Lec 8- Solutions and preservatives Flashcards
Solution
A stable, homogenous one-phase system consisting of two or more components
Solvent
Dispersion phase or vehicle
Solute
Dissolved as small molecules or ions in the solvent
What are the advantages of pharmaceutical solutions over solid dose forms?
- Ease of swallowing
- Increased absorption
- Even dosage
- Flexible dosing
- Gastric irritation reduced
What are the disadvantages of pharmaceutical solutions?
- Bulky containers
- Hydrolysis or oxidation of active ingredients
- Contamination
- Accuracy of dosage, need measure
- Unpleasant taste difficult to mask
Aqueous solvents
- Relatively cheap and available
- Palatable
- Non-toxic
- Non-irritant for topical use
- Polar so dissolves salts and ions
Linctus
A liquid oral preparation used for a demulcent, expectorant or sedative purpose
-> treatment of a cough
- sipped slowly and allowed to trickle down the throat in an undiluted form.
- viscous solutions which contain sugars
Syrup
A concentrated viscous solution containing one or more sugar components
- chiefly sucrose at conc at least 45%
- flavoured syrups provide a sweet vehicle to mask taste of nauseous medicaments
What does an antitussive do?
Eg codeine linctus
- Works against a cough
- Acts on the central and peripheral nervous systems to suppress cough reflex
- Not desirable with a productive cough
Note: codeine is sedating -> may cause drowsiness and increase effects of alcohol
Elixir
Eg. paediatric paracetamol elixir
A liquid oral preparation that usually contains potent or unpleasant tasting drugs
- formulation is clear and generally contains high proportion of sweeteners and non aq solvents like alcohol, glycerin or popylene glycol
Enema
An oily or aq solutions which is administered rectally
- used to treat conditions such as constipation or ulcerative colitis
- used in x-ray examination of the lower bowel and for systemic effects
eg. diazepam in epilepsy and febrile convulsions
Non aq solutions
- Non toxic
- Non irritant
- Non sensitizing
- Cost effective
- Stable
- Compatible with medicament
Examples of non aq solutions
- Alcohol
- Propylene glycol
- Glycerol
- Oils
Solubility
The saturation solubility or solubility of a chemical in a solvent
- max conc of a solution which may be prepared at a given temperature
Dissolution
Process of dissolving
- improve dissolution by increasing SA and decreasing particle size
Solution additives (excipients)
- added to improve palatability- taste, feel and appearance
Stabiliser/ buffer
An antioxidant to prevent oxidation
- ascorbic acid, citric acid
- tasteless, ordourless and non-toxic
Colourants
Enhance appearance- match flavour
- distictive colour for identification of strength
Flavourants
improve tastye
Children enjoy fruit or sweet flavours
- antacid-> peppermint
Anti-microbial preservative
Kills micro organisms or inhibits their groqth and replication
Disinfectant perservative
To eliminate many or all pathogenic micro organisms
Antiseptic preservative
Inhibits growth and reproduction of organisms
Preservative
Chemical or other agent that reduces the rate of decomposition of a substance
Ideal properties of a preservative
- Non-toxic, non allergenic
- Bactericidal rather than bacteriostatic
- Active against a wide range of micro organisms
- Inexpensive
- High resistance to attack by micro organisms
- Stable under wide range of storage conditions
- Free from unpleasant odour
- Unaffected by other formulation ingredients
