Particle size ophthalmic suspensions

Ophthalmic Dosage Forms. Ophthalmic preparations can be solutions, eg, eye drops, eyewashes, ointments, or aqueous suspensions (30). They must be sterile and any suspended dmg particles must be of a very fine particle size. Solutions must be particle free and isotonic with tears. Thus, the osmotic pressure must equal that of normal saline (0.9% sodium chloride) solution. Hypotonic solutions are adjusted to be isotonic by addition of calculated amounts of tonicity adjusters, eg, sodium chloride, boric acid, or sodium nitrate. 

Ophthalmic ointments usually contain petrolatum as the base. The petrolatum is sterilized by dry heat and combined with the sterile dmg powder under aseptic conditions. Ophthalmic suspensions contain very fine (- 10 ji) particle sized soHds suspended in an aqueous vehicle. The vehicle is adjusted to isotonicity and viscosity-increasing excipients, chelating agents, and surfactants also may be needed. The aqueous vehicle in these cases is generally autoclaved and mixed with sterile dmg powder asceptically (30). 

Ophthalmic, nasal, and oral inhalation preparations Appearance, color, consistency, pH, clarity (solutions), particle size and resuspendibility (suspensions, ointments), strength, and sterility... 

Hacche L, Dickason MA, Oda RM, Firestone BA. Particle size analysis for ofloxacin, prednisolone acetate, and an ophthalmic suspension containing the ofloxacin/steroid combination. Part Sci Technol 1992 10 37-47. 

Additional tests would be required for an ophthalmic suspension or other type of dosage form. Such tests might be one for particle size and one to show whether the suspension sediments can be readily dispersed on shaking to enable the correct dose to be delivered. 

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