preservatives Flashcards
Chelators/Anticoagulants
Forms complex with reactive metals that aid in bacterial growth and facilitate oxidative reactions,
Inhibit bactera/mold/yeast,
eg EDTA and citrate
form a complex with blood calcium =anticoagulant
EDTA forms irreversibly
How do organic acids exhibit a preservative effect
Act by disrupting microbial metabolic pathways intracellularly, therefore most active at low, undissociated pH
Alteration of Ph affects enzyme function
eg Sorbic acid
Benzoic acid
Oxidants and antioxidants
Oxidants- source of highly reactive free radicals
eg Hydrogen peroxide
Antioxidants - reduce oxidation of active ingredient by free radicals
eg Ascorbic acid, NHT,BHA,
EDTA is added to chelate metal ions to facilitate oxidation reactions
Alcohols and parabens
Alcohols-act by dehydrating environment
eg Chlorbutanol, Phenol, Benzyl alcohol
Parabens- effective antiseptic and preservative
susceptible to decomp, risk of hypersensitivity
eg Methyl paraben, Ethyl paraben, Propyl paraben
Heavy metals act by…
Irreversibly binding to key enzymes
Organomercuric compounds
eg Thimerosal, Phenylmercuric nitrate
Polymers eg Povidone (synthetic, water soluble non-ionic that can absorb 40% own weight in water, used in WW2 as plasma expander, used stopped due to stimulation of histamine response)
Surfactants are
Bactericidal
Ionic detergents, rupture cell walls or junctions
Types of surfactants
Biguanides - 1st line DM2 agents (Metformin)
eg polyhexamethylene biguanide (PHMB)
polyaminopropyl biguanide (PAPB)
-Chlorhexidine
Alexidine
Amidoamines
eg MAPD
Quaternary Ammonium Compounds
-effective at neutral pH
-Adsorbed onto surface of glass/plastic containers
eg Benzalkonium chloride-most common in ophthalmic drops
eg Polyquaternium (quats)
What are disappearing eye drops
The are inactivated in light or different pH
Name an example of a self preserved ophthalmic drop
Moxifloxacin
