Suspensions ophthalmic

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). 

The USP has numerous requirements, e.g., ophthalmic solutions [need be] essentially free from foreign particles, suitably compounded and packaged for instillation into the eye, or ophthalmic suspensions [need contain] solid particles dispersed in liquid vehicle intended for application to the eye [1]. Ophthalmic suspensions are required to be made with the insoluble drug in a micronized form to prevent irritation or scratching of the cornea. A finished ophthalmic ointment must be free from large particles and must meet the requirements for leakage and for metal particles under ophthalmic ointments . These and other requirements will be discussed further in subsequent sections. 

Suspension. If the drug is not sufficiently soluble, it can be formulated as a suspension. A suspension may also be desired to improve stability, bioavailability, or efficacy. The major topical ophthalmic suspensions are the steroid anti-inflammatory agents prednisolone acetate, dexamethasone, fluorometholone, and rimex-olone. Water-soluble salts of prednisolone phosphate and dexamethasone phosphate are available however, they have a lower steroid potency and are poorly absorbed. 

An ophthalmic suspension should use the drug in a microfine form usually 95% or more of the particles have a diameter of 10 pm or less. This is to ensure that the particles do not cause irritation of the sensitive ocular tissues and that a uniform dosage is delivered to the eye. Since a suspension is made up of solid particles, it is at least theoretically possible that they may provide a reservoir in the cul-de-sac for slightly prolonged activity. However, it appears that this is not so, since the drug particles are extremely small, and with the rapid tear turnover rate they are washed out of the eye relatively quickly. 

Oxytetracycline preparations for oral administration should contain not less than 90% or not more than 120% [i] or not less than 90% and not more than 110% [2], of the labeled amount. For ointment, the requirements are not less than 90.0% and not more than 115% (for oxytetracycline HC1 and Hydrocortisone ointment, or 120% for other ointment. For ophthalmic suspension mixture with hydrocortisone acetate, its content should contain not less than 90% and not more than 110% [1]. 

A physician prescribes an ophthalmic suspension to contain 100 mg of cortisone acetate in 8 mL of normal saline solution (NSS). The pharmacist has a 2.5% suspension of cortisone acetate in NSS. How many milliliters of this and how many milliliters of NSS should be used in preparing the medication order ... 

Ophthalmic suspensions mix with tears less rapidly and remain in the cul-de-sac longer than solutions. 

Topical 5% ophthalmic suspension Nystatin (generic, Mycostatin)... 

Capsules 25mg and 50mg Time Release Capsules 75mg Injection l.Omg/ml Ophthalmic Suspension lOmg/ml Oral Suspension lOmg/ml Suppositories 50mg and lOOmg... 

Suspensions are commonly formulated by dispersing micronized drag powder (< 10 pm in diameter) in a suitable aqueous vehicle. Ophthalmic suspensions, particularly for the steroids, are thought to be acceptable as delivery systems since it is assumed that drag particles persist in the conjunctival sac giving rise to a sustained release effect. However, suspensions have a disadvantage that the concentration of dissolved drags cannot be manipulated due to their relative insolubility in the vehicle. 

According to Davies [174], topical ophthalmic suspensions have a number of limitations compared to solutions. They need to be adequately shaken before use to ensure correct dosing, a process which can result in poor patient compliance. In addition, they need to be sterilized, which may cause physical instability of the formulation. Furthermore, the amount of drug required to achieve only a moderate increase in bioavailability is very high, rendering suspensions expensive in terms of their production costs [175],... 

Use. Usually applied as a 0.025% cream or ointment and is also available as a 0.1% ophthalmic suspension. 

Figure 4-1 Typical prescription format. (A) Ophthalmic suspension. (B) Ophthalmic ointment.

Natamycin (pimaricin) Natacyn- 5% ophthalmic suspension 5% natamycin is the treatment of choice for treating filamentous fungal keratitis. Natamycin is more effective than itraconazole for treating Fusarium keratitis but is not effective in treating deep stromal infections. 

Miconazole Topical 1% ophthalmic suspension 1 drop qlh Subconjunctival 10 mg/0.5 ml Topical side effects of burning, itching, tearing Not commercially available both topical and subconjunctival formulations must be compounded fV brand discontinued in United States Good ocular penetration with topical and subconjunctival use Toxic conjunctival necrosis may occur with subconjunctival use Pregnancy category C lactation safety unknown... 

Miconazole comes in topical (1% ophthalmic suspension), subconjunctival depot (10 mg/0.5 ml), and oral (200-400 mg/day) formulations but is not commercially available now in any of these formulations. Miconazole is relatively broad spectrum and active against most yeast but has variable coverage of Aspergillus and Fusarium. Miconazole is generally well tolerated with topical and subconjunctival administration, but cases of corneal toxicity have been reported. 

Itraconazole is a broad-spectrum synthetic triazole that has good oral bioavailability and is less toxic than amphotericin B and ketoconazole.The solution has better bioavailability than the capsule and provides higher plasma concentration levels. Compared with fluconazole and ketoconazole, itraconazole penetrates all ocular tissues poorly when orally administered. Itraconazole can be used as a 1% ophthalmic suspension but is not very effective in treating severe fungal keratitis. 

Dexamethasone is available as an alcohol or phosphate derivative in the fiarm of a 0.1% ophthalmic suspension or... 

Like fluorometholone, rimexolone lacks a hydroxyl group in the 21 position. Available as a 1% ophthalmic suspension (Vexol) (see Table 12-4), it has FDA approral for treatment of uveitis and postoperative inflammation. 

Lane SS, Modi SS, Lehmann RP, Holland EJ. Nepafenac ophthalmic suspension 0.1% for the prevention and treatment of ocular inflammation associated with cataract surgeryj Cataract Refract Surg 2007 33 53-58. 

Netland PA, Leahy C, Krenzer KL. Emedastine ophthalmic solution 0.05% versus levocabastine ophthalmic suspension 0.05% in the treatment of aUergic conjunctivitis using the conjunctival aUergen chaUenge model. Am J Ophthalmol 2000 130 717-723. 

Secchi A, Ciprandi G, Leonard A, et al. Safety and efficacy comparison of emedastine 0.05% ophthalmic solution compared to levocabastine 0.05% ophthalmic suspension in pediatric subjects with allergic conjunctivitis. Acta Ophthalmol Scand 2000 78 42-47. 

Fluorometholone, USP. Fluoromctholone. 9-lluoio-11 p. 17-dihydroxy-6a-mcthylpregn-4-cne-3.20-dione(Fluor-Op. FML). lacks the typical C2I hydroxyl group of glucocorticoids and is used exclusively in ophthalmic products. The 17-acctatc of fluorometholone is also used as an ophthalmic suspension (Flarex). 

The use of the povidone in sugar-coating suspensions is described in Section 2.4.4 and their use in ophthalmic suspensions in Section 2.4.7. 

Povidone can also be used as a sedimentation stabilizer in ophthalmic suspensions. Mefenamic acid suspension is a typical example [492]. 

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