Patent Publication Number: US-2012034278-A1

Title: Ophthalmic preparation containing menthyl ester of indomethacin

Description:
RELATED APPLICATIONS 
     This application claims priority from filed U.S. Provisional Patent Application Ser. No. 60/733,756, entitled, “Ophthalmic Preparation Containing Menthyl Ester of Indomethacin”, filed Nov. 7, 2005. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to an ophthalmic pharmaceutical preparation comprising menthyl ester of indomethacin and to the use of said preparation for the treatment of inflammation of the eye. 
     BACKGROUND OF THE INVENTION 
     Indomethacin [1-(4-Chlorobenzoyl)-5-Methoxy-2-methyl-1H-indole-3-acetic acid] has superior anti-inflammatory, analgetic and antipyretic activities and is used in the form of capsules (Indocin®) for treatment of systemic inflammatory diseases (arthritis, muscle pain, tendonitis, etc.). Sodium salt of indomethacin may be injected intravenously or used for treatment of inflammatory conditions in the eye (Indocollyre®). 
     Indomethacin is practically insoluble in water. Solubility in water media improves with increased pH, but the produced solution of indomethacin salt is very unstable and degrades quickly, forming inactive compounds. Additionally, either indomethacin itself or sodium salt of indomethacin are highly irritating to mucous surfaces, causing stinging and burning sensations. Furthermore, extended use almost definitely produces ulceration. 
     In order to decrease such irritation, different derivatives of indomethacin have been explored. Multiple esters, amides, Mannich bases, and some other hydrolysable compounds were synthesized. Such modification usually leads to a decrease in ulcerogenicity and a decrease of local irritation, along with an increase in lipophilicity. In some cases, such modification has resulted in modified cyclooxygenase inhibition selectivity. For instance, indomethacin is a non-selective COX-1/COX-2 inhibitor, while many of its esters and other derivatives are described as selective COX-2 inhibitors. [U.S. Pat. No. 6,306,890 (“Esters Derived from Indolealkanols and Novel Amides Derived from Indolealkylamides that are Selective COX-2 Inhibitors”) and U.S. Pat. No. 6,762,182 (“Converting COX Inhibition Compounds that are not COX-2 Selective Inhibitors to Derivatives that are COX-2 Selective”), both to Kalgutkar et al.]. 
     Different formulations of NSAIDs are used for the treatment of ophthalmic inflammation conditions. For example, Diclofenac sodium 0.1% (Voltaren® ophthalmic, Novartis), Bromfenac 0.09% (Xibrom®, ISTA/Senju Pharmaceuticals), Flurbiprofen sodium 0.03% (Ocufen®), Allergan, Bausch &amp; Lomb), Indomethacin sodium 0.1% (Indocin® Ophthalmic, Merck, Indocollyre®, Chauvin) and 1.0% Indomethacin sodium (Indoptol®, Merck Sharp &amp; Dohme), and Ketorolac tromethamine 0.5% (Acular®, Allergan) for ophthalmic applications are manufactured and marketed in many countries. 
     Due to the chemical structure and pharmacological properties of the NSAIDs, their application can cause local irritation, burning and itching sensations, and may delay wound healing. In some cases, use of NSAIDs may cause superficial punctate keratitis. [Salva P. et al., 1999; Scuderi B. et al., 2003; Mccarey B. et al., 1995; Stroobants A. et al., 2000; Diestelhorst M. et al., 1996]. 
     New ophthalmic vehicles and delivery systems have been introduced in the last decade which improve the tolerability and increase the efficacy of ocular treatments. Bioadhesive inserts and gels, nanoparticles, nanocapsules, niosomes, liposomes, and microemulsions have been extensively investigated. [U.S. Pat. No. 5,496,811 (“Submicron Emulsions as Ocular Drug Delivery Vehicles”) to Aviv H. et al.; U.S. Pat. No. 5,364,632 (“Medicinal Emulsions”) to Benita S, and Levy M.; U.S. Pat. No. 5,171,566 (“Flurbiprofen Derivative Ophthalmic Preparation”); and U.S. Pat. No. 4,613,505 (“Ester of Flurbiprofen and Emulsion Containing the Same”), both to Mizushima Y. et al.]. 
     Colloidal ophthalmic compositions show improved tolerance and better transport properties for incorporated drugs [Aggarwal D. et al., 2005; Mainardes R. et al., 2005; De T K et al., 2004; Calvo P. et al., 1996]. 
     Menthol can improve the penetration of indomethacin across the skin in mixtures of indomethacin and menthol by increasing permeability of the skin. Menthol is irritative to the eye, however. Therefore, a mixture of menthol and indomethacin at concentrations high enough to show improved penetration of indomethacin would likely be too painful to the eye to permit a mixture of indomethacin and menthol to feasibly be used in an ophthalmic preparation. 
     Another disadvantage of indomethacin is that it is unstable at pH greater than 6.0. As such, indomethacin is unstable in the body pH of approximately 7.4. 
     Due to the limitations of current ophthalmic pharmaceutical compositions which comprise indomethacin or sodium salt of indomethacin, there is a need for an improved ophthalmic pharmaceutical composition of indomethacin that shows both enhanced stability, and lesser negative side effects. 
     SUMMARY OF THE INVENTION 
     The inventors have developed ophthalmic pharmaceutical compositions which comprise an ester of indomethacin, such as menthyl ester of indomethacin (MEI). The compositions of the invention show significantly decreased negative side effects and improved stability as compared to other ophthalmic pharmaceutical compositions comprising indomethacin or indomethacin salts. The compositions are more stable at higher pH. These compositions also show enhanced penetration through biological membranes such as through the skin and through the eye. 
     Accordingly, in one embodiment, the MEI is prepared by esterification of indomethacin with menthol. The resulting compound is then purified by crystallization. 
     In another embodiment, the purified MEI can be formulated into a colloidal dispersion. 
     In another embodiment, the purified MEI can be formulated into a suspension. 
     In another embodiment, MEI can be incorporated into a micellar preparation. 
     In another embodiment, clear solutions of MEI can be prepared by mixing MEI into a water-based solution. 
     In yet another embodiment, MEI can be incorporated into an emulsion. 
     In yet another embodiment, MEI can be incorporated into an emulsion, where the particles of MEI are of submicron size. In one embodiment, the particles could be from 10-1000 nm in diameter. In another embodiment they could be from 15-500 nm in diameter. It will appreciated that other size ranges for the particles of MEI may also work. 
     In yet another embodiment, MEI can be incorporated into a bioadhesive suspension. 
     In still yet another embodiment, MEI can be incorporated into a bioadhesive emulsion. 
     In still yet another embodiment, MEI can be incorporated into a gel. 
     In still yet another embodiment, the MEI can be incorporated into a gel comprising poloxamer. Poloxamer is a synthetic block copolymer of ethylene oxide and propylene oxide. 
     In yet another embodiment, a pharmaceutically effective amount of MEI can be applied to an eye to treat inflammation of the eye. Inflammation can be caused by many factors, including, but not limited to, infection, surgery, burn, irritation, injury or other trauma. 
     Thus the invention provides a method of ophthalmic treatment, including prophylactic treatment, by administering to an eye (wherein the eye is inflamed or may become inflamed) an effective amount of the pharmaceutical composition of the invention comprising a menthyl ester of indomethacin. In one embodiment the effective dose applied is 0.05-5 mg/day/eye. 
     As such, in one embodiment, the invention provides a pharmaceutical composition comprising a menthyl ester of indomethacin and a pharmaceutically acceptable carrier. In one embodiment, the pharmaceutical composition is an ophthalmic pharmaceutical composition. In one embodiment, the pharmaceutical composition is in the form of a colloidal dispersion. In another embodiment the colloidal dispersion is a suspension, emulsion, or microemulsion. In another embodiment the composition comprises micelles, nanoparticles, nanocapsules, niosomes and/or liposomes comprising menthyl ester of indomethacin. In one embodiment the pharmaceutical composition is a lotion, cream, ointment or solution in non-irritative vehicle. In another embodiment, the amount of menthyl ester of indomethacin in the composition is 0.05-5% (w/w). 
     In one embodiment, the MEI can be applied topically to the eye. 
     In one embodiment, the MEI can be applied topically to the eye by way of eye drops. 
     Other features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from reading the detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates the reaction of indomethacin with L-menthol to form the menthyl ester of indomethacin. 
         FIG. 2  is a graph illustrating the pharmacokinetics of MEI in Wistar rats after intraperitoneal IP) administration (20 mg/kg, Example 6) as described in Example 11. 
         FIG. 3  is a graph illustrating the comparative anti-inflammatory activity of indomethacin and MEI in a carrageenan paw edema model (rats, n=4) as described in Example 12. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     Menthyl ester of indomethacin (MEI) was prepared by esterification of indomethacin with menthol. The method of esterification would be apparent to the skilled person working in synthetic chemistry. Suitable methods include condensation in the presence of an acidic catalyst or using a coupling agent, such as carbodiimide, but it will be appreciated that other methods of esterification known to those skilled in the art may be used. The reaction of menthol (2-isopropyl-5-methylcyclohexanol) and indomethacin [1-(4-Chlorobenzoyl)-5-Methoxy-2-methyl-1H-indole-3-acetic acid] yields MEI. The reaction between menthol and indomethacin is depicted in  FIG. 1 . Any crystalline or amorphous form of indomethacin can be used. Furthermore, any complex, including, but not limited to hydrates, hemihydrates, and alcoholates can be used. 
     The obtained compound was purified by crystallization from hexane-ethylacetate mixture. Methods of crystallization are known to skilled persons in the art. The chemical structure of the compound was confirmed by elemental analysis, nuclear magnetic resonance (NMR), infrared (IR) analysis, ultraviolet (UV) analysis and mass-spectrometry. 
     The synthesized prodrug readily hydrolyses in vivo to indomethacin and menthol. The synthesized prodrug also demonstrates low toxicity and irritative properties and pronounced anti-inflammatory properties due to the fast release of indomethacin in the presence of esterases (see  FIG. 2  and  FIG. 3 ). 
     The inventors found that the presence of a menthol moiety in the prodrug molecule increases penetration of the substance through biological membranes, such as human skin, mucosal surfaces and the cornea, and significantly decreases eye irritation. 
     Several formulations of MEI were prepared, and tested for stability, toxicity, irritative properties and anti-inflammatory activity. Formulations that can be prepared include, but are not limited to, emulsions, microemulsions, liposomes, water based solutions, micellar preparations, suspensions and bioadhesive suspensions. In one embodiment, the end form of the product can include, but is not limited to, lotions, creams, ointments and gels. 
     In one embodiment, an effective or therapeutically effective amount of the composition is administered. An “effective amount” as used herein means an amount effective, at dosages and for periods of time necessary to achieve the desired results. Administration of a therapeutically effective amount of pharmaceutical compositions of the present invention is defined as an amount effective, at dosages and for periods of time necessary to achieve the desired therapeutic result. For example, an effective or therapeutically effective amount of a substance may vary according to factors such as the disease state, age, sex, and weight of the individual, and the ability of the substance to elicit a desired response in the individual. Dosage regimes may be adjusted to provide the optimum response. For example, several divided doses may be administered daily or the dose may be proportionally reduced as indicated by the exigencies of the therapeutic situation. In addition, an individual skilled in the art will appreciate that various excipients such as those set out in Remington:  The Science and Practice of Pharmacy,  20 th  edition, [Remington, 2000] may be added to the end topical composition. 
     Pharmaceutically acceptable carrier as used herein, such as a pharmaceutically acceptable ophthalmic carrier, includes excipients, diluents, adjuvants and vehicles and the like. It generally refers to components of the pharmaceutical composition other than the menthyl ester of indomethacin. In one embodiment, the components can aid in drug delivery, solubility or consistency of the drug for ophthalmic use. 
     The present invention is described in the following Examples, which are set forth to aid in the understanding of the invention, and should not be construed to limit in any way the scope of the invention. 
     EXAMPLES 
     Example 1 
     Menthyl Ester of Indomethacin (MEI)—Synthesis Description 
     18 g of indomethacin (50 mmol) and 8 g of natural menthol were dissolved in 200 ml dry toluene. 0.2 g of p-toluenesulfonic acid was added, and the mixture was boiled with a Dean-Stark trap until the required amount of the water was collected. After solvent evaporation, the residue was dissolved in ethylacetate-hexane mixture (1:4) and passed through a 2 cm layer of dry alumina (Beckman H activity level, 40-100 mesh). The solvent was evaporated, and the residue crystallized twice from ethylacetate-hexane 1:10. 
     MEI is a slightly yellow crystalline substance with a melting point of 86-90° C. It is insoluble in water, but freely soluble in alcohol, methylene chloride and chlorophorm, ethyl acetate, glycerides and other organic solvents. It is poorly soluble in propylene glycol and polyethylene glycol (PEG)-400. The NMR, mass-spectrometry and FT-IR-spectrum results were: 
     NMR 
     Found: C 70.47% H 6.98% N 2.71% Cl 7.36% 
     Theor. for C 29 H 34 NO 4 Cl: C 70.22% H 6.91% N 2.82% Cl 7.15% 
     Mass-spectra: (MW=496.05) 
     358 (Indomethacin), 496 (M + ), 497 (MH + ), 513 (M + +H 2 O), 514 (MH + +H 2 O) 
     FT-IR-spectrum (susp. in Nujol), showing the location of each peak: 3582.9 cm −1 , 2850.8 cm −1 , 2363.9 cm −1 , 1732.6 cm −1 , 1683.9 cm −1 , 1596.1 cm −1 , 1525.2 cm −1 , 1262.0 cm −1 , 1226.6 cm −1 , 1171.7 cm −1 , 1152.2 cm −1 , 1087.7 cm −1 , 1075.3 cm −1 , 1039.5 cm −1 , 1015.8 cm −1 , 985.2 cm −1 , 930.7 cm −1 , 904.7 cm −1 . 
     Example 2 
     Suspension of MEI (1 mg/ml and 2.5 mg/ml) 
     Crystallized MEI was dissolved in ethyl alcohol, containing non-ionic surfactant, to form 10% solution by weight (w/w). The prepared solution was diluted with purified water, and then buffer salts. Suspending polymer and preservative were then added and mixed until completely dissolved. The obtained suspensions (see Table 1) showed slow sedimentation and can be easily resuspended. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 COMPONENTS 
                 Suspension 2-1 
                 Suspension 2-2 
               
               
                   
               
             
            
               
                 MEI 
                 1.0% 
                 0.25% 
               
               
                 Ethyl alcohol USP 
                   1% 
                  2.5% 
               
               
                 TPGS (Tocophersolan USP) 
                 1.2% 
               
               
                 Tween-80 (Polysorbate 80 USP) 
                   
                 2.25% 
               
               
                 Sodium carboxymethylcellulose USP 
                   
                   2% 
               
               
                 Hydroxyethylcellulose USP 
                 1.5% 
               
            
           
           
               
               
            
               
                 Mono and disodium phosphate NF 
                 To pH 6.8 
               
            
           
           
               
               
               
            
               
                 Chlorobutanol USP 
                 0.2% 
                   
               
               
                 Benzalconium chloride USP 
                   
                 0.005%  
               
            
           
           
               
               
            
               
                 Water purified (USP) 
                 To 100% 
               
            
           
           
               
               
               
            
               
                 Particle size (microscopic estimation) 
                 2-5 mcm 
                 1-8 mcm 
               
               
                   
               
            
           
         
       
     
     Example 3 
     Micellar Preparation of MEI 
     Crystallized MEI was dissolved in melted Solutol HS-15 at 65-75° C. After a clear solution was obtained, hot water (75° C.) was added with intensive mixing, and the obtained dispersion was rapidly cooled to room temperature. After cooling, buffer components, glycerin (tonicity agent) and benzalconium chloride (preservative) were added. The prepared micellar formulation was sterilized by filtration through 0.1 mcm membrane filter. The formulation is as shown in Table 2. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 COMPONENTS 
                 % 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 MEI 
                 0.1 
               
               
                   
                 Solutol ® HS-15 
                 5.0 
               
               
                   
                 (Polyethoxylated 15-hydroxystearic acid, BASF) 
               
               
                   
                 Glycerin USP 
                 1.1 
               
               
                   
                 Monosodium phosphate dihydrate USP/NF 
                 0.40 
               
               
                   
                 Disodium phosphate dihydrate USP/NF 
                 0.72 
               
               
                   
                 Benzalconium chloride USP 
                 0.01 
               
               
                   
                 Water purified (USP) 
                 To 100% 
               
               
                   
                   
               
            
           
         
       
     
     Example 4 
     Water Based Solutions of MEI 
     0.1% clear solutions of MEI can be prepared in 33% w/w water solution of beta-hydroxypropyl-cyclodextrin (beta-HPCD, Encapsin®) or in 16% of 7-sulfobutylester of beta-cyclodextrin (Captisol®) by mixing for 12 hours, followed with 30 minutes sonication and filtration through 0.22 mcm microporous membrane, followed by pH and tonicity adjustment. 0.25% MEI solutions were prepared in 45% Encapsin® and 30% Captisol®, respectively. 
     Example 5 
     Emulsions Containing MEI 
     Crystalline MEI was dissolved in selected oil (containing surfactant) and heated to 45-55° C. The obtained solution was mixed with water phase, heated to 55° C. and the resultant solution, comprised of water, tonicity adjustment agent and preservatives, was emulsified using a high shear mixer of rotor-stator type (for example, the Omni GLH General Laboratory Homogenizer) at 6000-8000 rpm for 5 minutes. The emulsions prepared are shown in Table 3. 
     
       
         
           
               
               
             
               
                   
                 TABLE 3 
               
             
            
               
                   
                   
               
               
                   
                 Example # 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 5-1 
                 5-2 
                 5-3 
                 5-4 
                 5-5 
                 5-6 
                 5-7 
                 5-8 
                 5-9 
               
            
           
           
               
               
            
               
                 COMPONENTS 
                 % 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 MEI 
                 0.1 
                 0.25 
                 0.25 
                 0.25 
                 0.25 
                 0.25 
                 0.1 
                 0.25 
                 0.25 
               
               
                 Medium chain 
                 5 
                   
                   
                   
                   
                   
                   
                 2 
               
               
                 triglycerides 
               
               
                 USP/NF 
               
               
                 Tocopherol acetate 
                   
                   
                   
                 2.5 
                 2.5 
                   
                 1 
               
               
                 USP 
               
               
                 Acetylated 
                   
                   
                 5 
                   
                   
                   
                 2.5 
                 3 
                 2.5 
               
               
                 glycerides USP 
               
               
                 Tocopherol USP 
                   
                 2.5 
               
               
                 Castor oil 
                   
                   
                   
                   
                   
                 2.5 
               
               
                 Lecithin USP 
                   
                   
                   
                   
                   
                   
                 0.5 
                   
                 0.75 
               
               
                 Tyloxapol USP 
                   
                   
                   
                   
                 1.25 
               
               
                 Cremophor EL USP 
                 2 
                   
                 2 
                   
                   
                 2.5 
                   
                   
                 2.5 
               
               
                 Tocophersolan USP 
                   
                 1.5 
                   
                 1.25 
                   
                   
                 1 
               
               
                 Poloxamer 188 USP 
                   
                   
                   
                   
                   
                   
                   
                 2.5 
               
               
                 Polysorbate-80 USP 
                   
                   
                   
                   
                   
                   
                 1 
               
               
                 Sodium chloride 
                   
                   
                 0.85 
                   
                 0.85 
                   
                   
                 0.85 
               
               
                 USP 
               
               
                 Sodium edetate 
                   
                   
                   
                   
                   
                   
                 0.02 
                   
                 0.01 
               
               
                 USP 
               
               
                 Methylparaben USP 
                   
                   
                   
                 0.2 
                   
                   
                 0.2 
               
               
                 Benzalconium 
                 0.005 
                 0.01 
                   
                   
                 0.01 
                 0.01 
                   
                 0.01 
                 0.005 
               
               
                 chloride 
               
               
                 Alcohol USP 
                   
                   
                   
                   
                   
                   
                 0.5 
                   
                 0.75 
               
               
                 Glycerin USP 
                 2.2 
                 2.2 
                   
                 2.2 
                   
                 2.2 
                 1.5 
                   
                 1.0 
               
            
           
           
               
               
            
               
                 Water (purified) 
                 To 100% 
               
               
                 USP 
               
               
                   
               
            
           
         
       
     
     Example 6 
     Submicron Emulsion of MEI 
     0.75 g of MEI and 1.0 g of phospholipid (Lecithin USP) were added to 15 g of MCT oil, and the mixture was heated at 50° C.-65° C. to form a clear solution. The solution was mixed with 200 ml of a buffer solution (0.05M phosphate buffer, pH 6.8), and heated to 65° C. Then 4.5 g of glycerol (USP), 0.6 g of methyl paraben and 0.06 g of sodium edetate were added, the volume was adjusted to 300 ml with the said buffer solution, and then the mixture was treated with a rotor-stator type mixer (the Omni GLH) at 6000-8000 rpm for 5 minutes to form a coarse emulsion. This coarse emulsion was further treated using a high pressure homogenizer (Avestin C-5) at 15000-18000 psi (1000-1200 atm) for 5 cycles, and then passed through 0.45 mcm nylon membrane filter. A fine submicron emulsion was obtained. 
     Example 7 
     Bioadhesive Suspension of MEI 
     0.125 g of MEI was dissolved in 2 g of 50% (w/w) alcoholic solution of lecithin USP (Phospholipon S-80), containing 10% of Tocophersolan USP. The prepared mixture was diluted with 42 ml of hot (60° C.) water phase, comprising 1.5% Glycerin USP, 0.01% Sodium Edetate USP and 0.2% of Chlorobutanol USP. The obtained colloidal suspension was immediately mixed with 5 ml of 2% solution of bioadhesive polymer (Hydroxypropyl methylcellulose K4M, Chitosan Lactate or Sodium Hyaluronate) and filtered through 0.45 mcm nylon filter to remove large particles. 
     Example 8 
     Bioadhesive Emulsion of MEI 
     A bioadhesive emulsion of MEI was prepared dissolving sodium hyaluronate (0.4%) in a prepared emulsion (such as the emulsion prepared in Example 5-4). After complete dissolution of the polymer, the bioadhesive emulsion was filtered through 5 mcm nylon membrane filter and autoclaved for 15 minutes at 121° C. 
     Example 9 
     Poloxamer Gel of MEI 
     0.05 g of MEI was dissolved in 5 ml of PEG-400 USP at 60° C. In a separate vessel solution of 7.5 g of Poloxamer 188 USP and 5 g of Poloxamer 407 in 45 ml of cold (5-10° C.) purified water was prepared. Both solutions were combined at room temperature, sonicated for 30 minutes using a sonication bath, cooled and filtrated in cold state (e.g. at 5-10° C.) through 0.45 mcm nylon membrane filter. 
     Example 10 
     Comparison of Ocular Irritation Levels 
     The ocular irritation of MEI in an ophthalmic formulation as compared with an indomethacin-containing ophthalmic preparation has been tested in 3 healthy volunteers. One drop (40-50 mcl) of the tested formulations (0.25% of MEI (as per Example 5-9), 0.1% Indocollyre®, and sterile saline as the control) was placed onto the eye of each volunteer using an appropriate dropper. The interval between sample applications was at least 24 hours 
     The comparative irritation for MEI, indomethacin and other NSAIDs (Indocollyre®) in ophthalmic formulations is set out in Table 4 (volunteers data, n=3): 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                   
                   
                 MEI 0.25% 
               
               
                   
                 Control (Saline) 
                 Indocollyre ® 0.1% 
                 (Example 5-9) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Subj. 1 
                 1 
                 7 
                 2 
               
               
                 Subj. 2 
                 0 
                 6 
                 1 
               
               
                 Subj. 3 
                 1 
                 7 
                 1 
               
               
                 Average score 
                 0.67 
                 6.67 
                 1.33 
               
               
                   
               
            
           
         
       
     
     The irritation scale in the above table ranges from 0-10, with 0 corresponding to no burning or itching, and 10 corresponding to extremely severe burning or itching. Clearly, the ophthalmic formulation comprising MEI showed significantly lower irritation than indomethacin in solution. 
     Example 11 
     Pharmacokinetics of MEI in Rats 
     As presented in  FIG. 2 , MEI [20 mg/kg, submicron emulsion and Example 6] injected intraperitoneally into the body of Wistar rats rapidly metabolizes and releases indomethacin for a prolonged period, while the level of the parent substance (i.e. MEI itself), decreases rapidly. 
     Example 12 
     Comparative Anti-Inflammatory Activity of Indomethacin and MEI in a Carrageenan Model 
       FIG. 3  represents the anti-inflammatory activity of MEI in a carrageenan model. Inflammation in rats (n=4) was caused by injection of 100 microliters of sterile 1% carrageenan solution into a hind paw, originating local edema development with maximum development at 3-4 hours after administration. The contaralateral paw was injected with 100 microliters of saline and used as control. Paw volumes were measured by plethysmometry, (Ugo Basil Plethysmometer, Italy) and the calculated difference in paw volumes indicated the severity of inflammation. 
     Indomethacin released from intraperitoneally administrated MEI provides a high level of anti-inflammatory activity, and such activity correlates with the dose of administrated substance. 
     Example 13 
     Comparative Irritability of Indomethacin and MEI in Eyes 
     Two healthy volunteers instilled into 30 microliters of 0.1% Indomethacin ophthalmic solution (Indocid® ophthalmic, Merck) into their eye. The next day, 30 microliters of 0.25% MEI in emulsion (Example 5-4) was applied. Sterile saline (30 microliters) was used as a reference before the experiment. The observed results are represented below in arbitrary units. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 5 
               
               
                   
                   
               
               
                   
                   
                 Indomethacin 
                 MEI 
               
               
                   
                 Saline 
                 Indocid ® 
                 (Example 5-4) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Mean Irritation Score 
                 0.5 
                 3.5 
                 1.0 
               
               
                 (0 = no irritation, 
               
               
                 4 = severe irritation) 
               
               
                   
               
            
           
         
       
     
     While the present invention has been described with reference to what is presently considered to be a preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment. To the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
     All publications, patents, and patent applications are herein incorporated by reference in their entireties, to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference in its entirety. 
     REFERENCES 
     US Patents 
     
         
         1. U.S. Pat. No. 6,306,890 Kalgutkar, Amit S.; Marnett, Lawrence J. Esters derived from indolealkanols and novel amides derived from indolealkylamides that are selective COX-2 inhibitors 
         2. U.S. Pat. No. 6,762,182 Kalgutkar, Amit S.; Marnett, Lawrence J. Converting COX inhibition compounds that are not COX-2 selective inhibitors to derivatives that are COX-2 selective inhibitors 
         3. U.S. Pat. No. 5,496,811 Aviv, H.; Friedman, D.; Bar-Ilan, A.; Vered, M. Submicron emulsions as ocular drug delivery vehicles 
         4. U.S. Pat. No. 5,364,632 Benita, S.; Levy, M. Medicinal emulsions 
         5. U.S. Pat. No. 5,171,566 Mizushima, Y., et al. Flurbiprofen derivative ophthalmic preparation 
         6. U.S. Pat. No. 4,613,505 Mizushima, Y., et al. Ester of flurbiprofen and emulsion containing the same 
         7. U.S. Pat. No. 5,998,465 Hellberg, M., et al. Esters of non-steroidal anti-flammatory carboxylic acids 
       
    
     Articles 
     
         
         1. Salva P, Costa J, Andreu D, Notivol R, Martinez M. TOLERABILITY AND SAFETY OF 0.1% DICLOFENAC PLUS 0.3% TOBRAMYCIN FIXED-DOSE OPHTHALMIC SOLUTION: A RANDOMIZED, COMPARATIVE, CONTROLLED STUDY IN HEALTHY VOLUNTEERS. Methods Find Exp Clin Pharmacol. 1999 April; 21(3):203-8. 
         2. Scuderi B, Driussi G B, Chizzolini M, Salvetat M L, Beltrame G. EFFECTIVENESS AND TOLERANCE OF PIROXICAM 0.5% AND DICLOFENAC SODIUM 0.1% IN CONTROLLING INFLAMMATION AFTER CATARACT SURGERY. Eur J Ophthalmol. 2003 July; 13(6):536-40. 
         3. Mccarey B., Napalkov J., Pippen P., Koester J. and Al Reavers T. CORNEAL WOUND HEALING STRENGTH WITH TOPICAL ANTIINFLAMMATORY DRUGS. Cornea, 1995, 14: 290-294. 
         4. Stroobants A., Fabre K. Maudgal P. EFFECT OF NON-STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAID) ON THE RABBIT CORNEAL EPITHELIUM STUDIED BY SCANNING ELECTRON MICROSCOPY Bull. Soc. Beige Ophtalmol., 276, 73-81, 2000. 
         5. Diestelhorst M, Schmidl B, Konen W, Mester U, Raj P S. EFFICACY AND TOLERANCE OF DICLOFENAC SODIUM 0.1%, FLURBIPROFEN 0.03%, AND INDOMETHACIN 1.0% IN CONTROLLING POSTOPERATIVE INFLAMMATION. J Cataract Refract Surg. 1996; 22 Suppl 1:788-93. 
         6. Aggarwal D, Kaur I P. IMPROVED PHARMACODYNAMICS OF TIMOLOL MALEATE FROM A MUCOADHESIVE NIOSOMAL OPHTHALMIC DRUG DELIVERY SYSTEM. Int J Pharm. 2005 Feb. 16; 290(1-2):155-9. 
         7. Mainardes R M, Urban M C, Cinto P O, Khalil N M, Chaud M V, Evangelista R C, Gremiao M P. COLLOIDAL CARRIERS FOR OPHTHALMIC DRUG DELIVERY. Curr Drug Targets. 2005 May; 6(3):363-71. 
         8. De T K, Bergey E J, Chung S J, Rodman D J, Bharali D J, Prasad P N. POLYCARBOXYLIC ACID NANOPARTICLES FOR OPHTHALMIC DRUG DELIVERY: AN EX VIVO EVALUATION WITH HUMAN CORNEA. J. Microencapsul. 2004 December; 21(8):841-55. 
         9. Calvo P, Alonso M J, Vila-Jato J L, Robinson J R. IMPROVED OCULAR BIOAVAILABILITY OF INDOMETHACIN BY NOVEL OCULAR DRUG CARRIERS. J Pharm Pharmacol. 1996 November; 48(11):1147-52. 
         10. Remington: THE SCIENCE AND PRACTICE OF PHARMACY, 20 th  edition, Lippincott, Williams and Wilkins, Philadelphia, 2000.