Effect of concurrent topical corticosteroid and NSAID therapy of experimental keratitis

The ability of suprofen, a nonsteroidal anti-inflammatory drug, and prednisolone acetate, a corticosteroid, to suppress polymorphonuclear leukocyte invasion of the rabbit cornea during an experimental keratitis was evaluated following topical ophthalmic administration of either drug alone or both drugs concurrently. Suprofen therapy initiated immediately after induction of inflammation was ineffective. However, if suprofen therapy was begun 48 hr prior to the induction of inflammation, the drug was effective. In contrast, prednisolone acetate therapy begun after the induction of inflammation was effective; 48 hr of pretreatment with the corticosteroid produced a marked increase in its therapeutic effect. When administered according to the same regimen, concurrent therapy with suprofen and prednisolone acetate was significantly more effective than treatment with either drug alone. This result was obtained irrespective of whether concurrent therapy was initiated prior to or after the inflammatory event.     

Intraocular penetration of ketoconazole in rabbits.

We studied penetration of the antifungal agent ketoconazole into the cornea, aqueous humor, and vitreous of rabbits after topical, subconjunctival, and oral administration. The effect of debridement of corneal epithelium on penetration was also investigated. Ketoconazole levels in the cornea and aqueous humor were high after topical or subconjunctival administration, and increased markedly (especially in the cornea) if the corneal epithelium had been debrided before administration of the drug. For example, concentration of ketoconazole in the cornea 1 h after topical drug administration with or without complete corneal epithelial debridement was 44.0 +/- 10.1 and 1,391.5 +/- 130.0 micrograms/g, respectively. Drug levels in the vitreous were not detectable after topical or subconjunctival drug administration, but were improved slightly by prior epithelial debridement (8.3 and 0.12 micrograms/mL after 1 h, respectively). Orally administered ketoconazole resulted in high corneal concentrations (45.0 +/- 7.6 micrograms/g after 1 h) that were still substantial 24 h later (55.0 +/- 7.0 micrograms/g); levels in the aqueous were low.     

硝酸益康唑纳米粒在兔眼内的药代动力学研究

背景 硝酸益康唑因眼内的通透性差而影响其在眼部的抗真菌效果,通过改变硝酸益康唑的剂型增加其眼内通透性成为目前研究的热点. 目的 研究质量分数0.5％硝酸益康唑纳米粒溶液点眼后的眼部通透性及眼部药代动力学.方法 采用溶剂扩散法制备0.5％硝酸益康唑纳米粒,透射电子显微镜下观察纳米粒性状,激光散射法测定纳米粒的大小.收集27只新西兰大白兔双眼点0.5％硝酸益康唑纳米粒滴眼液后,分别于点眼后5、15、30、45、60、90、120、180、240 min抽取大白兔房水100μl,然后处死动物获取角膜组织,制备角膜组织匀浆.用反相高效液相色谱法( HPLC)定量测定房水和角膜样本中硝酸益康唑的质量浓度和质量分数,采用3 p97药代动力学软件进行计算机拟合求得0.5％硝酸益康唑纳米粒溶液点眼后眼部的药代动力学参数. 结果 所制备的硝酸益康唑纳米粒的平均粒径为50.1 nm,形状均匀圆整,包封率为96.0％.采用反相HPLC法可以将硝酸益康唑同其他杂质分离,最低定量质量浓度为0.1 mg/L,硝酸益康唑在角膜中的平均回收率为98.09％;在房水中平均回收率为99.66％.各时间点房水及角膜组织中均可检测出硝酸益康唑,其中角膜组织中和房水中均于点眼后5 min时质量分数和质量浓度达最高,分别为(40.620±7.756) μg/g和(0.504±0.153) mg/L,在角膜和房水中的消除半衰期(t1/2)分别为23.5 min和18.6 min.结论 0.5％硝酸益康唑纳米粒点眼可使药物在角膜和房水中达到有效的药物质量分数和质量浓度.     

Ocular absorption and distribution of loteprednol etabonate, a soft steroid, in rabbit eyes

Loteprednol etabonate (LE) is a "soft" steroid belonging to a unique class of glucocorticoids. LE possesses a metabolically labile 17 beta-chloromethyl ester function which was designed in order to be hydrolyzed to an inactive carboxylic acid moiety. The ocular absorption and metabolism of a 14C-labelled LE was evaluated in New-Zealand White rabbits after administration of a 0.5% suspension in both eyes. At various time points following ocular administration, the cornea, aqueous humor, and iris-ciliary body were collected. LE and the putative inactive metabolites, PJ-90 and PJ-91, were identified in all 3 tissues. Levels of LE and its metabolites were highest in the cornea, and so was the ratio of metabolites to unchanged drug, suggesting that the primary site of deactivation of the drug is the corneal tissue. A substantial amount of metabolites were also detected in the iris-ciliary body, although to a lesser extent than in the cornea. The amount of drug and metabolites in the aqueous humor was very low. It is concluded that LE is indeed a soft steroid with good ocular permeation properties.     

两性霉素B经三种途径给药后在角膜和房水中药物浓度的实验研究

背景角膜基质内注射或前房内注射两性霉素B治疗顽固的真菌性角膜炎取得较好疗效，但通过这2种途径给药后，药物在角膜和房水的浓度变化尚不清楚。目的探讨质量分数0．25％两性霉素B滴眼液点眼、1％两性霉素B注射液角膜基质内注射及1％两性霉素B注射液前房内注射3种途径给药后兔眼角膜和房水中的药物质量浓度变化。方法健康家兔45只按随机数字表法分为A、B、C3组，每组15只。A组、B组分别在角膜基质内和前房内单次注射10¨g两性霉素B注射液，C组兔眼机械法去除角膜上皮后用0．25％两性霉素B滴眼液点眼，每次50仙l，共6次，每次间隔5rain。分别于用药后30min、6h、1d、3d、7d各处死3只实验兔，获取房水和角膜组织，采用高效液相色谱法进行两性霉素B质量浓度的定量检测。结果在质量浓度0．10～100．00mtg／L范围内，两性霉素B的峰面积与吸收度之间具有良好的线性关系；0．10mg／L为其定量限质量浓度；药物在房水的回收率为89．1％～95．7％，在角膜中为81．4％～83．6％。用药后30rain、6h、1dA组角膜中的药物质量分数高于B组及C组，差异均有统计学意义（P〈0．05），高药物质量浓度可持续7d，超出绝大多数敏感真菌的MIC。。。用药后30min、6h、1dB组兔眼房水中的药物质量浓度高于A组及C组，差异均有统计学意义（P〈0．05）。C组1d内角膜和房水中均检测到明显药物浓度。结论兔眼角膜基质内注射及前房内注射两性霉素B可以提高药物在角膜及房水中的质量浓度，清除角膜上皮可以提高两性霉素B的角膜穿透力。     

Ocular bioavailability of ciprofloxacin in sustained release formulations.

A novel sustained release delivery system of ciprofloxacin for the eye was developed. The system consists of a viscosity enhancer (carbopol gel or hydroxypropylmethylcellulose solution) plus a penetration enhancer (dodecylmaltoside) to overcome penetration barriers and loss due to wash-out and thus achieve the desired ciprofloxacin ocular absorption. The present studies were designed to assess the ocular penetration and bioavailability of ciprofloxacin in sustained release formulations. In vitro studies in rabbits indicated an approximate 10-fold increase in drug penetration through the rabbit cornea using the penetration enhancer, dodecylmaltoside. In vivo bioavailability studies demonstrate that these formulations provided a long drug duration in the cornea. After administration of a single topical dose of ciprofloxacin (0.3%/30 microL), corneal levels greater than the Minimum Inhibitory Concentration (MIC90) (0.5 microg/g) were observed through eight hours. These sustained release formulations delivered 10-fold more drug into the aqueous humor than the standard solution formulation. Maximum ciprofloxacin concentrations in the aqueous humor (0.5-0.7 microg/mL) were attained between one and two hours after dosing. Using these sustained release formulations, ciprofloxacin can penetrate to the anterior chamber of the eye in concentrations that are inhibitory for most gram-negative and gram-positive organisms. These topical ocular formulations have prophylactic utility for prevention of post-surgical infection, offering greater efficacy and safety than currently available treatments.     

羊膜对氧氟沙星滴眼液兔角膜通透性的影响

目的探讨羊膜对氧氟沙星滴眼液兔角膜通透性的影响。方法先给108只新西兰大白兔进行样本编号,再按号码单纯随机抽样并分为6组,每组18只,分别为正常角膜组、正常角膜羊膜移植组、机械刮除角膜上皮组、机械刮除上皮联合羊膜移植组、角膜碱烧伤组、角膜碱烧伤联合羊膜移植组。0．3％氧氟沙星眼液滴眼,每15min滴眼1次,共4次,最后1次滴眼后5、30min,1、2、4、6h,于每个时间点每组18只大白兔中任意处死3只兔抽取房水。高效液相法检测房水中氧氟沙星的浓度。结果刮除角膜上皮组与正常角膜上皮组比较,药物的前房浓度均明显增高（均P〈0．05）。正常角膜羊膜移植组5、30min、1h房水中氧氟沙星浓度与正常角膜组无明显差异（均P〉0．05）,而2、4、6h则明显高于正常角膜组（均P〈0．05）;机械刮除上皮联合羊膜移植组2、4、6h房水中氧氟沙星浓度亦明显高于机械刮除角膜上皮组（均P〈0．05）,而两组间5、30min、1h房水中氧氟沙星浓度比较无明显差异（均P〉0．05）;角膜碱烧伤联合羊膜移植组6h以内房水中氧氟沙星浓度均高于碱烧伤组（均P〈0．05）。结论羊膜具有一定药物蓄积和缓释作用,增加了氧氟沙星在角膜表面的停留时间,使药物的通透性增高。     

Corneal absorption and anterior chamber pharmacokinetics of dipeptide monoester prodrugs of ganciclovir (GCV): in vivo comparative evaluation of these prodrugs with Val-GCV and GCV in rabbits.

AIM: The overall aim of this study was to evaluate the corneal absorption of dipeptide monoester prodrugs of ganciclovir (GCV) and compare these results with L-valine-GCV and GCV. Another aim was to evaluate the pharmacokinetics of these prodrugs in aqueous humor. METHODS: A well was placed on the cornea of anesthetized New Zealand albino rabbits with linear probes implanted in the aqueous humor. Two hundred microlitres (200 microL) of a 0.43% w/v (saturation concentration) solution of GCV and equimolar concentrations of its prodrugs, VGCV, glycine-valine-GCV (GVGCV), valine-valine-GCV (VVGCV), and tyrosine-valine- GCV (YVGCV), were placed in the corneal well and were allowed to diffuse for a period of 2 h. Subsequently, the drug solution was aspirated and the well removed. Samples were collected every 20 min throughout the infusion and postinfusion phases and were analyzed by high-performance liquid chromatography to determine the aqueous humor concentrations. RESULTS: Area under the concentration time profile (AUC)infinity and maximum concentration (Cmax) of YVGCV were found to be higher than other prodrugs. AUC of total GCV obtained from YVGCV administration was found to be twelvefold more than AUC of GCV and 6.2-fold more than AUC obtained with total GCV from VGCV administration. VVGCV also exhibited 3.2 times higher AUC relative to VGCV. Also, AUC and Cmax of regenerated GCV from YVGCV was 8.6 and 4.9 times more than GCV, respectively. VVGCV did not produce higher concentrations of GCV. Elimination half-life of regenerated GCV from YVGCV administration was observed to be 157 min. CONCLUSIONS: YVGCV and VVGCV exhibited superior corneal absorption and bioavailability, in comparison with GVGCV, VGCV, and GCV. Such facilitated absorption of prodrugs may be a result of a combination of transcellular passive diffusion and peptide transporter (PEPT1)-mediated transport across the corneal epithelium.     

Disposable 1-day Acuvue contact lenses for the delivery of lomefloxacin to rabbits' eyes.

PURPOSE: To investigate the ability of a disposable soft contact lens (1-Day Acuvue) to deliver lomefloxacin, a fluoroquinolones antibiotic, into the cornea and aqueous humor of rabbits. METHODS: Experiments were conducted on adult albino rabbits. 1-Day Acuvue lenses were immersed for 1 hour in commercially-available lomefloxacin eye solution and then placed on the cornea. After 0.5, 2, 4,6, and 8 hours, the animals were killed and the lenses were removed and placed into a 20 mL saline bath. Corneal tissue and aqueous humor samples were also obtained at these times. The release of lomefloxacin from the lenses was calculated by measuring the amount of drug remaining in the lenses after removal from the rabbit eyes. The concentration of lomefloxacin in the cornea and anterior chamber following the wearing of lomefloxacin-loaded lenses was compared with the concentrations following frequent-drop therapy (one drop of lomefloxacin hourly for 8 hours). RESULTS: In vivo, lomefloxacin was released from 1-Day Acuvue lenses gradually over 8 hours. The cornea and aqueous humor levels in the eyes following the wear of lomefloxacin-loaded lenses were significantly higher than those achieved by frequent-drop therapy. The drug levels in the cornea and aqueous humor generally remained above the 90% minimal inhibitory concentration for 8 hours in the 1-Day Acuvue lens group. CONCLUSIONS: 1-Day Acuvue contact lenses soaked in 0.3% lomefloxacin can release sufficient amounts of lomefloxacin and in this study produced higher levels in both the cornea and aqueous humor than that achieved by frequent-drop therapy for up to 8 hours. We conclude that 1-Day Acuvue contact lens can be used as a drug delivery system for lomefloxacin.     

Corneal sequestration and delivery to ciliary process of six topically applied sulfonamides.

The accession to cornea, aqueous humor and ultimately ciliary process was studied for a series of 6 sulfonamides which differed in their free acid lipophilicities. The drugs were applied as 5 mM solutions at pH 5 in unionized form or in chiefly ionized form at pH 8.4-9.4. These latter solutions contained 10% unionized drug. At 30 minutes post dose corneal drug levels were 2-3 fold higher for ionized compared to unionized application for a given drug. For ionized application there was a direct correlation between corneal drug accumulation and the lipophilicity of the unionized form of the drug. Cornea and aqueous humor drug levels were nearly equal 30 minutes following unionized application but significantly higher in cornea compared to aqueous humor after ionized application, suggesting drug was being retained in the cornea in ionized form. The efficiency of drug accession to ciliary process from cornea was assessed for the different drugs. The greatest accession to ciliary process from cornea as measured by the ratio of the two drug levels was found to correspond to compounds with free acid CHCl3/buffer partition coefficients approximately equal to unity. These results are discussed in terms of possible pathways of drug diffusion in the eye and the known intraocular pressure effects of topically applied sulfonamides.     

胰岛素对兔角膜碱烧伤早期组织病理学及白细胞介素表达的影响

目的观察胰岛素对兔角膜碱烧伤后角膜组织病理学的变化以及对白细胞介素（IL）表达的影响,并探讨胰岛素在角膜碱烧伤后早期的抗炎机制。方法选取45只健康雌性新西兰白兔,随机分为生理盐水组、地塞米松组和胰岛素组,每组15只。应用浸有1mol/LNaOH溶液的滤纸贴附于角膜中央建立Ⅱ°角膜碱烧伤模型,建模后即日起各组分别于球结膜下注射生理盐水、地塞米松和胰岛素各75μL/（kg.d）,于实验后1、3、7d收集每只动物心脏血3mL和每只眼200μL房水,分别用ELISA法检测实验动物血清和房水中IL-1β的质量浓度的变化,应用逆转录聚合酶链反应（RT-PCR）法检测角膜组织中IL-10mRNA浓度的变化,并对角膜组织进行组织病理学检查,观察角膜组织的形态变化。结果角膜碱烧伤后第1天生理盐水组、地塞米松组和胰岛素组均可见角膜上皮缺失、基质层严重水肿和角膜组织大量炎性细胞浸润;碱烧伤后第3天3组角膜上皮和基质损伤均有不同程度的修复,至第7天生理盐水组角膜基质仍水肿,但地塞米松组和胰岛素组角膜基质层水肿基本消退。角膜碱烧伤后第1、3、7天,3组实验兔血清和房水中的IL-1β质量浓度明显高于正常兔,但地塞米松组和胰岛素组实验兔血清和房水中的IL-1β质量浓度明显低于生理盐水组,差异均有统计学意义（P〈0.01）,第3天、第7天地塞米松组和胰岛素组血清和房水中的IL-1β质量浓度的变化差异均无统计学意义（P〉0.05）。角膜碱烧伤后各时间点地塞米松组和胰岛素组角膜组织中IL-10mRNA浓度明显高于生理盐水组,差异均有统计学意义（P〈0.01）,但地塞米松组和胰岛素组间的差异无统计学意义（P〉0.05）,实验后第3天、第7天地塞米松组和胰岛素组角膜组织中IL-10mRNA浓度均明显高于第1天,差异均有统计学意义（P〈0.01）。结论角膜碱烧伤早期胰岛素可以通过减少促炎性因子的表达、提高抑制炎性因子含量的机制起到抗炎作用,促进角膜损伤的修复。胰岛素的抗炎作用类似于地塞米松。     

Sodium hyaluronate as an ophthalmic vehicle: some factors governing its effect on the ocular absorption of pilocarpine

Sodium hyaluronate, as an additive to aqueous ophthalmic formulations, has been claimed to increase the ocular contact time and, thereby, the drug bioavailability. In the present study, the effect of sodium hyaluronate on corneal residence time and drug absorption in rabbits was investigated. Addition of sodium hyaluronate (0.125%) to a 3H-pilocarpine HCl solution resulted in increased retention of radioactivity in tear fluid and a 2-fold increase in drug concentration in the cornea and aqueous humor. Further, the effects of concentration and molecular weight of sodium hyaluronate on the miosis induced by pilocarpine in rabbits were studied. A significant increase of miotic response was seen at concentrations just less than 0.1% sodium hyaluronate. Pilocarpine solutions prepared from high mol.wt. sodium hyaluronate exhibited a greater miotic response than those prepared from lower mol.wt. samples. This might indicate that other physicochemical properties of sodium hyaluronate influence drug bioavailability.     

Delivery of fluorescein to the anterior chamber using the corneal collagen shield

Collagen corneal shields show promise as an alternative method of drug delivery to the eye. The authors quantified collagen shield delivery of sodium fluorescein to the aqueous humor in human volunteers using fluorophotometry. Collagen shields that had been immersed in 0.01% sodium fluorescein were applied to eyes of human volunteers. The shields delivered significantly more fluorescein to the aqueous humor at 2 and 4 hours compared with drops of the same concentration instilled every 30 minutes for 4 hours (P less than 0.0001 and P = 0.0003, respectively) or daily wear soft contact lenses presoaked in 0.01% fluorescein (P less than 0.0001 and P less than 0.0025, respectively). Collagen shields did not induce damage to the corneal epithelium over a 2-hour wearing period. These results suggest that the collagen shield may be superior to topical drops in delivering water-soluble compounds to the cornea and aqueous humor.     

AL-2512, a novel corticosteroid: preclinical assessment of anti-inflammatory and ocular hypertensive effects.

The anti-inflammatory efficacy and ocular hypertensive effect of AL-2512 were characterized in rodent and feline models of ocular inflammation. Neutrophil influx into ocular tissue following topical ocular administration of test drugs was evaluated in models of endotoxin-induced uveitis. In rats, the anti-inflammatory efficacy of AL-2512 was compared with that of 0.1% dexamethasone. Test drug or vehicle was administered topically before subplantar injection of endotoxin. Neutrophil influx was assessed at 24 hours. Feline eyes, injected intravitreally with endotoxin, were treated topically with 0.1% AL-2512, 1.0% prednisolone acetate or vehicle at various timepoints before and after endotoxin injection. At 12 hours, protein concentration and leukocyte count in aqueous humor were determined. In the feline intraocular pressure (IOP) model, after baseline IOP values were established, AL-2512, dexamethasone, or vehicle was administered topically to both eyes of cats. IOP was measured daily before and during treatment. Topical ocular administration of AL-2512 inhibited endotoxin-induced leukocyte influx in rodent and feline models of uveitis. In rats, AL-2512 significantly inhibited neutrophil influx by 89%, compared with 93% by dexamethasone. In feline eyes, AL-2512 significantly (p < 0.05) inhibited leukocyte infiltration of aqueous humor by 59%, compared to 37% inhibition by prednisolone acetate. Intraocular pressure in cats treated for 32 days with AL-2512 or dexamethasone increased 6% and 18%, respectively. The ocular anti-inflammatory effect of AL-2512 was equivalent to dexamethasone and superior to prednisolone acetate in rat and feline models of ocular inflammation, respectively. This steroid provides anti-inflammatory efficacy equivalent to dexamethasone with a reduced risk of inducing ocular hypertension.     

兔眼局部应用两性霉素B缓释制剂的研究

目的探索兔眼局部应用两性霉素B脂质体（AmBL）和两性霉素B卡波姆（AmBC）滴眼液后，房水中的药代动力学状况。方法用32只新西兰白兔，在角膜上皮完整和刮除时，分别应用0．5％AmBL或0．5％AmBC滴一眼，并用0．5％两性霉素B滴眼液（AmBS）滴对侧眼作对照，分别在用药后0．25、0．5、1、2、3、4h6个时点，抽取兔眼房水，用HPLC方法测定房水中两性霉素B的质量浓度。结果AmBL滴眼后，房水中AmB的有效抑菌浓度可维持2h，AmBC和AmBS滴眼1h后即近全部消除。角膜上皮完整时，AmBL的药效曲线下面积（AUC）和药物半衰期（T1/2）是AmBS的3．6倍和5倍；角膜上皮刮除后，AmBL的AUC和T1/2是AmBS的3．9倍和3．2倍。AmBC的AUC和T1/2与AmBS相似。结论AmBL具有较好的缓释作用和生物利用度，是较有前途的局部治疗真菌性角膜炎的新型缓释制剂。     

Regional ocular gentamicin levels after transcorneal and transscleral iontophoresis

Transcorneal and transscleral iontophoresis were compared to subconjunctival injection (control) in the delivery of gentamicin into rabbit eyes. Gentamicin levels in the corena, aqueous, and vitreous were measured by a fluorescence polarization assay at various time intervals after treatment. A mean peak corneal concentration of 376.1 micrograms/ml was achieved 2 hr after transcorneal iontophoresis. This was significantly higher than the level obtained in control eyes (P = 0.016). A mean peak aqueous humor concentration of 54.8 micrograms/ml occurred 2 hr after transcorneal iontophoresis. This was significantly higher than the peak level of 14.2 micrograms/ml after subconjunctival injection (P = 0.003). Inhibitory levels (approximately 5 micrograms/ml) were maintained in both aqueous and cornea for 8 hr after transcorneal iontophoresis. After transscleral iontophoresis, the mean peak vitreous humor concentration was 53.4 micrograms/ml at 16 hr and remained inhibitory through 24 hr; the peak aqueous level was 23.2 micrograms/ml and remained inhibitory for 24 hr. Peak drug concentrations in the vitreous were significantly higher than control (P = 0.026). Therapeutic vitreous humor levels were not achievable after transcorneal iontophoresis or subconjunctival injection. Potential corneal toxicity of transcorneal iontophoresis was demonstrated by measuring corneal thickness and endothelial cell counts prior to and 3 days after transcorneal iontophoresis of gentamicin and balanced saline solution (BSS) (control). No significant differences existed between eyes treated with gentamicin compared to those treated with BSS or when pre- versus postiontophoresis of gentamicin in the same eyes were compared. Transcorneal and transscleral iontophoresis may be an effective noninvasive method of delivering inhibitory levels of gentamicin to the cornea, aqueous humor, and vitreous for the treatment of intraocular infections.     

Effects of calcium chelating agents on corneal permeability

Corneal penetration studies have been conducted in unanesthetized albino rabbits using various organic compounds representing both polar and nonpolar species. In the presence of calcium chelating agents, polar compounds generally demonstrate an increase in corneal penetration. Evidence that this corneal effect is reversible is presented. Concomitant with an increase in both corneal and aqueous humor drug levels was a decrease in drug concentration in both iris and conjunctival tissues tentatively attributed to chelation effects on vascular permeability of these tissues. EDTA, a known calcium chelator, was shown to penetrate the cornea, conjunctiva, and iris/ciliary body from a topically applied dose. The implications of this observation pertain to both toxicity effects, when EDTA is incorporated into ocular drug products for stability purposes, and novel strategems for improving ocular bioavailability of topically applied drugs.     

Sodium activity in the aqueous humor and corneal stroma of the rabbit.

The present study examined the free sodium concentration of the aqueous humor and corneal stroma of both transparent and non-transparent corneas to assess the transendothelial activity gradient for sodium. In the transparent cornea of the adult rabbit, the sodium activity was higher in the aqueous humor than the stroma. This difference in sodium activity would cause water to diffuse down its concentration gradient from stroma to aqueous humor. In this way corneal transparency and the deturgesced state are maintained. Removal of the corneal endothelium in the adult rabbit produced an opaque swollen cornea. Under these conditions the sodium activity was higher in the stroma than the aqueous humor. However, an osmotic gradient was not produced by the Na+ activity gradient because the endothelium was not present to act as a semi-permeable membrane. The corneal endothelium was no longer present to establish and sustain the activity gradient for sodium that is necessary for corneal transparency in the mature rabbit. The transendothelial sodium activity gradient was also measured in 13-day-old rabbits. At this age, the cornea was not yet transparent, nevertheless the free sodium concentration of the aqueous humor was higher than that of the stroma, similar to the adult transparent cornea. This suggests that forces other than the establishment of the proper transendothelial sodium gradient are responsible for the lack of corneal transparency in the young rabbit.     

Concentrations of levofloxacin, ofloxacin, and ciprofloxacin in human corneal stromal tissue and aqueous humor after topical administration

OBJECTIVE: To evaluate the penetration of commercially available levofloxacin 0.5%, ofloxacin 0.3%, and ciprofloxacin 0.3% topical ophthalmic solutions in human corneal stromal and aqueous humor tissues. METHODS: A total of 67 patients scheduled to undergo penetrating keratoplasty for treatment of stromal scar or dystrophy, keratoconus, pellucid marginal degeneration, or endothelial disease were enrolled in this prospective, double-blind, 3-center study. To be considered for inclusion, patients had to have an intact corneal epithelium and minimal or no corneal edema (pachymetry < 650 microm). After informed consent was obtained, patients were randomized to receive 1 drop of levofloxacin 0.5%, ofloxacin 0.3%, or ciprofloxacin 0.3% topical ophthalmic solution at approximately 15 and 10 minutes before surgery. Approximately 0.1 mL of aqueous fluid was aspirated by paracentesis through the trephination wound at the onset of surgery, followed by excision of the affected cornea and removal of its epithelium. Specimens were stored frozen at -70 degrees C until assayed by high-performance liquid chromatography. RESULTS: All 3 fluoroquinolones were well tolerated. A total of 65 corneas and 59 aqueous fluid samples were obtained and assayed. The mean +/- standard deviation corneal concentrations of ciprofloxacin, ofloxacin, and levofloxacin following a 2-drop administration were 9.92 +/- 10.99 microg/g (n = 18), 10.77 +/- 5.90 microg/g (n = 23), and 18.23 +/- 20.51 microg/g (n = 24), respectively. Although corneal stromal levels were highest in the levofloxacin group, the high degree of interpatient variability prevented demonstration of statistically significant differences when compared with ofloxacin (P = 0.377). In contrast, levofloxacin concentrations were approximately twice as high as ciprofloxacin, and this difference reached statistical significance (P = 0.014). The corresponding aqueous humor concentrations of ciprofloxacin, ofloxacin, and levofloxacin were 0.135 +/- 0.231 microg/mL (n = 15), 0.135 +/- 0.111 microg/mL (n = 20), and 0.372 +/- 0.546 microg/mL (n = 24, P < 0.001 versus ciprofloxacin and ofloxacin). CONCLUSION: The topical administration of all 3 agents was well tolerated in patients undergoing penetrating keratoplasty. Two drops of levofloxacin 0.5% solution results in a 1.7- to 2.7-fold greater penetration into human corneal stromal and aqueous humor tissues than ofloxacin 0.3% or ciprofloxacin 0.3%. The mean intracorneal concentrations of all three agents following 2 drops exceeds the MIC90 for the majority of pathogens causing bacterial keratitis. Topical levofloxacin appears to offer pharmacokinetic and pharmacodynamic advantages over ofloxacin and ciprofloxacin in terms of enhanced transcorneal penetration; however, clinical comparative trials are needed to confirm these relative advantages.     

Intraocular availability of topically applied mycophenolate mofetil in rabbits.

The efficacy of mycophenolate mofetil (MMF), a prodrug of mycophenolic acid (MPA), in high risk keratoplasties and ocular immune-mediated diseases has been shown in recent years. As peroral administration of MMF can cause various side effects, topical application should be considered. This study investigates the intraocular availability of MMF and MPA in the rabbit eye. An eye drop solution (MMF-CD; 1% MMF/10% hydroxypropyl-beta-cyclodextrin (HP-beta-CD)) or a 1% aqueous suspension (MMF-SP) was instilled into the lower cul-de-sac of the right eye of each rabbit. Rabbits (each group: n = 4) were put down after 30, 60 and 240 min. Aqueous humor, vitreous, cornea, sclera, conjunctiva, iris-ciliary-body, and plasma were isolated. Several extraction procedures were performed in order to quantify the drug by HPLC. The aqueous humor concentration of the active metabolite MPA was 24 microg/mL after 30 min for both preparations. The ratio of the MPA concentrations after 30, 60, and 240 min was 1 : 2 : 0.07 for MMF-CD and 1 : 0.6 : 0.04 for MMF-SP, respectively. MPA levels in the cornea were 90.78 / 56.90 / 4.08 x 10(-6) microg/microg for MMF-CD, whereas MMF-SP resulted in MPA levels of 102.65 / 31.18 / 2.59 x 10(-6) microg/microg at the three time points. As a high concentration of the active drug MPA in cornea and aqueous humor is desired, e.g. following corneal transplantation, the MMF/HP-beta-CD formulation could be an useful topical treatment. Furthermore, the present study shows that MMF-CD is superior to MMF-SP by increasing intraocular availability.