginate,
methyl cellulose (MC),
hydroxypropylmethyl cellulose (HPMC).

Question 15

Dilatant examples

Answer 15

Rarest of the flow types. One example is
40-50% w/v suspensions of starch/water.