OPHTHALMIC PREPARATION(formulation and evaluation)

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Ophthalmic preparations, advantages, disadvantages, formulation, evaluation, routes of delivery,

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Mohd Irshad Reza 13SMAS102075 B Pharm (3 rd yr) GALGOTIAS UNIVERSITY

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Definition : Ophthalmic preparations (eye preparations) are sterile, liquid, semi-solid, or solid preparations that may contain one or more active pharmaceutical ingredient intended for application to the conjunctiva, the conjunctival sac or the eyelids. They are specialized dosage forms designed to be instilled onto the external surface of the eye (topical), administered inside (intraocular) or adjacent ( periocular ) to the eye or used in conjunction with an ophthalmic device. The most commonly employed ophthalmic dosage forms are solutions, suspensions, and ointments. The newest dosage forms for ophthalmic drug delivery are: gels, gel-forming solutions, ocular inserts , intravitreal injections and implants.

ADVANTAGE::

ADVANTAGE: They are easily administered by the nurse They are easily administered by the patient himself. They have the quick absorption and effect. less visual and systemic side effects. increased shelf life. better patient compliance.

DISADVANTAGES: :

DISADVANTAGES: The very short time the solution stays at the eye surface. Its poor bioavailability. The instability of the dissolved drug. The necessity of using preservative.

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Drugs used in the eye :- Miotics e.g. pilocarpine Hcl Mydriatics e.g. Atropine Cycloplegics e.g. Atropine Anti- inflammatories e.g. corticosteroids Anti- infectives (antibiotics, antivirals and antibacterials ) Anti- glucoma drugs e.g. pilocarpine Hcl Adjuncts e.g. Irrigating solutions Diagnostic drugs e.g. sodiumfluorescein Anesthetics e.g. Tetracaine

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Anatomy and Physiology of the Eye:

Formulation::

Formulation: 1)Drug 2)Preservative 3)Sterilization 4) I sotonicity 5)Buffer 6)Viscosity 7)Container 8)Label

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1) Drugs- T hese contains drugs of various categories including antiseptic, anti-inflammatory agent, mydriatic or miotic properties 2) Preservative- Eye drop should be sterile and should contain preservatives to avoid microbial contamination when container is open. The preservative for ophthalmic use includes benzalkonium chloride, chlorbutanol , phenylmercuric acetate, phenylmercuric nitrate etc.,

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3)Sterilization- Eye drops are sterilized by autoclaving at 121°C for 15 minutes or by bacteria filter to avoid thermal degradation for example- preservative chlorbutanol hydrolyzes at high temperature 4) Isotonicity - All the solutes including drug contribute to the osmotic pressure of the eye drip, therefore isotonicity of the formula should be calculated and it is adjusted with sodium chloride, for example sodium chloride 0.9% and boric acid 1.9& are iso -osmotic

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5)Buffer- the buffer should be added to maintain balance between comfort, solubility, stability and activity of drug. For example the hydrolysed chlorbutanol forms hydrochloride acid making the drop acidic. Whereas certain drug like pilocarpine hydrochloride are acidic 6)Viscosity- the size of the drop and its residence in eye depends on viscosity of eye drops. Methyl cellulose, hydroxypropyl methycellulose and polyvenyl alcohol are common viscosity inhancer

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7) Container- the commonly used container for ophthalmic solutions or suspension is multi-dose container(5ml, 10ml). Glass container is supplied with sterile plastic dropper. Plastic bottles are with built up nozzle. 8)Label- Not for injection. For external use only. Shake well before use (if it is suspension)

DOSAGE FORMS APPLIED TO THE EYE :

DOSAGE FORMS APPLIED TO THE EYE Topical Administration Solutions Suspension Emulsion Ointment Gel Perfusion Spray Inserts Intraocular drug delivery Intraocular injection Implant Iontophoresis Liposome Niosome

Drug delivery routes:

Drug delivery routes

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Solutions Ophthalmic solutions are sterile solutions intended for instillation in the eye. Included in this dosage form category are solid preparations that, when reconstituted according to the label instructions, result in a solution Solutions are Manufactured by dissolution of the active ingredients and a portion of the excipients into all portion of water . The sterilization of this solution done by heat or by sterilizing Filtration through sterile depth or membrane filter media Into a sterile receptacle. This sterile solution is then mixed with the additional required Sterile components such as viscosity –imparting agents, Preservatives and so and the solution is brought to final Volume with additional sterile water

Disadvantages of eye solutions: :

Disadvantages of eye solutions: The very short time the solution stays at the eye surface.The retention of a solution in the eye is influenced by viscosity. Its poor bioavailability (a major portion i.e. 75% is lost via naso lacrimal drainage). Examples of topical eye solutions : Atropine sulphate eye drops. Pilocarpine eye drops . Silver nitrate eye drops. Zinc sulphate eye drops.

suspensions:

suspensions If the drug is not sufficiently soluble, it can be formulated as a suspension. A suspension may also be desired to improve stability, Bioavailability ,and efficacy. The major topical ophthalmic suspensions are the steroid anti-inflammatory agents. An ophthalmic suspension should use the drug in a microfine form; usually 95% or more of the particles have a Diameter of 10 µm or less.

Examples of eye suspension:

Examples of eye suspension Prednisolone acetate suspension. Besifloxacin suspension. Blephamide suspension. Fluorometholone suspension

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Emulsions Topical ophthalmic emulsions generally are prepared by dissolving or dispersing the active ingredient(s) into an oil phase, adding suitable emulsifying and suspending agents and mixing with water vigorously to form a uniform oil-in-water emulsion. Each phase is typically sterilized prior to or during charging into the mixing vessel.

Ointments:

Ointments Ophthalmic ointments must be sterile The ointment base selected for an ophthalmic ointment must be nonirritating to the eye and must permit the diffusion of the active ingredient throughout the secretions bathing the eye. Ophthalmic ointments have a longer ocular contact time when compared to many ophthalmic solutions One disadvantage to ophthalmic ointments is the blurred vision that occurs as the ointment base melts and is spread across the lens.

Example of ophthalmic ointment:

Example of ophthalmic ointment Chloramphenicol ointment. Tetracycline ointment. Hydrocortisone ointment.

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Gels Ophthalmic gels are composed of mucoadhesive polymers that provide localized delivery of an active ingredient to the eye. Such polymers have a property known as bioadhesion meaning attachment of a drug carrier to a specific biological tissue. These polymers are able to extend the contact time of the drug with the biological tissues and thereby improve ocular bioavailability

Perfusion:

Perfusion Continuous and constant perfusion of the eye with drug solutions can be achieved by the use of ambulatory motor driven syringes that deliver drug solutions through fine polyethylene tubing positioned in the conjunctival sac This system allows the use of a lower drug concentration than used in conventional eye-drops, yet will produce the same potency. Side effects are reduced and constant therapeutic action is maintained

Sprays:

Sprays Spray systems produce similar results to eye-drops in terms of duration of drug action and side effects. Sprays have several advantages over eye-drops: a more uniform spread of drug can be achieved precise instillation requiring less manual dexterity than for eye-drop administration and is particularly useful for treating patients with unsteady hand movements contamination and eye injury due to eye-drop application are avoided spray delivery causes less reflex lacrimation . Can be used by patients who have difficulty bending their neck back to administer drops.

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Ophthalmic inserts are defined as sterile solid or semisolid preparations, with a thin, flexible and multilayered structure, for insertion in the conjunctival sac.

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Advantages: Increasing contact time and improving bioavailability. Providing a prolong drug release and thus a better efficacy. Reduction of adverse effects. Reduction of the number administrations and thus better patient compliance. FOR EXAMPLE Lacrisert is a sterile ophthalmic insert use in the treatment of dry Eye syndrome and is usually recommended for patients unable to obtain symptomatic relief with artifical tear solutions. The insert is composed of 5 mg of Hydroxypropyl cellulose in a rod-shaped form about 1.27 mm diameter by about 3.5 mm long.

Intraocular Dosage Forms :

Intraocular Dosage Forms They are Ophthalmic products that introduced into the interior structures of the eye primarily during ocular surgery. Intraocular Injections The ophthalmologist use available parental dosage forms to deliver Anti-infective, corticosteroids, and anesthetic products to achieve higher therapeutic concentrations intraoculary than can ordinarily Be achieved by topical or systemic administration. FDA approved intraocular injection include miotics , viscoelastics and an antiviral agent for intravitreal injection.

Intravitreal implant :

Intravitreal implant An intravitreal sterile implant containing ganciclovir or antineoplastic agents is a tablet of ganciclovir with Magnesium stearate and is coated to retard release with Polyvinyl alcohol and ethylene vinyl acetate polymers. Such that the device when surgically implanted in the Vitreous cavity release drug over a 5 to8 month period .

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Ocular iontophoresis : Iontophoresis is the process in which direct current drives ions into cells or tissues. If the drug molecules carry a positive charge, they are driven into the tissues at the anode; if negatively charged, at the cathode. Ocular iontophoresis offers a drug delivery system that is fast, painless, safe, and results in the delivery of a high concentration of the drug to a specific site. Iontophoresis is useful for the treatment of bacterial keratitis , Iontophoretic application of antibiotics may enhance their bactericidal activity and reduce the severity of disease

Liposomes:

Liposomes Liposome's are microscopic and submicroscopic vesicles consists of one or more concentric sphere of Lipid bilayers separated by Water or aqueous buffer compartments

Niosomes:

Niosomes They are non-ionic surfactant based vesicles , formed from the self assembly of non-ionic amphiphiles in in aqueous media resulting in closed bilayer structures

Advantages of Niosomes and liposomes :

Advantages of Niosomes and liposomes Sustained release of active compounds. Protect drugs from degradation Biocompatible, biodegradable and non- immunogenic. can entrap both hydrophilic and lipophilic drugs The bilayer can efficiently penetrate the cornea of the eye. They have low toxicity because of their non-ionic nature

Evaluation tests:

Evaluation tests Metal Particles This test is required only for ophthalmic ointments. The presence of metal particles will irritate the corneal or conjunctival surfaces of the eye. It is performed using 10 ointment tubes. The content from each tube is completely removed onto a clean 60 - mm - diameter Petri dish which possesses a flat bottom. The lid is closed and the product is heated at 85 ° C for 2 h. Once the product is melted and distributed uniformly, it is cooled to room temperature. The lid is removed after solidification. The bottom surface is then viewed through an optical microscope at 30× magnification

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The viewing surface is illuminated using an external light source positioned at 45 ° on the top. The entire bottom surface of the ointment is examined, And the number of particles 50 μm or above are counted using a calibrated eyepiece micrometer. The USP recommends that the number of such particles in 10 tubes should not exceed 50, with not more than 8 particles in any individual tube. limits are not met, the test is repeated with an additional 20 tubes. In this case, the total number of particles in 30 tubes should not exceed 150, and not more than 3 tubes are allowed to contain more than 8 particles .

Leakage test ::

Leakage test : This test is mandatory for ophthalmic ointments, which evaluates the intactness of the ointment tube and its seal. Ten sealed containers are selected, and their exterior surfaces are cleaned. They are horizontally placed over absorbent blotting paper . Maintained at 60 ± 3 ° C for 8 h. The test passes if leakage is not observed from any tube. If leakage is observed, the test is repeated with an additional 20 tubes. The test passes if not more than 1 tube shows leakage out of 30 tubes .

Sterility Tests ::

Sterility Tests : Ophthalmic semisolids should be free from anaerobic and aerobic bacteria and fungi. Sterility tests are therefore performed by the: 1. Membrane filtration technique . 2. Direct - inoculation techniques. In the Membrane filtration method : A solution of test product (1%) is prepared in isopropyl myristate and allowed to penetrate through cellulose nitrate filter with pore size less than 0.45 μ m. If necessary, gradual suction or pressure is applied to aid filtration.

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The membrane is then washed three times with 100 - mL quantities of sterile diluting and rinsing fluid and transferred aseptically into fluid thioglycolate (FTG) and soybean – casein digest medium (SBCD) . The membrane is finally incubated for 14 days. Growth on FTG medium indicates the presence of anaerobic and aerobic bacteria. Soybean casein digest medium indicates fungi and aerobic bacteria Absence of any growth in both these media establishes the sterility of the product.

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In the Direct - inoculation technique : 1 part of the product is diluted with 10 parts of sterile diluting and rinsing fluid with the help of an emulsifying agent Incubated in Fluid thioglycolate (FTG) and soybean – casein digest medium (SBCD) media for 14 days .

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In both techniques, the number of test articles is based on the batch size of the product. If the batch size is less than 200 the containers, either 5% of the containers or 2 containers (whichever is greater) are used. If the batch size is more than 200, 10 containers are used for sterility testing .

References:

References Dispensing for pharmaceutical by Cooper and gunn’s pg: 634-661 Modern dispensing pharmacy : N K Jain pg: 13.3-14.9 Text of pharmaceutical formulation : B.M Mithal pg: 268-278

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