Preservatives Flashcards
Preservatives
Substances added to non-sterile dosage forms
To protect them from microorganisms that are introduced inadvertently during or after preparations
(added in multiple-dose containers)
When are preservatives not needed
-When preparation is used immediately
-No water is present in the preparation
-When pH is less than 3 or greater than 9
-Presence of anti microbial ingredients in preparation
When is a preservative contradicted
Neonates
Ophthalmic solutions used for eye surgery and eye injections
Parenterals with volumes greater than 30 ml
What are alternatives when preservatives are contradicted
-prepare single dose for immediate use
-prepare limited quantity to use within short period of time
-refrigerate
-short beyond use date
Characteristics of an ideal preservatives
Effective at low concentration
Broad spectrum of activity
Chemical stability
Solubility
Compatibility with other ingredients
Non toxic
Cost
Ethyl alcohol effective concentration
Depends on pH and amount of free water
5 to 10% of the volume of compounded preparation
Benzoyl alcohol NF
-Most effective below a pH less than 5
-Minimal activity about pH 8
-Incompatible with methyl cellulose and polysorbate 80
Organic acids
Benzoic acid
Sodium benzoate
Potassium benzoate
Methyl paraben
Low concentration effective only in combination with another preservative
Propyl paraben
Most effective in combo with other preservative
Low water solubility is a problem
Where is human thimerosal usually exposed though
Human exposure primarily through sea food
Chlorobutanol
Not used in oral preparations because of its camphor-like odor and taste
