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NOVEL OCULAR DOSAGE FORM IN THE TREATMENT OF GLAUCOMA
Abstract
Glaucoma is a group of disease of the eye characterized by damage to the ganglion cells and the optic nerve. If left untreated, these effects may lead to various degrees of loss of vision and blindness. Increased intraocular pressure (IOP) remains the most important risk factor for the development of glaucoma. A major problem in ocular therapeutics is the attainment of an optimal drug concentration at the site of action. To achieve effective ophthalmic therapy, an adequate amount of active ingredient must be delivered and maintained within the eye. The most frequently used dosage forms i.e., eye solution, eye ointments, eye gels and eye suspensions are compromised in their effectiveness by several limitations leading to poor ocular bioavailability. Occusert are thin discs or small cylinders made with appropriate polymeric material and fitting into the lower or upper conjunctival sac. Their long persistence in preocular area can result in greater drug availability with respect to liquid and semisolid formulation. Thus occusert can be used for the controlled delivery of drugs used in the treatment of glaucoma.
... Pharmacosomes remove various shortcomings of vesicular drug delivery systems, such as low drug entrapment, leakage from carrier and short shelf life [56]. Imam et al., (2009) reviewed various types of ocular dosage forms for the treatment of glaucoma [57]. Semalty et al., (2009) prepared pharmacosomes of diclofenac using phosphatidylcholine (80%) and observed improvement in hydrophilicity of the prepared vesicles that displayed lower toxicity and better bioavailability [58]. ...
... Pharmacosomes remove various shortcomings of vesicular drug delivery systems, such as low drug entrapment, leakage from carrier and short shelf life [56]. Imam et al., (2009) reviewed various types of ocular dosage forms for the treatment of glaucoma [57]. Semalty et al., (2009) prepared pharmacosomes of diclofenac using phosphatidylcholine (80%) and observed improvement in hydrophilicity of the prepared vesicles that displayed lower toxicity and better bioavailability [58]. ...
Oral drug delivery has always been considered the preferred route of drug administration. Nano-formulations are now constantly being researched for better absorption, higher bioavailability and greater therapeutic efficacy. Lipid based nanoformulations have found much favour with the formulation scientist due to their relatively higher safety profile and enhancement of bioavailability.These delivery systems are also able to protect the bioactives or drugs from the vagaries of the gastrointestinal tract. They also aid in the absorption of hydrophobic drugs which are entrapped in lipid matrices. Lipid excipients have been known to reduce efflux which is P-glycoprotein mediated and also to increase the bioavailability of bioactives which are given through the oral route.
In the last 20 years, about a thousand articles and reviews about oral lipid carriers have been reported. Many dosage forms have been made by modifying liposome, sometimes to overcome a disadvantage and at other times to modify the dosage form in such a manner so as to suit the requirement of the drug molecules. Various other lipidic drug delivery systems also exist which are not vesicular but being made of lipids, are equally useful for delivering lipophilic drugs. Although a Lipid Formulation Classification System exists, but there is no exhaustive review which discusses the entire lipid based, oral nanoformulations. The present review envisages discussing the various types of oral, lipid, nanosized, delivery systems available, so that an insight is gained into all these carriers, and the formulation scientist can make a judicious decision regarding choice of a lipid based carrier.
... • Increased ocular contact time and thus improved drug bioavailability [7]. • Increased ocular permeation with respect to standard formulation and thus providing prolong drug activity and hence increased ocular bioavailability of drug [8]. ...
The main aim of the present study is to formulate an effective ocular insert of Clotrimazole (an antifungal drug), which can produce
a better ocular therapy against ocular fungal infections by increased bioavailability through increased drug-eye contact time
and controlling the trans-corneal permeation of drug. We intend to optimize the formulation to show constant release of drug for
maintenance of dose over a prolonged period of time. For the purpose we prepared ocular insert formulations of Clotrimazole. Various
formulations were prepared by use of different polymers, HPMC, EC and combination of both in different proportions 2%, 3%
and 4%. The prepared formulations were evaluated for various physical and analytical parameter related to appearance, durability,
uniformity of drug contents, in-vitro and in-vivo release of drug and for stability. Ocuserts of Clotrimazole were prepared by solvent
casting method followed by preparing the drug reservoir film and rate controlling membrane separately. Evaluation of ocular inserts
for weight and thickness variation were carried out and analyzed by ANOVA. The % drug release from the selected formulation containing
HPMC, were found to be 91.78 ± 2.436 at the end of 360 minutes. From current study we can conclude that by using different
polymer in rate controlling membrane of an ocusert, release rate of drug from ocusert can be controlled or altered.
Keywords: Ocusert; Clotrimazole; HPMC; EC; ANOVA
... Due to the continuous secretion of aqueous humor, pressure in the posterior chamber forces the iris to bulge forward. This can progress towards completing the blockage of drainage (Imam et al., 2009). ...
Context: Glaucoma is a disease of the eyes characterized by an increase in the intraocular pressure. Timolol maleate is commonly used as eye drops for chronic glaucoma treatment.
Aims: To formulate an ocusert (novel ophthalmic drug delivery systems) in order to overcome disadvantages of eye drops such as patient’s noncompliance and drainage of the administered solution. Also, to improve treatment outcomes by keeping sustained release of constant amount of timolol maleate and to avoid repeated administration of conventional eye drops.
Methods: Timolol maleate ocuserts were formulated using cross-linked gelatin polymer which was prepared using N-(3-dimethylaminopropyl)-N-ethylcarbodiimide (EDC) and N-hydroxysuccinamide (NHS). Different ocusert formulas were prepared (M1-M17) by varying concentrations of EDC, different temperatures and time for the cross linking as per central composite design. Physicochemical characteristics of drug loaded ocuserts were investigated.
Results: Selected formula (M8) exhibited an excellent in vitro drug release results which was extensively evaluated. Fourier transform infrared spectral scan indicates no incompatibility exists between the drug and the polymer used. M8 formula was evaluated in vivo by assessing the eye irritancy, drug release and therapeutic effect when placed in the cul-de-sac of rabbit’s eyes and was compared with conventional eye drops therapy.
Conclusions: There was a correlation between in vivo and in vitro release of timolol maleate which is associated with a decrease of glaucoma induced by dexamethasone eye drops in experimental rabbits. The data established the potential of ocusert to improve the therapeutic delivery of timolol maleate and offers a promising option in glaucoma treatment.
... To be effectively absorbed, the drug must have differential solubility, i.e., the ionized and non-ionized form. [12] Different anatomical barriers to restrict ocular dosage form ...
Treatment with traditional ocular dose structure has a wide range of issues such as obscured vision, loss of medication by seepage, irritation, non-maintain activity, persistent noncompliance, nature of medication, and so on furthermore diminishes the visual bioavailability of medication. To minimize these issues, novel ocular dose structures are utilized for some visual diseases. Distinctive novel ocular measurement frames like controlled dose shape that is inserts, liposomes, nanoparticles, visual supplements, contact lenses, iontophoresis, and so on, have managed the influx of medication particles by moderate degradation of the polymer. These measurement frames build the contact time of medication particles with ocular tissues, which infiltrates the medication particles into more profound tissues of the eye furthermore expands the visual bioavailability of medication. Novel medication conveyance through the ophthalmic course has real change for future perspectives.
... The most important and the only proven modifiable risk factor for glaucoma is increased IOP. [33] The role of IOP reduction in preventing optic nerve damage and visual loss has been upheld in numerous randomized prospective trials. Medical therapy is the standard of care in POAG and also the mainstay of initial and long-term IOP reduction in other types of glaucoma. ...
Background: Glaucoma is a chronic, progressive optic neuropathy which leads to optic nerve damage and loss of visual function. Elevated intraocular pressure (IOP) is the most important and only modifiable risk factor. Hence, the goal of glaucoma therapy is to lower IOP, and ocular hypotensive agents have the potential to prevent optic nerve damage and preserve vision. Aims and Objectives: Aims and objectives of the study are to compare the efficacy and safety of timolol 0.5% versus latanoprost 0.005% in the treatment of primary open-angle glaucoma (POAG). Materials and Methods: A total of 60 newly diagnosed patients of POAG who fulfilled the inclusion/exclusion criteria were enrolled and randomized into two groups of 30 each to receive timolol 0.5% twice daily and latanoprost 0.005% once daily in the evening. IOP was recorded at baseline and each follow-up visit. The patients were followed every 4 weeks for 12 weeks. Adverse effects, if any, were also recorded at each visit. Results: At 12 weeks both timolol and latanoprost effectively reduced IOP, but the reduction was significantly greater (P < 0.0001) with latanoprost (7.97 ± 1.27 mmHg, 31.25%) compared with timolol (6.77 ± 1.48 mmHg, 25.9%). More number of eyes (χ² = 4.6, df = 1, P = 0.032) treated with latanoprost (46, 76.6%) achieved a specific target IOP as compared to those treated with timolol (35, 58.3%). Both the study medications were well tolerated. Conclusion: Latanoprost was found to be more potent and efficacious in reducing IOP with good tolerability in patients with POAG.
... Niosomes: These are microscopic lamellar structures formed from a non-ionic surfactant and a lipid, which are capable of entrapping both hydrophilic and lipophilic drug. These also, like other novel dosage forms provide prolonged residence times, enhanced therapeutic efficacy and greater drug absorption and permeation(Imam et al., 2009). Niosomal formulation of timolol maleate has shown greater efficacy in lowering the IOP in glaucoma and extended drug release over time in comparison to its gel formulation(Aggarwal, 2005). ...
Open angle glaucoma is an ocular neurodegenerative disease that is characterized by elevated intraocular pressure (IOP) and neurodegeneration of retina ganglion cell (RGC) and optic nerve head (ONH), leading to blindness. Although the current therapies are aimed at decreasing IOP, a small proportion of open angle glaucoma patients exhibit normal IOP. Therefore, there is a need for therapeutic approaches that simultaneously reduce the elevated IOP and provide RGC protection. Hydrogen sulfide (H2S) reportedly displays both of these activities in a concentration range of 10-200 μM. It can be toxic at a higher concentration and its donors are unstable in water. Thus, a search for a hydrophobic, sustained release delivery system for H2S donors is warranted in order to harness its therapeutic potential. This study investigated the preparation and characterization of a non-aqueous in situ gelling sustained release delivery system for H2S donors. A HPLC method was developed for quantification of H2S in aqueous medium. The accuracy (% error < 10%) and precision (% RSD < 5%) of the methods were in compliance with USP guidelines for validation of an assay method. The delivery system was prepared by dissolving 10% w/v poly (lactic-co-glycolic acid) in benzyl benzoate and benzyl alcohol (3:7). The formulation was prepared by dispersing model H2S donor, GYY 4137, into
iv
polymer solution. The formulation rapidly formed an in situ gel upon injecting in simulated tear fluid. Compared to aqueous GYY 4137 solution, the formulation sustained and extended the H2S release significantly (p < 0.05). Rheological study of the delivery system indicated a shear-thinning plastic flow with 43.89 ± 3.21 cP viscosity and 1.12 ± 0.15 Pa yield value which corroborates its easy syringeability and injectability. Karl Fisher titrimetry indicated presence of 0.66 ± 0.10 % weight of inherent water which does not hydrolyze GYY 4137. The NMR spectroscopic study indicated presence of 4-methoxyphenylphosphonic acid (a GYY 4137 degradation product) in STF confirming the mechanism of H2S release. Benzyl benzoate and benzyl alcohol solvent blend exhibited toxicity in Y79 retinoblastoma cells which should be substituted with less toxic solvent in a future extension of this study.
... These terms are based upon the mechanism of obstruction of outflow of aqueous humor and help clinicians for developing treatment strategies. A third type is congenital glaucoma, which results from developmental ocular 1 abnormalities and occurs in less than 2% of patients . Among asians, the incidence of closed angle glaucoma is almost twice as high as that for caucasians. ...
The aim of present study was to characterize best optimized Levobunolol HCl occusert formulations with special reference to glaucoma treatment, biologically. Levobunolol HCl occuserts were prepared using hydroxypropyl methylcellulose (HPMC, 3% & 4%), poly vinyl pyrrolidone (PVP, 1%), methyl cellulose (MC, 1% & 2%) as polymers by solvent casting technique with objectives of increasing contact time, achieving controlled release, reduction in frequency of administration and greater therapeutic efficacy. Based on their physiochemical and in-vitro drug release characterization, formulations (F 2 & F 1)containing 4% and 3% HPMC were selected as best optimized formulations. Further, these formulations were subjected to biological characterization such as microbial sterility testing, Modified Draize eye irritation and in-vivo drug release studies for their efficacy, reliability and clinical safety. Finally, accelerated stability testing (aging study) was also carried out. Results of these studies revealed that, occusert formulations (F 2 & F 1) passed the test for sterility, there was no irritation to the sensitive ocular tissues and in-vivo study had released drug contents, 77.14% and 69.83% (F 2 & F 1) respectively over an extended period of 12 hr. Finally, the ocular inserts were found stable and there was no effect on the drug content for a period of 2 months. It was found that, best optimized polymeric occuserts have appreciable strength biologically.
... These terms are based upon the mechanism of obstruction of outflow of aqueous humor and help clinicians for developing treatment strategies. A third type is congenital glaucoma, which results from developmental ocular 1 abnormalities and occurs in less than 2% of patients . Among asians, the incidence of closed angle glaucoma is almost twice as high as that for caucasians. ...
The aim of present study was to design and in-vitro characterization of Levobunolol HCI occuserts with special reference to glaucoma treatment. Levobunolol HCI ophthalmic solution has been shown to be effective in IOP and may be used in patients with chronic open-angle glaucoma or ocular hypertension. The Levobunolol HCI occuserts were prepared using hydroxypropyl methylcellulose (HPMC, 3 & 4%), poly vinyl pyrrolidone (PVP, 1%), methyl cellulose (MC, 1 & 2%) as polymers by solvent casting technique with objectives of increasing contact time, achieving controlled release, reduction in frequency of administration and greater therapeutic efficacy. The prepared occuserts were then evaluated for there physical appearance and surface texture, weight variation, uniformity of thickness, tensile strength and % elongation at break, % moisture uptake, % moisture loss, folding endurance, drug content and in-vitro drug release. It is evident from these studies that, formed polymeric occuserts have appreciable strength and safety. Physiochemical characterization and in-vitro drug release studies reveals that, the prepared occusert formulations (F 2 F 1) containing 4% and 3% HPMC had released theirdrug content, 83% and 81% respectively over an extended period of 12 hr. Hence, these formulations were selected as best optimized formulations.
This research paper describes the objective of the present study to formulate ophthalmic mucoadhesive in situ gelling system of Dorzolamide Hydrochloride using two different polymers namely Poly Acrylic Acid and Xanthan Gum, individually and in combinations.Cellulose (HPMC) was used as viscosity enhancing agent. The developed formulations were subjected to several evaluation parameters including physico-chemical properties, compatibility, in-vitro drug release, microbiological, ex-vivo and stability testing and compared with marketed formulation wherever possible. All formulations were found to be milky with pH between 6.0 to 6.5 for sols and nearly neutral for gels. All formulations showed instantaneous gelling with translucent gel matrix which retained its integrity for extended period of time. The viscosity of best formulation (F4) was found to be 20 cps. The drug was compatible with both the polymers and the viscoliser in both solid as well as liquid states. Invitro drug release studies showed that all the formulations released drug over a period of 12 hours with formulation F4 (0.2% w/v Xanthan Gum) showing the highest drug release of 90.84% of Dorzolamide Hydrochloride. All the formulations showed zero order drug release with the release mechanism being diffusion along with erosion of gel matrix for all formulations. Further the drug release from all the formulation was observed to be nonfickian. The best batch showed ex-vivo drug release through goat's cornea for 9 hours with the release kinetics being similar to those seen with in-vitro drug release. All the formulations were found to be sterile.
The reverse micelle is one of many models thought to have properties more nearly resembling the biological cellular environment, than does the traditional dilute-solution biochemical reaction system. The reverse micellar ocular system was prepared using cetyltriammonium bromide, span 60 alone and in combinations in organic solvent of isopropylpal mitate:isopropylmyristate (50:50). The designed systems were characterized for drug content and the process variables that effect the percent drug payload and release profiles of drug. The effect of hydration, temperature and ionic strength on drug pay load on reverse micellar systems had been considered for the present study. Systems were evaluated for in vitro performance. The drug release was recorded to follow approximate first order release kinetics. On the basis of in vitro characterization the selected systems were evaluated for in vivo activity. It was observed that the micellar systems exhibited prolonged and controlled biological response of timolol maleate.
The poor uptake of many ophthalmic drugs is mainly due to the rapid elimination process by tear turnover. A prolonged precorneal residence time would result in higher absorption and, for some drugs, a prolonged duration of their therapeutic effect. It is known that gels are retained better in the eye than ordinary solutions but relatively little is known about the importance of the rheological properties of gels for their retention. In this study the ocular residence time of carbomer gels have been monitored in humans and the gels were also rheologically characterised. The contact time of Carbopol 974P and Carbopol 1342NF was concentration dependent and was approximately 2–2.5 h for a 2% gel. There was a good correlation of the human contact time and the elastic properties of the gels. The miotic response from gels with pilocarpine nitrate was monitored in rabbits and the area under the curves (AUCs') were calculated. The relative AUCs were 1.5–2.1 for the gel preparations relative to a solution. No concentration dependence was seen and there was no significant difference in AUC between the different carbomers. The ocular contact time of the gels were much less in rabbits than those obtained in humans.
The poor bioavailability and therapeutic response exhibited by conventional ophthalmic solutions due to rapid pre-corneal elimination of the drug may be overcome by the use of in situ gel-forming systems that are instilled as drops into the eye and then undergo a sol-gel transition in the cul-de-sac. The present work describes the formulation and evaluation of an ophthalmic delivery system of an antibacterial agent, gatifloxacin, based on the concept of ion-activated in situ gelation. Alginate (Kelton) was used as the gelling agent in combination with HPMC (Methocel E50Lv) which acted as a viscosity-enhancing agent. The rheological behaviors of all formulations were not affected by the incorporation of gatifloxacin. Both in vitro release studies and in vivo pre-corneal retention studies indicated that the alginate/HPMC solution retained the drug better than the alginate or HPMC E50Lv solutions alone. These results demonstrate that the alginate/HPMC mixture can be used as an in situ gelling vehicle to enhance ocular bioavailability and patient compliance.
To study the in vitro and in vivo release pattern of a drug from different types of ophthalmic formulations, three different formulations were prepared, viz., conventional solution, aqueous polymeric gel and hydrophobic ointment. Ciprofloxacin was used as the model drug. In the vitro studies, the gel prolonged the release for about 30 mins., whereas the ointment did not release any drug at all. In the in vivo studies, carried out in healthy rabbits, the highest drug levels were obtained with the gel, followed by the conventional solution and lowest with the ointment.
Poor bioavailability of ophthalmic solutions caused by dilution and drainage from the eye can be overcome by using in-situ-forming ophthalmic drug delivery systems prepared from polymers that exhibit reversible liquid-gel phase transition. In the present paper, we demonstrate that an aqueous solution of sodium alginate can gel in the eye, without the addition of external calcium ions or other bivalent/polyvalent cations. The extent of alginate gelation and consequently the release of pilocarpine, depended on the percent guluronic acid (G) residues in the polymer backbone. Alginates with G contents of more than 65%, such as Manugel DMB, instantaneously formed gels upon their addition to simulated lacrimal fluid, while those having low G contents, such as Kelton LV, formed weak gels at a relatively slow rate. In vitro studies indicated that pilocarpine is released slowly from alginate gels, over a period of 24 h, and the release occurs mostly via diffusion from the gels. Dissolution of the hydrogels in the releasing media was negligible for the first 12 h of incubation at 37°C. Intraocular pressure (IOP) measurements of rabbit eyes treated with 2% (w/v) pilocarpine nitrate in solution, or in the in-situ gel forming formulation composed of the high G content DMB alginate, indicated that DMB significantly extended the duration of the pressure reducing effect of pilocarpine, to 10 h, as compared to the 3 h when pilocarpine nitrate was delivered as a solution. In contrast, there was no apparent difference in the duration and extent of IOP decrease between rabbits treated with pilocarpine in solution or in the Kelton LV alginate eye drop formulations. The overall results of this study indicate that the in situ-gelling alginate system, based on polymers with high G contents, is an excellent drug carrier for the prolonged delivery of pilocarpine.
The possibility of using liposomes as an ophthalmic drug delivery carrier for the lipophilic drug, pilocarpine HCl, was investigated on the eyes of normal and glaucomatous pigmented rabbits. The intraocular pressure (IOP) of rabbits was measured, using a Shi∅tz tonometer, as a function of time after topical administration with free drug, neutral and negatively charged multilamellar vesicles (MLVs) encapsulating pilocarpine HCl. The results showed that administration with neutral MLVs displayed the most prolonged effect with respect to negatively charged MLVs and free drug. The efficiency of MLVs encapsulating pilocarpine HCl, measured using spectrophotometric technique, was found to be 96% in our modified preparations. The storage stability of MLVs encapsulating pilocarpine HCl was investigated by measuring phase transition and size distribution using light scattering technique. The results show that liposomes encapsulating pilocarpine HCl have kept their integrity and physicochemical properties for at least 15 months, which makes them suitable for commercial use.
The orally administered acetazolamide has a limited use in glaucoma due to the systemic side effects associated with its use. It has been reported to show little effect on the intraocular pressure (IOP) of human and rabbit eyes upon topical application, probably owing to its poor bioavailability and instability at pH >5.0. In order to enhance the bioavailability of the drug, contact time between the drug molecules and the ocular surface was increased using high viscosity, water soluble polymers (PVA, HPMC), and by incorporating acetazolamide into an in situ-forming ophthalmic drug delivery system. Moreover, a penetration enhancer (EDTA) was also used in these formulations to increase the extent of absorption of the drug. Acetazolamide at a concentration of 10% was used and the formulations (eyedrop suspensions) were evaluated for their in vitro release pattern. The effect of these formulations on the IOP in normotensive conscious rabbits was also investigated. These formulations were found to be therapeutically effective with a peak effect at 2 h. A fall in IOP of up to 46.4% was observed with repeated administration of one of the formulation containing PVA, EDTA and Tween 80 (MK-5). Results indicated that a topical effect of acetazolamide can be observed if the formulation, (a) contains a suitable polymer-to increase the residence time; (b) a penetration enhancer-as acetazolamide has a low permeability coefficient i.e. 4. 1x10(-6) cm/s [Duffel, M.W., Ing. I.S., Segarra, T.M., Dixson, J.A., Barfknecht, C.F., Schoenwald, R.D., 1986. J. Med. Chem. 29, 1488-1494]; and (c) pH of the formulation is maintained at the point of maximum stability (pH< or =5.0).
Polymeric micelles made of copolymer of N-isopropylacrylamide (NIPAAM), vinyl pyrrolidone (VP) and acrylic acid (AA) having cross-linkage with N,N'-methylene bis-acrylamide (MBA) were used as host carrier in which up to 30%w/w ketorolac (free acid) was entrapped to make the formulation. The lyophilised powder was used for physical characterisation. The drug entrapment was found to be about 80% and the formulation was stable for 8-10 days at room temperature. The smaller the amount of ketorolac dissolved into the micelles, the longer was the formulation shelf life. The size of the particles as measured by dynamic light scattering was found to be around 35 nm diameter at 25 degrees C. TEM picture showed spherical particles. The structure of the polymer and its morphology were characterised by FTIR, NMR and XRD measurements. IR data indicated weak interaction between polymer and ketorolac in the encapsulated system. NMR spectra indicated rigid polymer backbone with intermittent iso-propyl group in the chain. XRD spectra showed significant loss of crystallinity of the drug while being entrapped in the polymeric micelles. The release of drug in aqueous buffer (pH 7.2) from the polymeric micelles at 25 degrees C were 20 and 60% after 2 and 8 h respectively and is temperature and pH dependent. In vitro corneal permeation studies through excised rabbit cornea indicated two fold increase in ocular availability with no corneal damage compared to an aqueous suspension containing same amount of drug as in nanoparticles. The formulation showed significant inhibition of lid closure up to 3 h and PMN migration up to 5 h compared to the suspension containing non-entrapped drug, which did not show any significant effect.
The present study investigates the use of a polymer mixture containing Carbopol 974P and drum dried waxy maize starch to obtain prolonged drug release to the anterior eye segment. Two dosage forms with this composition are compared: a hydrated polymer dispersion and a minitablet. A model fluorescent tracer is used to study the ocular release and diffusion from the two dosage forms in humans. To evaluate the prolongation in the cornea/tearfilm compartment, the Apparent Fluorescein TurnOver (%/min) is calculated. The parameters Cmax, tmax, and C9h are used to characterize the pharmacokinetics of Na-fluorescein in the anterior chamber. Furthermore, the swelling behavior of the minitablet is evaluated macroscopically, while the degree of interaction with mucin is characterized by rheological measurements. Calculation of an acceptability score and a slug irritation potential is performed to evaluate user acceptability. In contrast to the hydrated dispersion, the minitablet significantly decreases the Apparent Fluorescein TurnOver (%/min) (P<0.05) and increases the apparent fluorescence in the anterior chamber 9 h after application of the preparation. Rheological data demonstrate the presence of elastic interactions between the polymer and mucin. The dry core of the minitablet becomes fully hydrated after approximately 2 h and is subsequently transformed into a highly concentrated gel. The acceptability of the minitablet is comparable to that of the polymer dispersion. Prolonging the release of Na-fluorescein to the anterior eye segment is only feasible with the dry preparation.
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