Release of Ciprofloxacin from Chondroitin 6-Sulfate-Graft-Poloxamer Hydrogel In Vitro for Ophthalmic Drug Delivery

The system was designed to use Poloxamer as a vehicle for ophthalmic drug delivery using in situ gel formation property. To enhance the wound healing and cell adhesion as well as transparency of Poloxamer hydrogel, chondroitin 6-sulfate (C6S) was introduced into Poloxamer. For this purpose, mono amine-terminated Poloxamer (MATP), which was end-capped with ethylene amine group only in one side of terminal hydroxyl groups of Poloxamer, was synthesized. Subsequently, C6S-graft-Poloxamer copolymer (C6S-g-Poloxamer) was prepared by reaction between the amine groups of MATP and carboxyl groups of C6S in the presence of 1-ethyl-3-(3-dimethylaminopropyl)-carboimide (EDC). The coupling of MATP with C6S was clarified by 1H-NMR and FT-IR spectroscopy. The gelation temperature of graft copolymers was determined by measuring the temperature at which immobility of the meniscus in each solution was first noted. Release behavior of ciprofloxacin from C6S-g-Poloxamer hydrogel in vitro was investigated as a function of C6S content in the graft copolymer by a spectrophotometric assay at 287 nm using an UV spectrophotometer. Differences in the adhesion and morphology of human lens cell between Poloxamer- and C6S-g-Poloxamer-coated surfaces were also investigated. The gelation temperatures of C6S-g-Poloxamer copolymers were lowered with increasing of the concentration of the copolymer and decreasing of C6S content. The release of ciprofloxacin from the graft copolymer was sustained compared with Poloxamer itself and decreased with increasing the content of C6S in the copolymer due to the in situ gel formation of the copolymer and viscous properties of C6S. Human lens cells (B3) adhered to C6S-g-Poloxamer-coated surface were observed as transformed shapes after 2 days. The bioadhesive and thermally gelling of these graft copolymers will be expected to be an excellent drug carrier for the prolonged delivery to surface of the eye.

[Ocular penetration and pharmacokinetics of topical voriconazole in rabbit eyes]

OBJECTIVE

To investigate the penetration of topical 1% voriconazole into the cornea and aqueous humor in New Zealand white rabbits.

METHODS

It was a experimental study. Forty-eight healthy rabbits were randomly divided into groups A (21 cases), B (21 cases) and C (6 cases). Blank samples from group C were used to determine the essential parameters for the validation of analytical procedures. A single 50 microl drop of 1% voriconazole was administered in group A (non-debrided cornea) and group B (debrided cornea). The aqueous humor and the cornea were obtained at 2, 5, 10, 15, 30, 60 and 90 min after application. All samples were analyzed by high-performance liquid chromatography (HPLC). The HPLC system consisted of Waters 1525 pump, Phenomenex Luna C18 (250.0 mm x 4.6 mm, 5.0 microm) column, Phenomenex C18 (4.0 mm x 3.0 mm, 5.0 microm) analytical steel column and a Waters Empower data workstation. The UV detector was set to 255.0 nm. Methanol-0.04 mol/L ammonium hydroxide (62:38, V/V) was used as mobile phase and the flow rate was 0.8 ml/min. External standard was used in this assay. The pharmacokinetic parameters were calculated with nonlinear least square method by the computer.

RESULTS

Calibration curves were linear over the range 0.1-15.0 mg/L. The concentration at 0.1 mg/L was the lowest quantified limit. The recovery of voriconazole from aqueous humor samples ranged from 91.06% to 94.80%, and ranged from 79.84% to 83.20% in the cornea samples. After single dose application, the drug concentration in aqueous humor peaked at 10 min in both group A [ (5.172 +/- 1.012) mg/L] and group B [(6.118 +/- 1.123) mg/L], and the parameters t(1/2 ke) in groups A and B were 6.859 min and 13.176 min, respectively. However, peak drug levels were achieved immediately at 2 min in the cornea [group A: (9.958 +/- 3.481) microg/g and group B: (158.476 +/- 10.462) microg/g]. The parameter t(1/2 beta) in nondebrided cornea was 94.938 min and 46.367 min in debrided corneas.

CONCLUSIONS

Topical voriconazole exhibits excellent penetration into the cornea, and effective high drug levels are achieved in both the cornea and aqueous humor after single dose application. It can be a prominent agent for the treatment of fungal keratitis in the future.

A Novel In Vivo Rabbit Model that Mimics Human Dosing to Determine the Distribution of Antibiotics in Ocular Tissues

PURPOSE

The aim of this study was to establish a novel method to predict the human ocular penetration and distribution of topical antibiotics by using a controlled rabbit model that mimics the human eye with manual blinking and tear flow.

METHODS

After anesthetizing the rabbits, a single dose of commercial antibiotic formulations was given with precision directly onto the cornea. This was followed by a 30-min controlled period applying manual blinking (4 blinks/min) and a supplementary tear flow (2 microL/min) that mimics the human eye. Tear samples were collected every 5 min and after euthanasia, conjunctival, aqueous humor, iris-ciliary body, and scleral samples were collected. The corneas were mounted in perfusion chambers to determine the level and continuing rate of release of the antibiotics, the levels of which were all determined using high-performance liquid chromatography analysis.

RESULTS

U.S. formulations achieved conjunctival and corneal levels (μg/g) as follows: moxifloxacin, 6.6 +/- 0.3 and 50 +/- 5; tobramycin, 3.1 +/- 1.4 and 20 +/- 5; gentamicin, <2 and <2; levofloxacin, 1.5 +/- 0.3 and 19 +/- 2; gatifloxacin, 0.9 +/- 0.1 and 11 +/- 1; and trimethoprim, <0.1 and 2 +/- 1. Japan formulations achieved conjunctival and corneal levels as follows: levofloxacin 2.1 +/- 0.8 and 12 +/- 2; gatifloxacin, 2.2 +/- 0.9 and 7 +/- 1; ofloxacin, 1.6 +/- 0.5 and 7 +/- 1; and tosufloxacin, 0.7 +/- 0.1 and 1.5 +/- 0.3 (mean +/- standard error, n = 4).

CONCLUSIONS

Moxifloxacin achieved the highest levels of antibiotic in ocular tissues. In the conjunctiva and cornea, the moxifloxacin level was 3-30 times the level of other fluoroquinolones, at least twice the level of the aminoglycosides, and 25 times the level of the antibacterial trimethoprim.

Poly(N-isopropylacrylamide)–chitosan as thermosensitive in situ gel-forming system for ocular drug delivery

A novel copolymer, poly(N-isopropylacrylamide)-chitosan (PNIPAAm-CS), was investigated for its thermosensitive in situ gel-forming properties and potential utilization for ocular drug delivery. The thermal sensitivity and low critical solution temperature (LCST) were determined by the cloud point method. PNIPAAm-CS had a LCST of 32 degrees C, which is close to the surface temperature of the eye. The in vivo ocular pharmacokinetics of timolol maleate in PNIPAAm-CS solution were evaluated and compared to that in conventional eye drop solution by using rabbits according to the microdialysis method. The C(max) of timolol maleate in aqueous fluid for the PNIPAAm-CS solution was 11.2 microg/ml, which is two-fold higher than that of the conventional eye drop, along with greater AUC. Furthermore, the PNIPAAm-CS gel-forming solution of timolol maleate had a stronger capacity to reduce the intra-ocular pressure (IOP) than that of the conventional eye drop of same concentration over a period of 12 h. In addition, the MTT assay showed that there is little cytotoxicity of PNIPAAm-CS at concentration range of 0.5-400 microg/ml. These results suggest that PNIPAAm-CS is a potential thermosensitive in situ gel-forming material for ocular drug delivery, and it may improve the bio-availability, efficacy, and compliance of some eye drugs.

Timolol transport from microemulsions trapped in HEMA gels

Approximately 90% of all ophthalmic drug formulations are now applied as eye-drops. While eye-drops are convenient and well accepted by patients, about 95% of the drug contained in the drops is lost due to absorption through the conjunctiva or through the tear drainage. A major fraction of the drug eventually enters the blood stream and may cause side effects [J.C. Lang, Adv. Drug Delivery Rev. 16 (1995) 39-43; C. Bourlais, L. Acar, H. Zia, P.A. Sado, T. Needham, R. Leverge, Prog. Retinal Eye Res. 17 (1998) 33-58; M.P. Segal, FDA Consumer Mag. (1991)]. The drug loss and the side effects can be minimized by using microemulsion-laden soft contact lenses for ophthalmic drug delivery [D. Gulsen, A. Chauhan, Invest. Ophthalmol. Vis. Sci. 45 (2004) 2342-2347; D. Gulsen, A. Chauhan, Abstr. Pap. Am. Chem. Soc. 227 (2004) U875]. In order for microemulsion-laden gels to be effective, these should load sufficient quantities of drug and should release it a controlled manner. The presence of a tightly packed surfactant at the oil-water interface of microemulsions may provide barrier to drug transport, and this could be used to control the drug delivery rates. In this paper we focus on trapping ethyl butyrate in water microemulsions stabilized by Pluronic F127 surfactant in 2-hydroxyethyl methacrylate (HEMA) gels and measuring the transport rates of timolol, which is a beta-blocker drug that is used for treating a variety of diseases including glaucoma. The results described here show that microemulsion-laden gels could have high drug loadings, particularly for drugs such as timolol base which can either be dissolved in the oil phase or form the oil phase of the microemulsions. However, the surfactant covered interface of the Pluronic microemulsions does not provide sufficient barrier to impede the transport of timolol, perhaps due to the small size of this drug.

Topical aldose reductase inhibitor formulations for effective lens drug delivery in a rat model for sugar cataracts

PURPOSE

In the topical delivery of drugs to the lens, drug retention on the eye surface is considered to be important because increased retention on the ocular surface should lead to increased ocular absorption of a drug through the cornea into the aqueous humor and subsequently the lens. The aim of this study was to investigate whether increasing the viscosity of a topical aldose reductase inhibitor suspension increases the lenticular bioavailability of the inhibitor and whether such a formulation can arrest sugar cataract formation.

METHODS

Five topical suspensions of 3% 2-methylsorbinil (2-MS) were prepared using (1) hydroxypropyl methylcellulose (HPMC, 0.5% w/v), (2) xanthan gum (0.5% w/v), (3) gellan gum (0.5% w/v), (4) carbopol (0.25% w/v), and (5) carbopol (0.25% w/v)--hydroxypropyl methylcellulose (HPMC) (0.25% w/v). Viscosity measurements were conducted with a viscometer. Lenticular levels of 2-MS were determined in the lenses from young Sprague Dawley rats receiving 1 drop of selected topical suspension twice-daily for 7 days. The efficacy of the suspensions to arrest sugar cataract formation was evaluated by administering the suspensions for 21 days to similar rats fed a diet containing 50% galactose. Lens changes were examined by portable slit lamp following mydriasis.

RESULTS

Lenticular levels of 2-MS was highest in rats administered suspensions containing 0.25% carbopol + 0.25% HPMC as vehicles followed by 0.5% gellan gum, 0.5% HPMC, 0.25% carbopol, and 0.5% xanthan gum. All untreated rats fed a 50% galactose diet developed hypermature cataracts within 15 days; however, none of the topical treated rats demonstrated cortical vacuole formation after 21 days of galactose feeding.

CONCLUSIONS

In the suspensions examined, no direct relationship between the lenticular drug levels of 2-MS and either viscosity or pH of the vehicles were observed. The observed arrest of sugar cataract formation indicated that therapeutically adequate lenticular levels of 2-MS were provided by all topical suspensions.

Formulation of Sirolimus Eye Drops and Corneal Permeation Studies

The aim of this study was the development of eye drops with 1 mg/mL sirolimus and the evaluation of the drug's ability to permeate the freshly isolated pig cornea. Cyclodextrin solutions, liposomes, hydrotrope mixtures, poloxamer gels, and a microemulsion were tested for their suitability to dissolve the extremely hydrophobic drug sirolimus (solubility in water 2.6 microg/mL). The drug content in the formulations was determined by high-performance liquid chromatography, whereas this method is not sensitive enough for the quantification of therapeutic concentrations (7-12 ng/mL). Thus, the acceptor samples of the permeation tests were examined by microparticle enzyme immunoassay. A microemulsion is a suitable vehicle to prepare eye drops with sufficient sirolimus concentrations of 1 mg/mL in a formulation with acceptable tolerance and satisfactory stability over 12 months. However, the drug cannot permeate the intact cornea. After removal of the corneal epithelium, drug concentrations in the acceptor sample reach the lower limit of therapeutical levels. Conclusively, the present sirolimus eye drops might be promising therapeutic tools for the immunomodulatory treatment of ocular surface disorders, such as keratoconjunctivitis sicca, vernal conjunctivitis, or atopical blepharitis. They are not suitable to achieve therapeutic concentrations in the aqueous humour of patients with intact cornea.

Penetration of betaxolol HCL ionic suspension 0.25% and betaxolol HCL solution 0.50% into the aqueous humor

PURPOSE

To determine the intraocular penetration of topical drops of betaxolol HCl 0.25% suspension and betaxolol HCl 0.50% solution into the aqueous humor.

METHODS

Fifteen patients were randomly assigned to receive topical betaxolol HCl 0.25% suspension (n=7) or topical betaxolol HCl 0.50% solution (n=8) the day before cataract surgery. Aqueous samples were collected 2 hours after the administration of the morning dose during cataract surgery. Drug concentrations were determined by high-performance liquid chromatography with fluorescence detection.

RESULTS

The mean aqueous humor concentration of topical betaxolol HCl 0.25% suspension was 275.1+/-168.8 micro g/mL (range 570-70 micro g/mL) and the mean aqueous humor concentration of topical betaxolol HCl 0.50% solution was 195.4+/-102.4 micro g/mL (range 334-50 micro g/mL) (p=0.281).

CONCLUSIONS

The mean aqueous humor concentration of betaxolol 0.25% suspension was higher than betaxolol 0.50% solution; however, the difference was not statistically significant. With twofold reduced concentration and similar anterior chamber penetration, betaxolol 0.25% suspension could be first choice for Beta 1 selective blocker therapy when considered for patients with glaucoma.

Ocular disposition, pharmacokinetics, efficacy and safety of nanoparticle-formulated ophthalmic drugs

Ophthalmic drugs are delivered to ocular tissues predominantly via relatively simple formulations, such as topically dosed water-soluble drug solutions and water-insoluble drug suspensions in ointments. An ideal topical drug delivery system should possess certain desirable properties, such as good corneal and conjunctival penetration, prolonged precorneal residence time, easy instillation, non-irritative and comfortable to minimize lachrymation and reflex blinking, and appropriate rheological properties. In general, ocular efficacy is closely related to ocular drug bioavailability, which may be enhanced by increasing corneal drug penetration and prolonging precorneal drug residence time. To improve ocular bioavailability of topically dosed ophthalmic drugs, a variety of ocular drug delivery systems, such as hydrogels, microparticles, nanoparticles, microemulsions, liposomes and collagen shields, have been designed and investigated. These newer systems may, to some extent, control drug release and maintain therapeutic levels in ocular tissues over a prolonged period of time. This review focuses on the in vitro, ex vivo and in vivo studies of ophthalmic drugs formulated in nanoparticles published over the past two decades. The progress and development issues relating to ocular disposition, pharmacokinetics, efficacy and safety of the nanoparticle-formulated ophthalmic drugs are specifically addressed. Information and discussions summarized in this review are helpful for pharmaceutical scientists to develop better ophthalmic therapeutics.

In Vitro Diffusion of the Immunosuppressant Tacrolimus Through Human and Rabbit Corneas

PURPOSE

The aim of this study was to investigate the in vitro diffusion kinetics of tacrolimus (TAC) through rabbit and human corneas, and to evaluate the suitability of rabbit cornea as an in vitro permeability model for human cornea.

METHODS

A flow-through diffusion apparatus was used for all permeability experiments. The percentage of total (3)H-TAC diffusing across the corneas was determined over 24 h and fractions collected twice-hourly (20 degrees C; 1.5 mL/h). An F test was used for whole-curve comparisons, with a significance level of 5%.

RESULTS

Steady-state values for TAC across both types of corneas were not reached. Although the percentage of TAC diffusing across rabbit cornea was higher than that found for human cornea up to 18 h, there were no statistically significant differences. The percentages of total TAC diffusing across human and rabbit cornea at the 24-h time points were 0.38% +/- 0.02% and 0.36% +/- 0.01%, respectively.

CONCLUSIONS

Percentages of total TAC at the 24-h time points were approximately 4.9x and 4.1x higher than those found previously for cyclosporin A across human and rabbit corneas, respectively. Rabbit corneas are a suitable model for human corneas in in vitro permeability studies.

[The deleterious effect of certain surface active agents on the ocular surface]

Most ocular solutions enter the eye through the corneal epithelial barrier. In order to pass through this barrier, these hydrosoluble drugs require to be associated with a detergent agent to increase topical efficiency. Although these agents have a preservative action, it was recently demonstrated that, after short or long term use, toxic side effects on the ocular surface will occur.

The elution of poly (vinyl alcohol) from a contact lens: The realization of a time release moisturizing agent/artificial tear

The use of a contact lens as a polymeric delivery vehicle is presented. Specifically, the elution of nonfunctionalized poly (vinyl alcohol) (PVA) from nelfilcon A hydrogel lenses is presented as a model of delivering polymeric active agents to the eye. High molecular weight nonfunctionalized PVA is added to the lens matrix for later release into the tears. This is made possible by photo crosslinking a macromer species in lieu of monomeric polymerization. Consistent near zero order release of 0.062% (wt/wt) was demonstrated in vitro over a 20-h period. The result is a new contact lens device based on the slow release of PVA. In vivo results demonstrate that this product improves the wearing comfort of this type of contact lens and acts as a model basis for drug delivery.

Delay in ICR/f Rat Lens Opacification by the Instillation of Eye Drops Containing Disulfiram and Hydroxypropyl-.BETA.-cyclodextrin Inclusion Complex

In this study, we attempted to enhance disulfiram (DSF) solubility using a 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD) and hydroxypropylmethylcellulose (HPMC). We also investigated the effect of an HPbetaCD solution containing DSF and HPMC (DSF eye drops) on cataract development in ICR/f rat. The solubility of DSF increased with increasing HPbetaCD concentration, and the solubility of DSF in HPbetaCD solution containing 0.1% HPMC was approximately 20% greater than that of DSF in HPbetaCD solution without HPMC. In in vivo transcorneal penetration experiments using rabbits, only diethyldithiocarbamate (DDC) was detected (DSF was not detected) in the aqueous humor. This DSF-DDC conversion in the cornea was inhibited by treatment with a sulfhydryl (SH) inhibitor, p-mercuribenzoate and N-ethylmaleimide, in in vitro transcorneal penetration experiments using rabbit corneas. On the other hand, the instillation of 0.25% and 0.5% DSF eye drops delayed cataract development in ICR/f rats, a recessive-type hereditary cataractous strain. The present study demonstrates that DSF in HPbetaCD solution with HPMC is converted to DDC by the catalysis of proteins containing SH residues in the cornea, and this DDC may cause the delay in cataract development in ICR/f rats.

Aqueous humor penetration of gatifloxacin and moxifloxacin eyedrops given by different methods before cataract surgery

PURPOSE

To determine whether the penetration into the aqueous humor of 2 new fourth-generation fluoroquinolone antibiotics, gatifloxacin (Zymar) and moxifloxacin (Vigamox) eyedrops, was affected by different methods of administration before cataract surgery.

SETTING

Pasqua Hospital, Regina, Saskatchewan, Canada.

METHODS

This prospective randomized study comprised 193 patients. The patients were divided into 2 main groups. One group received gatifloxacin eyedrops and the other, moxifloxacin eyedrops. Each group was subdivided into 4 subgroups. All patients received the drops 4 times a day starting 2 days preoperatively. The first subgroup did not receive any more antibiotics. The second subgroup received the antibiotic drops 3 times, starting approximately 2 hours preoperatively. The third subgroup received a wick soaked in a dilating mixture containing the antibiotic. The fourth subgroup received the wick and the antibiotic drops at the time of preparation for surgery. At the beginning of surgery, 0.1 mL of aqueous humor was aspirated, frozen, and sent under ice by courier to the Provincial Laboratory for analysis by high-performance liquid chromatography.

RESULTS

The study included 124 women and 69 men. The mean concentrations in the aqueous humor were 0.19, 0.82, 0.22, and 0.30 microg/mL in the 4 gatifloxacin subgroups, respectively, and 0.38, 2.16, 0.88, and 0.97 microg/mL in the 4 moxifloxacin subgroups, respectively. Analysis of variance showed the differences between the 2 antibiotics to be statistically significant.

CONCLUSIONS

Moxifloxacin penetrated the aqueous humor better than gatifloxacin regardless of the method of administration. Both antibiotics penetrated the aqueous humor well when given in drop form. They reached and exceeded the minimum inhibitory concentration levels for the most common ocular pathogens causing endophthalmitis. Only moxifloxacin reached these levels when the wick was used.

Preoperative ketorolac tromethamine 0.4% in phacoemulsification outcomes: pharmacokinetic-response curve

PURPOSE

To assess the clinical benefit, relative efficacy, and pharmacokinetic-response curve of preoperative and postoperative ketorolac tromethamine 0.4% (Acular LS) to improve outcomes during and after cataract surgery.

SETTING

Private clinical practice.

METHODS

One hundred patients were randomized in a double-masked fashion to 4 groups of 25 to receive ketorolac for 3 days, 1 day, or 1 hour or a placebo before phacoemulsification. All treatment groups received ketorolac 0.4% for 3 weeks postoperatively; the placebo group received vehicle. Outcomes measures were preservation of preoperative mydriasis, phacoemulsification time and energy, operative time, corneal clarity, endothelial cell counts, postoperative inflammation, intraoperative and postoperative discomfort, complications, and incidence of clinically significant cystoid macular edema (CME).

RESULTS

Maintenance of pupil size with 3-day ketorolac dosing was significantly better than with 1-day dosing (P<.01), which was significantly better than with 1-hour or placebo dosing (P<.01). Both 3-day and 1-day dosing were superior to 1-hour or placebo dosing. No patient receiving ketorolac 0.4% for 1 or 3 days developed CME compared with 12% of patients in the control (placebo) group and 4% in the 1-hour group. Three-day and 1-day dosing of ketorolac reduced surgical time, phacoemulsification time and energy, and endothelial cell loss and improved visual acuity in the immediate postoperative period compared with 1-hour predosing and the placebo (P<.05).

CONCLUSION

The preoperative use of ketorolac tromethamine 0.4% for 3 days followed by 1-day of predosing provided optimum efficacy and superior outcomes relative to 1-hour pretreatment and a placebo.

Topical brimonidine 0.2%/timolol 0.5% ophthalmic solution: in glaucoma and ocular hypertension

A fixed combination of brimonidine (a highly selective alpha(2)-adrenergic agonist) and timolol (a non-selective beta-blocker) [brimonidine 0.2%/timolol 0.5% ophthalmic solution; brimonidine/timolol] is available for the topical treatment of glaucoma and ocular hypertension (OH). Brimonidine and timolol decrease elevated intraocular pressure (IOP) by complementary mechanisms of action and have an additive effect when coadministered to healthy volunteers and patients with glaucoma or OH. When assessed over a 3- or 12-month period in large, well designed clinical studies, brimonidine/timolol instilled twice daily (one drop in each eye) was superior to monotherapy with the individual components instilled two (brimonidine) or three (timolol) times daily, and noninferior to concomitant therapy with the individual components instilled twice daily, in lowering raised IOP in patients with glaucoma or OH. In small, randomised, comparative studies of 1 or 3 months' duration, the IOP-lowering effect of brimonidine/timolol twice daily was similar or superior to that of fixed combination dorzolamide 2%/timolol 0.5% ophthalmic solution (dorzolamide/timolol) twice daily (preliminary data). Brimonidine/timolol is generally well tolerated with a predictable local and systemic adverse event profile based on that of the individual components used alone and concomitantly. No unexpected or serious adverse events associated with the fixed combination were reported in key clinical trials. Brimonidine/timolol may be advantageous over dorzolamide/timolol with respect to ocular tolerability and comfort (preliminary data).

Vitreous Concentration of Topically Applied Brimonidine-Purite 0.15%

PURPOSE

The aim of this study was to determine the vitreous brimonidine concentration of topically applied brimonidine-Purite 0.15%.

METHODS

Patients scheduled for a pars plana vitrectomy were invited to participate in this study after institutional review board (IRB) approval was obtained. Each patient was asked to apply brimonidine-Purite (0.15%) drops in the designated eye either every 12 h (b.i.d.; 9 patients) or every 8 h (t.i.d.; 10 patients) for the 2 weeks proceeding scheduled surgery. The importance of the last topical dose being 12 h (b.i.d. group) or 8 h (t.i.d. group) before the scheduled surgery, was emphasized. Four (4) patients served as controls and did not receive any drops. Vitreous (approximately 0.5-1.0 mL) was aspirated prior to opening the infusion line. Specimens were frozen at -68 degrees C until analyzed.

RESULTS

In the b.i.d. group, the mean concentration of brimonidine was 16.74 nM+/-10.33 standard deviation (range, 0.42-34.68 nM; median, 16.38); in the t.i.d. group, the mean concentration of brimonidine was 19.16 nM+/-15.40 standard deviation (range, 0.22-39.48 nM; median, 16.98). A significant difference was observed between the (no drug) control vitreous brimonidine levels and b.i.d. or t.i.d. vitreous levels (P<0.01, <0.01, respectively; n=4, 9, and 10, respectively); and in brimonidine levels between t.i.d. phakic patients and t.i.d. patients with posterior chamber lens (P=0.04; n=4 and 6, respectively).

CONCLUSIONS

Brimonidine-Purite 0.15%, topically applied b.i.d. or t.i.d. for 2 weeks prior to collection, acquired vitreous levels of brimonidine at or above the 2-nM concentration known to activate the neuroprotective alpha-2 receptor in animals.

Pharmacokinetics of Chlorhexidine Gluconate 0.02% in the Rabbit Cornea

PURPOSE

The aim of this study was to determine the pharmacokinetic parameters of chlorhexidine gluconate (CHG) in the rabbit cornea.

METHODS

Each eye of 16 New Zealand white rabbits were topically instilled with 50 microL of CHG 0.02% eye drops twice with a 5-min interval. Four (4) corneas of 2 rabbits were harvested at each time point. The concentration of CHG in the cornea was determined with high-performance liquid chromatography (HPLC) and 387 software to simulate the pharmacokinetic parameters.

RESULTS

The concentration of CHG in the cornea displayed an open two-compartment model. Tmax was 13.75 min, Cmax 0.713 microg.g1, clearance rate 1.64 microg.g-1.min-1, and t1/2alpha, t1/2beta, and t1/2ka was 2.65, 48.72, and 2.67 min, respectively.

CONCLUSIONS

The concentration of CHG in the rabbit cornea could be determined by means of HPLC. The maximum concentration of CHG in the corneal tissue was much higher than the trophozoite minimum amoebicidal concentration (TMAC) in vitro.

Effect of formulation factors on in vitro transcorneal permeation of gatifloxacin from aqueous drops

The purpose of this research was to optimize the formulation factors for maximum in vitro permeation of gatifloxacin from aqueous drops through excised goat cornea and to evaluate the permeation characteristics of drug from selected marketed eyedrop formulations. Permeation studies were conducted by putting 1 mL of formulation on the cornea (0.67 cm(2)) fixed between the donor and receptor compartments of an all-glass modified Franz diffusion cell and measuring gatifloxacin concentration in the receptor (containing normal saline under stirring) by spectrophotometry at 291.5 nm, after 120 minutes. Raising the drug concentration of the drops increased the drug permeation but decreased the percent permeation and the in vitro ocular availability. Raising the pH of the formulation from pH 5 to 7.2 increased both the drug permeation and the in vitro ocular availability. Eyedrops containing benzalkonium chloride (BAK; 0.01% wt/vol) and disodium edetate (EDTA; 0.01% wt/vol) showed maximum permeation, followed by Zymar, BAK (0.01% wt/vol), Gatilox, Gatiquin, and Gate (statistically significant P < .05 compared with control). In vitro titration of the formulations with 0.1N NaOH indicated the presence of a buffer in Zymar (pH 6) and Gate (pH 5.8), which may cause irritation and induce lacrimation, resulting in reduced ocular availability in vivo. Thus, formulation with BAK and EDTA, which is unbuffered, has a better likelihood of being absorbed in vivo. The BAK-EDTA formulation significantly (P < .05) increased the permeation of gatifloxacin through paired excised corneas of goat, sheep, and buffalo, compared with the control formulation. The goat cornea showed the greatest increase in permeation, followed by the sheep and buffalo corneas.

The Interaction and Compatibility Between a Soft Contact Lens and an Ophthalmic Drug

PURPOSE

To investigate the interaction and compatibility between a soft contact lens (SCL) and an ophthalmic drug.

METHODS

Samples were prepared with the nonionic SCL (groups I and II), the anionic SCL (group IV), and the zwitter ionic SCL (group IV). Chlorpheniramine maleate and sodium cromoglycate were used to measure the drug uptake into the SCL.

RESULTS

The results showed the largest drug uptake into the anionic SCL accompanied with dimensional changes and lower drug uptakes into the nonionic and the zwitter ionic SCL with dimensional stability. The cell permeability of the substances when instilled in the eye over the SCL was also measured. The zwitter ionic SCL allowed cell permeability comparable to that by oral administration.

CONCLUSIONS

These results indicated the possibility for the zwitter ionic SCL as a lens to be worn concomitantly with ophthalmic drug instillation.

[The effects of amniotic membrane on corneal penetration of ofloxacin]

OBJECTIVE

To evaluate the corneal penetration of ofloxacin following amniotic membrane transplantation (AMT).

METHODS

One hundred and eight New Zealand rabbits were divided into 6 groups: mechanical remove of corneal epithelium with and without AMT; corneal alkali burn with and without AMT, and normal cornea with and without AMT. Topical ofloxacin was administered four times at interval of every 15 minutes. Five min, 30 min, 1 h, 2 h, 4 h and 6 h after the last administration, 3 rabbits from each group were sacrificed and aqueous humor was collected. The concentration of ofloxacin was detected by high pressure liquid chromatography (HPLC).

RESULTS

The ability of ofloxacin to penetrating cornea was improved obviously in de-epithelialized groups and cornea alkali burn groups no matter AMT was performed or not (P < 0.05). The concentration of ofloxacin in the aqueous humor in normal cornea with and without AMT showed no statistical difference within 1 h after administration. But at the last three time points, the ofloxacin concentration in AMT group was greater than that in the group without AMT (P < 0.05). The comparison between the de-epithelialized with and without AMT obtained the similar result. At every tested time point, the ofloxacin concentration in aqueous humor of corneal alkali burn with AMT group was statistically greater than that of the group without AMT (P < 0.05).

CONCLUSION

Amniotic membrane could store and release the drug slowly, results in the increase of contact time between ofloxacin and corneal surface and promotes the corneal penetration of ofloxacin.

[Ocular pharmacokinetics and bioavailability of 0.2% ganciclovir in-situ gelling eye drops]

OBJECTIVE

To compared the pharmacokinetics and bioavailability of 0.2% ganciclovir (GCV) in-situ gelling eye drops (GCV-ISG) with common GCV eye drops (GCV-ED) in rabbits.

METHODS

Forty-eight healthy albino rabbits were randomly divided into 2 groups, each group included 24 rabbits and 3 rabbits (6 eyes) were used at each time points. Each eye received 50 microl of GCV-ISG in experimental group, and the same amount of GCV-ED was given in the other group as the control. The tears and aqueous humors were collected at 5, 10, 15, 30, 45, 60, 90 and 120 minutes following topical application of GCV-ISG and GCV-ED, respectively, and the corneas were immediately dissected after euthanized. The samples from 6 eyes (3 animals) were obtained at each designed time point. All samples were stored -60 degrees C and then were assayed by reversed phase high performance liquid chromatography (HPLC). An unpaired Student's t-test and 3p97 pharmacokinetics software were used as statistical analysis.

RESULTS

The drug levels in tears corneas and aqueous were significantly higher for GCV-ISG group than GCV-ED group at 5, 10 minutes (P < 0.05) and 120 minutes (P < 0.01). The areas under the curve (AUC0-120) of the drug concentrations versus times in tears, corneas and aqueous humors for GCV-ISG group were 2.22, 5.47 and 3.40 times as high as GCV-ED group within designed duration, respectively. The peak concentrations of GCV in aqueous humors for GCV-ISG group and the GCV-ED group were 4.79 microg/ml and 0.96 microg/ml, respectively. The half-lives of GCV in aqueous humors and corneas for GCV-ISG group were 59 minutes and 223 minutes, and for GCV-ED group were 43 minutes and 87 minutes, respectively. The peak concentration of GCV in aqueous humor in GCV-ISG group was 4.99 times higher than that in GCV-ED group (P < 0.01).

CONCLUSIONS

0.2% ganciclovir in-situ gelling eye drops significantly increases the drug penetration into cornea and aqueous humor, and prolongs the residence time in cornea and aqueous humor. The results suggest that 0.2% ganciclovir in-situ gelling eye drops may enhance the ocular bioavailability of ganciclovir in rabbit eye.