Ophthalmic ointments and gels

B. Semisolid Dosage Forms Ophthalmic Ointments and Gels... 

Ophthalmic preparation containing combretastatin A-4 for treating diabetic retinopathy was patented [111]. The ophthalmic preparation was composed of combretastatin A-4 and other auxiliary materials acceptable for treating eye diseases. The authors claimed the preparation could be used as eye drop, ointment, and gel for treating diabetic retinopathy by inhibiting angiogenesis in a dose-dependent manner without affecting the development of retina vascular system. 

Regardless of the cause, the mainstay of treatment for dry eye is artificial tears. Artificial tears augment the tear film topically and provide relief. If a patient uses artificial tears more than four times daily, recommend a preservative-free formulation. Preservative-free formulations are also appropriate if the patient develops an allergy to ophthalmic preservatives. Artificial tears are available in gel, ointment, and emulsion forms that provide a longer duration of relief and may allow for less frequent instillation. Ointment use is appropriate at bedtime.30... 

Topically administered ophthalmic preparations can affect visual acuity. Examples are lubricating gels and ointments for dry eye, antimicrobial ointments for ocular infections, and gel-forming solutions for glaucoma. Although acuity is only slightly reduced and is only temporary, this effect can be annoying to patients and may lead to noncompliance. 

Pilocarpine is commerciaUy available in a carbomer gel vehicle.The 4% pilocarpine gel is packaged in a 3-5-g tube similar to ophthalmic ointments. A practical advantage of this sustained delivery system is the once-daily dosage regimen, with the drug usuaUy administered at bedtime. Minor side effects include superficial corneal haze, which may occur after long-term use (>8 weeks), and superficial pimctate keratitis, which can affect almost one-half the treated patients but usually resolves spontaneously. 

The topical route is almost exclusively intended for delivery of drugs to treat ophthalmic anterior segment diseases. For topical ocular administration, liquid formulations under solutions or suspensions, ointments and soluble gels are the most commonly applied because they are easy to use and do not interfere with vision. Nevertheless, these formulations are often quite ineffective due to dilution in the tear... 

Topical dosage forms such as creams, emulsions, gels, lotions, ointments, pastes, and powders may be marketed in plastic materials. Topical dosage formulations are for local (not systemic) effect and are generally applied to the skin or oral mucosal surfaces. Some vaginal and rectal creams and nasal, otic, and ophthalmic solutions may be considered for topical drug products. 

Semi-solid gel type preparations have also been developed for ophthalmic delivery as an alternative to traditional ointments, based on the effect of increasing the viscosity to prolong the retention of drug in the eye (for example, Pilopine HS gel, Alcon Laboratories, Inc.). Several types of gelling agents have been used, such as polyacrylic acid derivatives, carbomer and hypromellose. 

The exact product optimisation studies to be conducted will depend on the type of ophthalmic dosage form to be developed (liquid drops, semi-solid gel/ointment or solid device). However, the dosage form type should be clearly defined from the product design evaluation and supporting preformulation studies, to enable the formulator to focus on the most relevant product optimisation studies. 

Frequent instillation of solution or higher drug concentration is needed to achieve the desired therapeutic response. But this attempt is potentially dangerous if drug solution drained from the eye is systemically absorbed from the nasolacrimal duct. To increase precorneal residence time and ocular bioavailability, different ophthalmic delivery systems such as viscous solutions, ointments, gels, suspensions, or polymeric inserts are used. But because of blurred vision (e.g., ointments) or lack of patient compliance (e.g., inserts), these formulations have not been widely accepted. 

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