Ophthalmic Formulation

Ophthalmic Preparations

• Ophthalmic preparations are sterile, liquid, semi-solid, or solid preparations that may contain one or more active pharmaceutical ingredients intended for application to the eyelids.
• They are specialized dosage forms designed to be instilled onto the external surface of the eye, administered topically, inside (intraocular), or adjacent to the eye or used in conjunction with an ophthalmic device.

Dosage Forms

• Solutions: sterile solutions used by instillation in the eye, manufactured by dissolution of active ingredients and excipients in water, and sterilized by heat or sterilizing filtration.
• Suspensions: formulated when the drug is not sufficiently soluble, to improve stability, bioavailability, and efficacy, using a microfine form of the drug.
• Emulsions: prepared by dissolving active ingredients into an oil phase, adding emulsifying agents, and mixing with water to form a uniform oil-in-water emulsion.
• Ointments: must be sterile, non-irritating to the eye, and permit the diffusion of the active ingredient throughout the secretions bathing the eye.
• Gels: composed of mucoadhesive polymers that provide localized delivery of an active ingredient to the eye, extending the contact time of the drug with biological tissues and improving ocular bioavailability.

Formulation

• 1. Drug: includes drugs of various categories, such as antiseptic, anti-inflammatory, mydriatic, or miotic properties.
• 2. Preservative: benzalkonium chloride, used to avoid microbial contamination when the container is open.
• 3. Sterilization: done by autoclaving at 121°C for 15 minutes or by bacteria filter to avoid thermal degradation.
• 4. Isotonicity: calculated and adjusted with sodium chloride to ensure the osmotic pressure of the eye drip.
• 5. Buffer: added to maintain balance between comfort, solubility, stability, and activity of the drug.
• 6. Viscosity: influenced by the size of the drop, with methylcellulose, hydroxypropyl, and polyvinyl alcohol as common viscosity enhancers.
• 7. Container: multi-dose container (5ml, 10ml) with a sterile plastic dropper or a plastic bottle with a built-up nozzle.
• 8. Label: includes warnings, such as "Not for injection," "For external use only," and "Shake well before use" (if it's a suspension).

Advantages and Disadvantages

• Advantages: easily administered, quick absorption and effect, less visual and systemic side effects, increased shelf life, and better patient compliance.
• Disadvantages: the short time the solution stays at the eye surface, poor bioavailability, instability of the dissolved drug, and the necessity of using a preservative.

This quiz covers the formulation and preparation of ophthalmic eye drops, including the use of preservatives, sterilization methods, isotonicity, and buffering systems.