Ocular distribution of intravenously administered lipid formulations of amphotericin B in a rabbit model

Little is known about the ocular penetration of amphotericin B (AMB) and its lipid formulations, the current drug of choice in fungal endophthalmitis. The ocular distribution of AMB lipid complex (ABLC), liposomal AMB (L-AMB), and AMB deoxycholate (D-AMB) was studied in a rabbit model. D-AMB (1 mg/kg of body weight/day), ABLC (5 mg/kg/day), or L-AMB (5 mg/kg/day) was given intravenously to rabbits as a single dose or as repeated daily doses on 7 consecutive days after induction of unilateral uveitis by intravitreal injection of endotoxin. AMB concentrations in aqueous humor, vitreous humor, and plasma were determined by high-pressure liquid chromatography 16 h after administration of a single dose or 24 h after the last of seven doses. After single-dose administration, L-AMB achieved at least eightfold-higher AMB concentrations in the aqueous of inflamed eyes than ABLC or D-AMB (1.21 +/- 0.58 micro g/ml versus 0.14 +/- 0.04 and 0.11 +/- 0.09 micro g/ml, respectively). At that time point no drug was detectable in the vitreous. After 7 days of treatment, the concentration of AMB in the vitreous was higher after treatment with L-AMB (0.47 +/- 0.21 micro g/ml) than after treatment with ABLC (0.27 +/- 0.18 micro g/ml) and D-AMB (0.16 +/- 0.04 micro g/ml). Similarly, AMB concentration in the aqueous was higher after repeated doses of L-AMB (0.73 +/- 0.43 micro g/ml) than after repeated doses of ABLC (0.03 +/- 0.02 micro g/ml) or D-AMB (0.13 +/- 0.06 micro g/ml). No AMB was detected in noninflamed eyes. Following systemic administration, AMB distribution to the eye is inflammation dependent and occurs sequentially, first to the aqueous and then to the vitreous. Compared to D-AMB and ABLC, L-AMB reaches higher drug concentrations in both ocular compartments.     

Intraocular Penetration of Intravenous Micafungin in Inflamed Human Eyes

Eight eyes of 7 patients with fungal disease received intravenous injections of 150 to 300 mg micafungin, and samples of blood, cornea, retina-choroid, aqueous humor, and vitreous humor were collected. The micafungin levels in all collected samples exceeded the MICs; however, the levels in the vitreous and aqueous humors were lower. Our findings suggest that intravenous micafungin should be given in combination with intravitreal antifungal agents after vitrectomy in severe cases of intraocular fungal diseases.     

Pharmacokinetics and Safety of Intravitreal Caspofungin

Caspofungin exhibits potent antifungal activities against Candida and Aspergillus species. The elimination rate and retinal toxicity of caspofungin were determined in this study to assess its pharmacokinetics and safety in the treatment of fungal endophthalmitis. Intravitreal injections of 50 μg/0.1 ml of caspofungin were administered to rabbits. Levels of caspofungin in the vitreous and aqueous humors were determined using high-performance liquid chromatography (HPLC) at selected time intervals (10 min and 1, 2, 4, 8, 16, 24, and 48 h), and the half-lives were calculated. Eyes were intravitreally injected with caspofungin to obtain concentrations of 10 μg/ml, 50 μg/ml, 100 μg/ml, and 200 μg/ml. Electroretinograms were recorded 4 weeks after injections, and the injected eyes were examined histologically. The concentrations of intravitreal caspofungin at various time points exhibited an exponential decay with a half-life of 6.28 h. The mean vitreous concentration was 6.06 ± 1.76 μg/ml 1 h after intravitreal injection, and this declined to 0.47 ± 0.15 μg/ml at 24 h. The mean aqueous concentration showed undetectable levels at all time points. There were no statistical differences in scotopic a-wave and b-wave responses between control eyes and caspofungin-injected eyes. No focal necrosis or other abnormality in retinal histology was observed. Intravitreal caspofungin injection may be considered to be an alternative treatment for fungal endophthalmitis based on its antifungal activity, lower retinal toxicity, and lower elimination rate in the vitreous. More clinical data are needed to determine its potential role as primary therapy for fungal endophthalmitis.     

Effect of ocular compression on intraocular penetration of systemic ofloxacin

Intraocular levels of ofloxacin are documented after topical and systemic administration, but systemic administration of ofloxacin in ocular compression has not yet been studied. This study was undertaken to determine the intraocular penetration of systemic ofloxacin into aqueous and vitreous humor after the application of ocular compression in rabbit eyes. Ocular compression with the Honan balloon was applied for 30 min to the right eyes of 11 albino New Zealand white rabbits. After the application of ocular compression, 2 mg/mL of ofloxacin was administered intravenously. Samples from aqueous and vitreous humor were collected 30 min after infusion. Ofloxacin concentrations were determined through high-performance liquid chromatography. The mean aqueous level of ofloxacin was significantly higher in the compression group (2.40±1.00 gmg/mL) than in the no-compression group (1.61 ±1.06 μg/mL) (P < .05). The mean vitreous concentrations of ofloxacin were 0.70+-0.33 μg/mL and 0.50±0.18 μg/mL in the compression and no-compression groups, respectively. A significant difference was observed between vitreous levels of ofloxacin in the compression and nocompression groups (P < .05). Ocular compression enhanced the penetration of ofloxacin in both aqueous and vitreous humor. The drug level in the aqueous humor was sufficient for the minimum inhibitory concentration for 90% of isolates (MIC₉₀) to inhibit most microorganisms. Although the mean vitreous ofloxacin concentration was increased by previous ocular compression, it was not sufficiently above the MIC₉₀ for most ocular pathogens that caused endophthalmitis.     

Measurement of antifungal drug levels in cerebrospinal fluid for cryptococcal meningoencephalitis

We report a rare case of cryptococcal meningoencephalitis in which antifungal therapy was monitored by measuring the cerebrospinal fluid (CSF) levels of the antifungal drugs. A 78-year-old man with diabetes mellitus being treated with oral agents. He had no history of human immunodeficiency virus infection. The patient showed abnormal behavior and fever (>38°C) on November 20, 2009, and was admitted for disturbance of consciousness on November 24. CSF examination showed an increased cell count, and a yeast-like fungus, suggesting cryptococcal meningoencephalitis, was observed by India ink staining. Initial treatment was liposomal amphotericin B (L-AMB) plus flucytosine. Cryptococcus neoformans was isolated by CSF culture on day 2. MIC was 0.25 μg/ml for amphotericin B (AMPH-B), 4 μg/ml for flucytosine, 4 μg/ml for fluconazole (FLCZ), and 0.03 μg/ml for voriconazole (VRCZ). Despite treatment, his disturbance of consciousness persisted. The CSF level of AMPH-B was ≤0.05 μg/ml on day 8. Therefore, L-AMB was switched to fosfluconazole. The CSF level of FLCZ was sufficient (22.6 μg/ml) on day 25, but there was a decrease in glucose and the fungus could still be detected in CSF smears. Consequently, FLCZ was switched to VRCZ. On day 47, CSF level of VRCZ was 1.97 μg/ml, exceeding its MIC, so treatment was continued. On day 77, the patient was generally lucid, and CSF smears did not detect any fungi. The patient was then transferred for rehabilitation. On day 84, voriconazole was discontinued, with no evidence of fungal recurrence.     

Voriconazole concentration in human aqueous humor and plasma during topical or combined topical and systemic administration for fungal keratitis

Voriconazole (VRC) is an antifungal drug that effectively treats keratitis caused by yeasts and molds when administered orally. We retrospectively evaluated clinical outcomes and plasma and aqueous humor drug concentrations in five patients with fungal keratitis and one patient with posttraumatic endophthalmitis who were treated with VRC. VRC was administered either topically (1% eye drops every hour) or orally (400 mg twice a day). Plasma and aqueous humor samples from affected eyes were taken 12 h after oral administration or 1 h after eye drop application. The drug concentration was measured by liquid chromatography with UV or mass spectrometric detection. All six patients responded well to VRC treatment. The VRC concentration ranged from 2.93 to 3.40 mg/liter in the aqueous humor and from 3.20 to 4.20 mg/liter in the plasma after combined oral and topical treatment. Topical administration alone resulted in highly variable trough VRC concentrations of 0.61 to 3.30 mg/liter in the aqueous humor. VRC concentrations were above the MIC for Candida albicans Aspergillus fumigatus and clinical improvement was seen in all four patients with C. albicans and A. fumigatus keratitis. Combined orally and topically administered VRC resulted in aqueous humor drug concentrations of > or =2.93 mg/liter, which is above the VRC MIC for most fungi. Topical VRC treatment resulted in an aqueous humor drug concentration >0.61 mg/liter, which is above the MIC for most Candida species. The results from this small series of patients suggest that both topical and combined systemic and topical VRC therapy can be effective in treating fungal keratitis. Furthermore, the data provide preliminary support for initiation of VRC treatment with a combined topical and systemic administration until the causative fungus and its MIC are identified.     

Poor penetration of cefcapene into aqueous humor after oral administration of cefcapene pivoxil to patients undergoing cataract surgery

ObjectivesStudies on the penetration of orally administered cephalosporins to the aqueous humor are scarce. Therefore, in this study, we determined the concentration of cefcapene, a third-generation cephalosporin administrated orally as pivalate ester (cefcapene pivoxil), in the aqueous humor of patients undergoing cataract surgery to assess its potential for preventing postoperative endophthalmitis.MethodsForty-four patients were administered a single dose of 100 mg cefcapene pivoxil preoperatively. Blood and aqueous humor samples were obtained at the time of surgery, and cefcapene concentrations were measured using ultra-performance liquid chromatography with tandem mass spectrometric detection.ResultsThe samples were obtained from 41 eyes of 39 patients (two patients underwent surgery in both eyes). The median cefcapene concentrations in the aqueous humor after 1–2 h, 2–3 h, and later than 3 h were 8.3, 18.4, and 23.7 ng/mL, respectively. The median cefcapene concentrations in serum after 1–2 h, 2–3 h, and later than 3 h were 198.5, 287.2, and 170.3 ng/mL, respectively. Aqueous humor penetration of cefcapene after 1–2 h, 2–3 h, and later than 3 h was 4.1, 7.9, and 13.5% respectively.ConclusionsAqueous humor penetration of orally-administered cefcapene pivoxil in patients undergoing cataract surgery was poor. Therefore, cefcapene pivoxil was unlikely to be effective for preventing endophthalmitis after cataract surgery.     

Comparative study of the efficacy of liposomal amphotericin B and amphotericin B deoxycholate against six species of Zygomycetes in a murine lethal infection model

The objective of this study was to investigate the efficacy of liposomal amphotericin B (L-AMB) at a clinical dose (3 mg/kg) against six species (5 genera) of Zygomycetes in a murine lethal infection model, and to compare findings with those for deoxycholate amphotericin B (D-AMB). The correlation between in-vitro activity and in-vivo efficacy of L-AMB was also investigated. Cyclophosphamide-treated mice were inoculated intravenously with conidial suspensions. Four hours or 1 day after inoculation, a single dose of L-AMB or D-AMB was administered intravenously. The number of mice that survived for 14 days was recorded. L-AMB at a dose of at least ≥1 mg/kg significantly prolonged the survival time of infected mice compared with the control group. The ED₅₀ of L-AMB was nearly equivalent to that of D-AMB, except for the treatment initiated on day 1 in the Rhizopus oryzae model. At the maximum tolerated dose (MTD) of each agent, survival percentages with L-AMB (10 mg/kg) were equal to or higher than those with D-AMB (1 mg/kg). The ED₅₀ of L-AMB decreased as the MIC against the infecting strain decreased. In conclusion, L-AMB was effective at a clinical dosage, and at the MTD the efficacy of L-AMB was equal or superior to that of D-AMB in a murine model of disseminated zygomycosis. The in-vivo activity of L-AMB was correlated with its in-vitro activity.     

Pharmacokinetics and Pharmacodynamics of Anidulafungin for Experimental Candida Endophthalmitis: Insights into the Utility of Echinocandins for Treatment of a Potentially Sight-Threatening Infection

Candida chorioretinitis and endophthalmitis are relatively common manifestations of disseminated candidiasis. Anidulafungin is increasingly used for the treatment of disseminated candidiasis, but its efficacy for Candida endophthalmitis is not known. A nonneutropenic model of hematogenous Candida endophthalmitis was used. Anidulafungin at 5, 10, and 20 mg/kg was initiated at 48 h postinoculation. The fungal densities in the kidney and vitreous humor were determined. Anidulafungin concentrations in the plasma and vitreous humor were measured using high-performance liquid chromatography (HPLC). A pharmacokinetic-pharmacodynamic model was used to link anidulafungin concentrations with the observed antifungal effect. The area under the concentration-time curve (AUC) associated with stasis was determined in the both the kidney and the vitreous humor. The results were bridged to humans to identify likely dosages that are associated with significant antifungal activity within the eye. Inoculation of Candida albicans resulted in logarithmic growth in both the vitreous humor and the kidney. The pharmacokinetics of anidulafungin were linear. There was dose-dependent penetration of the anidulafungin into the vitreous humor. The exposure-response relationships in the kidney and vitreous were completely discordant. AUCs of 270 and 100 were required for stasis in the eye and kidney, respectively. The currently licensed regimen results in an AUC for an average patient that is associated with stasis in the kidney but minimal antifungal activity in the eye. We conclude that anidulafungin penetrates the eye in a dose-dependent manner and that dosages higher than those currently licensed are required to achieve significant antifungal activity in the eye.     

Fleroxacin pharmacokinetics in aqueous and vitreous humors determined by using complete concentration-time data from individual rabbits.

Although composite data from separate subjects can be used to generate single-subject estimates, intersubject variation precludes rigorous ocular pharmacokinetic analysis. Therefore, a rabbit model in which sequential aqueous and vitreous humor samples were obtained following the administration of the quinolone fleroxacin was developed. Mean data from individual animals were used for pharmacokinetic analysis. Following direct intravitreal or systemic drug administration, sequential paracenteses did not alter pharmacokinetic constants or ocular penetration and were not associated with an increase in ocular protein; contamination of vitreous humor with blood was minimal (less than 0.1%). Following direct injection or intravenous administration, vitreous humor concentration-time data were best described by one- and two-compartment models, respectively. The maximum concentration and the penetration into the aqueous and vitreous humors were 1.54 and 0.5 micrograms/ml and 27 and 10%, respectively. Elimination rates from aqueous and vitreous humors and serum were similar following parenteral drug administration. Drug elimination following direct injection was rapid, and the elimination rate from the vitreous humor was not prolonged by the coadministration of probenecid. Our animal model provides a new approach to the rigorous examination of the ocular pharmacokinetics of quinolone antimicrobial agents in the eye.     

Efficacy of early administration of liposomal amphotericin B in patients with septic shock: A nationwide observational study

IntroductionLiposomal amphotericin B (L-AMB), a broad spectrum anti-fungicidal drug, is often administered to treat invasive fungal infections (IFIs). However, the most suitable time to initiate treatment in septic shock patients with IFI is unknown.MethodsPatients with septic shock treated with L-AMB were identified from the Japanese Diagnosis Procedure Combination national database and were stratified according to L-AMB treatment initiation either at septic shock onset (early L-AMB group) or after the onset (delayed L-AMB group) to determine their survival rates following septic shock onset and the shock cessation period.ResultsWe identified 141 patients administered L-AMB on the day of or after septic shock onset: 60 patients received early treatment, whereas 81 patients received delayed treatment. Survival rates after septic shock onset were higher in the early L-AMB group than in the delayed L-AMB group (4 weeks: 68.4% vs 57.9%, P = 0.197; 6 weeks: 62.2% vs 44.5%, P = 0.061; 12 weeks: 43.4% vs 35.0%, P = 0.168, respectively). The septic shock cessation period was shorter in the early L-AMB group than in the delayed L-AMB group (7.0 ± 7.0 days vs 16.5 ± 15.4 days, P < 0.001), with a significant difference confirmed after adjusting for confounding factors with propensity score matching (7.1 ± 7.2 days vs 16.7 ± 14.0 days, P = 0.001).ConclusionEarly L-AMB administration at septic shock onset may be associated with early shock cessation.     

Modeling approach to characterize intraocular doripenem pharmacokinetics after intravenous administration to rabbits, with tentative extrapolation to humans

The aim of this study was to determine the penetration of doripenem administered intravenously into the rabbit aqueous and vitreous humors. Nineteen New Zealand White rabbits received a 20-mg dose of doripenem intravenously over 60 min. Specimens of aqueous humor, vitreous humor, and blood were obtained 30 min (n = 5), 1 h (n = 5), 2 h (n = 5), and 3 h (n = 4) after the beginning of the infusion and analyzed by high-performance liquid chromatography (HPLC). A pharmacokinetic (PK) model was developed to fit the experimental data. Doripenem concentrations in aqueous humor were lower than those in plasma ultrafiltrates at all sampling times, with an average aqueous humor-to-plasma ultrafiltrate area under the concentration-time curve ratio estimated as 8.3%. A pharmacokinetic model with peripheral elimination described the data adequately and was tentatively used to predict concentration-versus-time profiles and pharmacokinetic-pharmacodynamic (PK-PD) target attainment in patients under various dosing regimens. In conclusion, systematically administered doripenem does not seem to be a promising approach for the treatment of intraocular infections, especially since it could not be detected in the vitreous humor. However, this study has provided an opportunity to develop a new PK modeling approach to characterize the intraocular distribution of doripenem administered intravenously to rabbits, with tentative extrapolation to humans.     

Efficacy of aerosolized liposomal amphotericin B against murine invasive pulmonary mucormycosis

Invasive pulmonary mucormycosis is a life-threatening fungal infection encountered in immunocompromised patients. An intravenous high-dose lipid formulation of amphotericin B, such as liposomal amphotericin B (L-AMB), is the recommended treatment. The efficacy of inhaled L-AMB against mucormycosis has not been evaluated.We evaluated the efficacy of inhaled aerosolized L-AMB in murine invasive pulmonary mucormycosis. ICR female mice were immunosuppressed with cortisone acetate and cyclophosphamide and challenged on day 0 with 1 × 10⁶ conidia of Rhizopus oryzae (TIMM 1327) intratracheally. Infected mice were assigned to one of the following 3 treatment groups: (i) control, (ii) treatment only (aerosolized L-AMB from day 1–5 after challenge), and (iii) prophylaxis followed by treatment (aerosolized L-AMB from day −2 to 5 before and after challenge). Survival was monitored until 12 days after challenge. For fungal-burden and histopathological examination, mice were sacrificed 4 h after treatment on day 3. Numbers of colony-forming units per lung were calculated. To study the distribution of AMB after inhalation of L-AMB, immunohistochemical studies using AMB antibody were performed.Aerosolized L-AMB significantly improved survival rate and decreased fungal burden compared with control group, and histopathology findings were superior to those of control group. However, no significant differences were detected between the treatment-only and prophylaxis followed by treatment groups. Immunohistochemical analysis showed that L-AMB was promptly distributed in lung tissue after inhalation therapy.Aerosolized L-AMB showed modest efficacy against R. oryzae infection in mice treated after fungal challenge. Prophylaxis with aerosolized L-AMB was not effective in this animal model.     

Ocular distribution of intravenously administered micafungin in rabbits

The ocular distribution of micafungin (MCFG), which has antifungal activity against Candida and Aspergillus species, was followed after the systemic administration of MCFG in rabbits. After MCFG (10 mg/kg) plus fluconazole (FLCZ; 10 mg/kg) was administered intravenously, the rabbits were killed, and MCFG and FLCZ concentrations in retina-choroid, vitreous humor, and plasma were determined by high performance liquid chromatography or liquid chromatography/mass spectrometry. The mean concentrations of MCFG in the retina-choroid at 0.25, 0.75, 4, 8, and 24 h after administration were 20.18, 15.97, 13.19, 6.27, and 0.75 microg/g, respectively, and were comparable with the MCFG plasma concentrations. The MCFG concentrations in retina-choroid and plasma exceeded the minimal antifungal inhibitory concentrations for endophthalmitis, although MCFG was not detected in the vitreous humor. These results suggest that the intravenous administration of MCFG is an effective treatment for endogenous fungal endophthalmitis when the causative fungus is localized in the retina and choroid.     

Discrepancy of in-vitro data and clinical efficacy of micafungin against Candida tropicalis endophthalmitis

We report findings for a 74-year-old woman with Candida tropicalis endophthalmitis for whom an increase in β-d-glucan level and worsening of endophthalmitis were observed after intravenous injection of micafungin, an echinocandin antifungal agent. Endogenous endophthalmitis caused by C. tropicalis developed in both eyes. On the basis of her surgical history, laboratory data, and lesions, tentative diagnosis of fungal endophthalmitis was made. She was then treated with fluconazole and itraconazole, but the β-d-glucan level did not decrease, and there was no improvement of the endophthalmitis. The fluconazole was discontinued and replaced by micafungin. Unexpectedly, the level of β-d-glucan increased and endophthalmitis did not improve. The micafungin was immediately stopped and replaced by intravenous fluconazole with amphotericin B syrup, but the itraconazole was continued. Marked resolution of the vitreous inflammation was observed in both eyes, and the serum β-d-glucan level was reduced. Because active macular infiltrates were observed in the right eye, vitrectomy was performed. The micafungin minimum inhibitory concentration against the C. tropicalis strain isolated from our patient was 0.03 μg/ml. This paradoxical effect of micafungin should be remembered, and β-d-glucan level should be frequently monitored after intravenous injection of micafungin.     

Comparison of fluconazole and amphotericin B for treatment of disseminated candidiasis and endophthalmitis in rabbits.

We compared the efficacy of intravenous fluconazole (80 mg/kg of body weight per day) with that of amphotericin B (1 mg/kg/day) for the long-term treatment of endophthalmitis in rabbits with disseminated candidiasis. After 17 days of therapy, fluconazole decreased the fungal colony counts of the choroid-retinas significantly more than did the saline control (P less than 0.05); however, after 24 days of fluconazole therapy, this treatment effect was lost and fluconazole was no more effective than saline. In contrast, treatment for 24 days with amphotericin B reduced the vitreous and choroid-retina fungal colony counts significantly more than either fluconazole or saline (P less than 0.05 for both treatment groups). After 17 days of therapy, indirect ophthalmoscopy revealed less severe eye involvement in both antifungal treatment groups than in saline controls; however, this difference reached statistical significance only for the amphotericin B-treated rabbits (P less than 0.05). Also, there was a trend towards worsening eye lesions, as seen by indirect ophthalmoscopy, in the fluconazole-treated rabbits after 24 days of therapy, which roughly paralleled the quantitative culture results. Despite the presence of negative choroid-retina cultures, some rabbits in all treatment groups had persistently visible eye lesions, indicating that ophthalmoscopic resolution of Candida endophthalmitis may lag behind lesion sterilization. Amphotericin B was superior to fluconazole in the treatment of Candida endophthalmitis in this model.     

Nephrotoxicity and other adverse events among inpatients receiving liposomal amphotericin B or amphotericin B lipid complex

Nephrotoxicity evaluations between liposomal amphotericin B (L-AMB) and amphotericin B lipid complex (ABLC) have provided mixed results. This retrospective study used an electronic medical record database of hospitalized patients with invasive fungal infections treated with either L-AMB or ABLC. Patients had renal insufficiency, clinical condition suggesting intolerance to amphotericin B deoxycholate (CAB), or recent CAB exposure. Baseline SCr, exposure to other nephrotoxic agents, and total amphotericin B exposure were similar between the groups. In 105 patients administered L-AMB, 10.6% had nephrotoxicity versus 22.6% of 222 patients administered ABLC (P = 0.020). A logistic regression model found ABLC patients had 3.48 higher odds (95% CI 1.05–11.52) than L-AMB of developing nephrotoxicity. Infusion reactions were more prevalent with ABLC (23.9% versus 9.5%, P = 0.002) as was hypomagnesemia (44.3% versus 28.1%, P = 0.033). This study demonstrated that L-AMB is associated with less nephrotoxicity, infusion reactions and hypomagnesemia than ABLC in patients at increased risk of nephrotoxicity.     

Topical voriconazole as a novel treatment for fungal keratitis

Paecilomyces lilacinus is a fungal pathogen which is generally resistant to amphotericin B and certain other antifungals and is an uncommon cause of devastating fungal keratitis. In the present studies, we evaluated topical voriconazole as therapy for P. lilacinus keratitis in rabbits. Thirty eyes of 15 rabbits were studied. In five animals, the uninfected left eye was treated twice daily with voriconazole (drug control, uninfected eye). In these same animals, the right eye was infected with P. lilacinus but not treated with voriconazole (infection control eye). By day 5, the infection controls had lesions of >2.4 mm in diameter, with conjunctivitis and severe hypopyon, and were sacrificed. In the other 10 rabbits (voriconazole treatment), the right eyes were infected with P. lilacinus and treated with voriconazole beginning on day 3 after infection. Voriconazole therapy caused lesions to decrease during 8 days of therapy, after which rabbits were sacrificed (11 days postinfection). Hyphal masses were present in the control infected eyes and absent in treated infected eyes. Voriconazole was detected in all tissues of treated eyes. Topical voriconazole is effective treatment for P. lilacinus experimental keratitis, and it penetrates more deeply than the corneal tissue.     

Pharmacokinetics of Intracameral Voriconazole Injection

Elimination of voriconazole after intracameral injection exhibited an exponential decay with a half-life of 22 min. Voriconazole levels in the vitreous humor were below the detectable limit. The aqueous concentrations achieved with a 25-μg dose during the first 2 h were greater than the previously reported MICs of organisms most involved in fungal endophthalmitis. A rapid decline in intracameral concentration suggests that frequent supplementation of intracameral voriconazole may be required in clinical settings.Exogenous fungal endophthalmitis, a potentially devastating infection, results from intraocular surgery, ocular trauma, and contiguous spread from fungal keratitis. Intraocular injection is considered to be the mainstay of treatment for fungal endophthalmitis, and amphotericin B was the only antifungal agent approved for intraocular injection in the past. Voriconazole is a broad-spectrum antifungal agent, which inhibits the fungal enzyme cytochrome P450 demethylase. Clinically, voriconazole has been shown to be an effective form of primary therapy in the treatment of invasive aspergillosis and is an effective form of salvage therapy for refractory infections caused by Fusarium species (9). In experimental studies, voriconazole has been shown to be less toxic to the retina than amphotericin B and to exhibit an exponential decay with a half-life of 2.5 h in rabbit vitreous humors and a very low aqueous concentration, below the therapeutic levels for fungal species (2, 11). Therefore, intracameral voriconazole injection is considered to be the most direct and effective method for achieving a higher aqueous concentration.Voriconazole (VFEND; Pfizer, Inc., New York, NY) was obtained in pure powder form and reconstituted in sterile water to obtain a concentration of 25 μg/25 μl. Twenty-three New Zealand White rabbits were used in the study. All care and handling of rabbits were performed in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research, with the approval of the Institutional Authority for Laboratory Animal Care at Taichung Veterans General Hospital. Treatment was administered using a 30-gauge needle attached to a 100-μl microsyringe. An anterior chamber injection of 25 μg voriconazole in 25 μl sterilized distilled water was performed at 11 o''clock, and then the needle penetrated out of the cornea at 1 o''clock. Aqueous humor samples were obtained using a 27-gauge needle attached to a regular insulin syringe. Sampling was performed at set time intervals (15, 30, 45, 60, 90, 120, 150, 180, and 240 min) after injection and before enucleation of the eyes. Four to six eyes per time interval up to 240 min were enucleated on the same day. The entire vitreous humor was isolated according to the technique described by Abel and Boyle (1). Analysis of the samples was performed with high-performance liquid chromatography in a masked fashion. The procedures of voriconazole extraction from aqueous and vitreous humors were as described in a previous study (11).The mean voriconazole levels measured for vitreous and aqueous humors at all sampling times are listed in Table ​Table1.1. An exponential decay model was used to fit the data, and a least-square regression analysis was performed. The equations used for the calibration curve were as follows: y = 45.349e^−2.0581x and R² = 0.9813. The elimination rate constant (K) was derived from the slope of the line of the log concentration versus time, and the elimination half-life was calculated by 0.693/K. The aqueous humor voriconazole concentration showed an exponential decay with a half-life of 22 min. The vitreous concentration was below the detection limit at each time point.

TABLE 1.

Measured aqueous and vitreous levels of voriconazole at different time intervals after intracameral injection of 25 μg/25 μl in rabbits

The intraocular dynamics of vancomycin hydrochloride ophthalmic ointment (TN-011) in rabbits

The intraocular dynamics of 1% vancomycin hydrochloride (VCM) ophthalmic ointment (TN-011) in rabbits was investigated. The animals used in the study were 42 pigmented rabbits with normal eyes (normal group) and 17 pigmented rabbits with Bacillus subtilis-infected eyes (BS group). The infection in the BS group was induced by a method previously established by the authors. Fifty milligrams of a 1% VCM ophthalmic ointment was administered into the cul-de-sacs of the animals' eyes unilaterally in both groups. Serum, bulbar conjunctiva (only from the normal group), cornea, iris-ciliary body, and vitreous were collected 15, 30, 60, 120, and 240 min after the drug administration as samples. Drug concentration was measured by the bioassay method. In the normal group, VCM in the bulbar conjunctiva reached a maximum concentration (98.98 ± 46.48 μg/g) at 30 min, and decreased to a level below the detection limit at 240 min. The maximum concentration of VCM in the cornea (12.04 ± 4.73 μg/g) was observed at 30 min. VCM was not detected in the aqueous humour, iris-ciliary body, vitreous, or serum in the normal group at any point. In the BS group, the maximum concentration of VCM was 25.60 ± 11.01 μg/g in the cornea 15 min after drug administration, and 5.18 ± 2.60 μg/ml in the aqueous humour at 30 min. VCM in the aqueous humor could be detected (0.37 ± 0.19 μg/ml) even after 240 min. VCM was not detected in the iris-ciliary body, vitreous, or serum at any point. The intraocular dynamics of 1% VCM ophthalmic ointment (TN-011) revealed that VCM reached the estimated effective concentrations in the aqueous humour as well as extraocular tissues of Bacillus subtilis-infected rabbit eyes. Received: August 8, 2002 / Accepted: November 18, 2002 Acknowledgments. The authors thank Toa Pharmaceutical Co., Ltd. for providing us with the VCM ophthalmic ointment, TN-011.