Page 7 - Laboratory manual for students FAR222 2019 20

FAR 222 Dosage Form II Laboratory Manual

OPHTHALMIC PREPARATIONS

These include solutions and occasionally suspensions (eye drops, eye lotions), semi-solids
(creams and ointments), ophthalmic injections and controlled release solid dosage forms to
be placed on the surface of the eye or implanted within it.

For each of these products sterility is an essential requirement. Eye infections have resulted
from instilled organisms (especially Pseudomonas aeruginosa). This may lead to blindness.
Particulate matter instilled into the eye may cause irritation.

Eye drops

Eye drops are sterile aqueous or oily solutions or suspensions for instillation into the eye. They
usually contain substances with antiseptic, anaesthetic, mydriatic or miotic properties, or
substances used for diagnostic purposes.

i. Eye drops for domiciliary (home) use
When the eye drops are dispensed for domiciliary use, a caution should be given to the user
to avoid contamination during use and not to use the eye drops later than four weeks after first
opening the container, unless otherwise stated in the individual monograph for the product.

ii. Eye drops for hospital use

When dispensed for use in hospitals, individual supplies of previously unopened containers
should be provided for each patient, except as described later for outpatient departments.
When both eyes are being treated, a separate container should be used for each eye. Single-
dose forms should be used in all circumstances where the dangers of infection are high.
Where single-dose forms are specified, but are not available, multiple-application units may
be used as if they were single-dose units.

In addition to the active ingredients, ophthalmic products contain a number of excipients,
including vehicles, buffers, preservatives, tonicity adjusting agents, antioxidants, viscosity
enhancers and stabilisers. It is important to ensure that all excipients selected are compatible
with the active ingredient(s) and are non-irritating to the eyes. In this section we shall consider
a few aspects of the formulation: the vehicle, adjustments to osmolarity/tonicity, buffering and
the preservation of ophthalmic solutions. Most of these aspects in formulation are similar to
the parenteral products.

i. Osmolarity/osmolality and isotonicity

Similar to parenteral products, osmolarity/osmolality is crucial for ophthalmic preparations as
lacrimal fluid has an isotonicity value similar to 0.9% sodium chloride solution or normal saline.
However, the eye can tolerate a range from 0.6% to 1.8%. Despite hypertonic solutions cause
pain and irritation, these solutions are well tolerated and cause few or no problems. The

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