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Ophthalmic Preservatives and Dry Eye
IN CHRONIC EYE DISEASES, Such as keratoconjunctivitis sicca,
ophthalmic medications need to be used regularly and continuously to
be effective. Patients with KCS may need to use ophthalmic solutions
indefinitely. Frequent use of preservative-containing artificial tears
may aggravate KCS.
Frequent use of preserved ophthalmic solutions leads to:
- Higher incidence of epithelial damage.
- Disruption of the lipid layer of the tear film
.
- Increase in the corneal permeability
- Decrease in the activity of lysozyme in the
tear fluid
- Increased sensitization with risk of ocular allergy.
- Bulbous keratopathy.
Preservatives’ benefits
Most of ophthalmic products are chemically preserved. In fact, the U.S.
Food and Drug Administration and the U.S. Pharmacopoeia mandate the
use of preservatives for all multidose topical ophthalmic medications.
Preservatives provide antimicrobial activity in the container and prolong
shelf life by preventing the decomposition of the active drug. Research
has shown that preservatives are necessary in multidose containers,
because bacterial contamination occurs with the use of the drug at least
twice daily for one or two weeks.
Types of ocular preservatives
Detergent preservatives and oxidative preservatives. Detergent preservatives
alter cell membrane permeability and lyse cytoplasmic content of bacteria
such as benzalkonium chloride. Oxidative preservatives are able to penetrate
cell membranes and interfere with cell functions of the bacteria such
as sodium perborate .
At low level, oxidative preservatives have an advantage over detergent
preservatives because they can provide enough activity against microorganisms
while having only negligible toxicity on eukaryotic cells. This is because
many microorganisms do not have the ability to cope with oxidative stress.
By comparison, mammalian cells are equipped with antioxidants, oxidases
and catalases to neutralize the effect of a low-level oxidant.
http://www.revophth.com/2001/june/cme0601_article.htm
click here to download Review on Ophthalmic preservatives.
Ophthalmic
Preservatives and Dry Eye
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