Preservatives/preservation, ophthalmic products/drugs

Ophthalmic products have to be manufactured sterile and be free from micro-organisms. Once opened, the sterility of a multidose product must be maintained during its period of use. This is usually required for at least 4 weeks, after which the product is discarded. If the drug itself does not possess antimicrobial properties, then an antimicrobial preservative must be included in the formulation to ensure that any micro-organisms accidentally introduced during use are destroyed. 

Inactive ingredients may be found in some preparations. Examples of these drugs include preservatives, antioxidants, which prevent deterioration of the product, and drugs that slow drainage of the drug from the eye into the tear duct. Examples of the types of eye preparations are found in the Summary Drug Table Select Ophthalmic Preparations. 

Chiral alcohols are useful starting materials for the synthesis of various biologically active compounds. The need for enantiomerically pure drugs and agrochemicals has increased in recent years [13]. Derivatives of enantiopure 1-phenylethanol are important chiral building blocks, which can be used as synthetic intermediates for the production of pharmaceuticals, fine-chemicals agrochemicals, and natural products. In particular (R)-1-phenylethanol is in widespread use as an ophthalmic preservative, an inhibitor of cholesterol intestinal adsorption, a solvatochromic dye, a fragrance, and so on. 

Surfactants may be included in an ophthalmic suspension to disperse the drug effectively during manufacture and in the product during use. Non-ionic surfactants are generally preferred because they tend to be less toxic. The level of surfactant included in the formulation should be carefully evaluated, as excessive amounts can lead to irritation in the eye, foaming during manufacture and upon shaking the product, or interactions with other excipients. The most likely interaction is with the preservative. For example, polysorbate 80 interacts with chlorobutanol, benzyl alcohol, parabens and phenyl ethanol and may result in a reduced preservative effectiveness in the product. 

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