Solutions and Suspensions

Ophthalmic solutions are sterile, free from foreign particles, and specially prepared for instillation in the eye. Most ophthalmic solutions are dispensed in eye dropper bottles. Patients should be shown how to properly instill the drops in their eyes, and every effort should be made to emphasize the need for instilling only one drop per administration, not two or three. When more than one drop is to be administered, wait at least five minutes between administrations. Immediately after instilling a drop on the eye, place pressure on the lacrimal sac for one or two minutes. This will reduce the rate of drug loss through this pathway.

Ophthalmic suspensions are aqueous formulations that contain solid particles. The particle size must be kept to a minimum to prevent irritation of the eye. It has been recommended that particles be less than 10 microns in size to minimize irritation to the eye. The micronized form of the drug can be used to meet this requirement. There is a tendency of the solid undissolved particles to adhere to the conjunctiva. As drug is absorbed, these solid particles will dissolve to replenish the absorbed drug. This reservoir effect increases the contact time and duration of action of a suspension compared to a solution.