Composition of Eye Drops
Besides medicines, eye drops may contain a number of additional material to maintain potency and prevent decomposition. Additional ingredients include:

Preservative
There is material to prevent the development of microorganisms that may be present during the use of eye drops. The most used preservative is phenyl mercury nitrate, phenyl ethyl alcohol and benzalkonium chloride.

Isotonicity with lacrimal secretions
NaCl is normally used to reach the osmotic pressure within their ophthalmic solution.

Oxidation of Drugs
Many eye medication immediately oxidized and usually in some cases including a reducing agent. Metasulfit sodium in concentrations of 0.1% is generally used for this purpose.


Hydrogen Ion Concentration
Need for stability of the hydrogen ion concentration, and several buffers have been described. Sodium citrate is used in ophthalmic phenylephrine.

Chelating material
When the ions and heavy metals can cause decomposition of the drug in a solution of the material used chelators that bind ions in organic complexes, will provide protection. Na2EDTA, one of the most well known as chelators.

Viscosity
To prepare the viscous solution by giving the action a long time in solution with a fixed eye contact longer on the surface of the eye, thickeners can be used, methylcellulose 1% was used for this purpose.

Eye Fluid pH
Lacrimal secretions have a pH value between 7.2 to 7.4 and have high capacity of buffering. As a result, the eye can tolerate a solution having a pH value of 3.5 to 10, they not buffered strongly because liquid eye will quickly improve the value of the normal pH of the eye.

Eye Preparations pH
Solution of normal lacrimal pH 7.4 with a range from 5.2 to 8.3. It can still be tolerated by the eye solution with this pH range, due to (1) small volume of solution, (2) buffer liquid eyes, and (3) increased production of tears. pH of the solution of the eyes should be between 4.5 and 9.

Container
Containers for the solution of the eyes. Eye solution should be used in small units, is never greater than 15 ml and preferably smaller. 7.5 ml bottle is a nice size to use eye solution. The use of small containers to shorten the treatment time will be kept by the patient and minimize the amount of exposure to contamination.

Eye solution prepared continuously packed in the container drops (droptainers) polyethylene or drops in a glass bottle. To maintain sterility of the solution, the container must be sterile. Polyethylene container sterilized with ethylene oxide, while the glass dropper can be wrapped and autoclaved. Commercially prepared single dose units with a volume of 0.3 ml or less packed in sterile polyethylene tubes and sealed by heating.

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