Toxicity and pharmacokinetics of intrastromal injection of amphotericin B in a rabbit model

Efficacy of the Combined Intrastromal Injection of Voriconazole and Amphotericin B in Recalcitrant Fungal Keratitis

This study aims to report the efficacy of a combined intrastromal injection in optimizing the outcome of severe mycotic keratitis. Herein, we report a case series of 20 consecutive patients with positive fungal cultures not responding to topical antifungal treatment. Patients received cycles of intrastromal injections of voriconazole (50 µg/0.1 mL) and amphotericin B (2.5 µg/0.1 mL); all patients continued their topical antifungal therapy. The organisms isolated were Fusarium (n = 5), Aspergillus (n = 4), Candida (n = 4), Rhodotorula (n = 2), Penicillium (n = 2), Alternaria (n = 1), Bipolaris (n = 1), and Curvularia (n = 1). The size of the infiltrate varied from 6.5 to 1.5 mm. At presentation, the best corrected visual acuity (BCVA, namely, the best visual acuity achieved with glasses, if needed) was less than 20/400 in all patients, improving to better than 20/400 in eleven patients. Seven patients required surgical intervention; four of them underwent penetrating keratoplasty (PK) à chaud one month after the first intrastromal injection. Patients who underwent surgery achieved a BCVA of 20/40 or better. Combined intrastromal injections before therapeutic penetrating keratoplasty (TPK) effectively reduced ulcer size and graft diameter, preventing infection recurrence. Our results highlight the efficacy of combined intrastromal injections in optimizing outcomes for severe mycotic keratitis undergoing TPK.

Toxicity of simultaneous intrastromal and intracameral injection of voriconazole on corneal endothelium in a rabbit model

PURPOSE

To investigate the toxicity of repeated simultaneous intrastromal and intracameral injections of voriconazole in corneal endothelial cells in a rabbit model.

METHODS

Thirty-six eyes of 18 New Zealand white rabbits (six eyes per group) were divided into 6 groups according to the concentration of voriconazole (Group A, 0%; Group B, 0.05%; Group C, 0.1%; Group D, 0.25%; Group E, 0.5%; Group F, 1%). A combination of intrastromal and intracameral voriconazole injections were administrated to the eyes of each group three times on days 0, 3, and 7. Corneal clouding grades and central corneal thickness (CCT) were examined on days 0, 3, 7, 10, and 14. The endothelial cell counts (ECC) were measured on days 0 and 14. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were performed on day 14.

RESULTS

Group F (1%) showed more severe corneal clouding than the other groups (Groups A-E) from day 7 (p < 0.05, respectively). There were no significant differences in CCT and ECC among the six groups at any time point (p > 0.05, respectively). SEM revealed blurring of the cell border and loss of microvilli at concentrations ≥0.25% (Groups D-F). TEM revealed microstructural changes in endothelial cells at concentrations ≥0.1% (Groups C-F), and multiple vacuoles were observed at a concentration of 1% voriconazole (Group F).

CONCLUSIONS

Repeated simultaneous intrastromal and intracameral voriconazole injections at a concentration of 0.1% or higher induced microstructural endothelial damage in rabbit corneal endothelial cells.

Experimental Models for Fungal Keratitis: An Overview of Principles and Protocols

Fungal keratitis is a potentially blinding infection of the cornea that afflicts diverse patient populations worldwide. The development of better treatment options requires a more thorough understanding of both microbial and host determinants of pathology, and a spectrum of experimental models have been developed toward this end. In vivo (animal) models most accurately capture complex pathological outcomes, but protocols may be challenging to implement and vary widely across research groups. In vitro models allow for the molecular dissection of specific host cell–fungal interactions, but they do so without the appropriate environmental/structural context; ex vivo (corneal explant) models provide the benefits of intact corneal tissue, but they do not provide certain pathological features, such as inflammation. In this review, we endeavor to outline the key features of these experimental models as well as describe key technical variations that could impact study design and outcomes.

Corneal Pharmacokinetics of Voriconazole and Posaconazole following Intrastromal Injection and Posaconazole Eye Drops Instillation in Rats

Purpose/Aims: Infectious keratitis is a major cause of visual impairment and blindness worldwide. Common difficulties in treating fungal keratitis prompt new therapeutic possibilities. In this study, intrastromal voriconazole and posaconazole, and topical posaconazole were tested for their potential to obtain therapeutic cornea concentrations. Materials and Methods: Pharmacokinetics of triazole intracorneal/eye drop administration was studied in rats. Sixty-two rats were treated either by voriconazole or posaconazole. Twenty-nine and 33 rats received intrastromal injection of voriconazole solution (1 μl, 10 mg/ml) and posaconazole solution (1 μl, 18 mg/ml), respectively, administered under microscopic examination with a 32 gauge needle in the left cornea. Posaconazole (1.8% solution) eye drops were used. Cornea and plasma concentrations were determined using 2D HPLC separation and tandem MS, at 30 min, 3 h, 6 h, 24 h, 48 h, 72 h, and 144 h (6 days) post-intrastromal injection. The entire rat cornea was used for chromatography analyses. Results: In anesthetized rats, single intracorneal injection resulted, after 30 min, in respectively, >300 ng/mg and >260 ng/mg cornea concentrations, dropping to low levels within hours, while staying low in plasma. The effect of hourly posaconazole eye drops resulted in >10 ng/mg cornea concentration, which was maintained with instillations every 2 and then every 4 h. Conclusion: Our results show that there is little interest of intrastromal triazole administration due to the short duration of high cornea concentrations obtained after intracorneal injection. Posaconazole eye drops maintain therapeutic cornea concentrations in rats and could be used to treat severe infectious keratitis.

Recent advances in topical nano drug-delivery systems for the anterior ocular segment

Over the past decade, there has been a rise in the number of clinical cases of moderate to severe anterior segment ocular diseases. Conventional topical ophthalmic formulations have several limitations - to address which, novel drug-delivery systems are needed. Additionally, formidable physiological barriers limit ocular bioavailability through the topical route of application. During the last decade, various nano-scaled ocular drug-delivery strategies have been reported. Some of these exploratory, topical, noninvasive approaches have shown promise in improving penetration into the anterior segment tissues of the eye. In this article, we review the available literature with respect to the safety, efficiency and effectiveness of these nano systems.

Challenges in the Polyene- and Azole-Based Pharmacotherapy of Ocular Fungal Infections

Polyenes and azoles constitute 2 major drug classes in the antifungal armamentarium used to treat fungal infections of the eye such as fungal keratitis, endophthalmitis, conjunctivitis, and blepharitis. These classes of drugs have come to occupy an important niche in ophthalmic antifungal therapy due to their broad spectrum of activity against a variety of filamentous and yeast-like fungi. Natamycin suspension (Natacyn^®), a polyene antifungal drug, is currently the only US FDA-approved formulation for treating ophthalmic fungal infections, whereas the other polyene and azole antifungals such as amphotericin B, fluconazole, itraconazole, ketoconazole, miconazole, voriconazole, and posaconazole are routinely used off-label in the clinical setting. Despite potent antifungal activity, the clinical utility of these agents in ophthalmic infections has been challenged by their physicochemical properties, the unique ocular anatomy and physiology, selective antifungal activity, ocular and systemic toxicity, emergence of resistance and cross-resistance, and absence of reliable techniques for developing a robust in vitro-in vivo correlation. This review discusses the aforementioned challenges and the common approaches undertaken to circumnavigate the difficulties associated with the polyene- and azole-based pharmacotherapy of ophthalmic fungal infections.

Intracorneal Amphotericin B Injection in a Case of Indolent Candidal Keratitis

Ocular candidiasis is one of the opportunistic infection occurring in human body. Pathogenesis wise, Candida is very virulent and slow growing organism. We report a case of 76-year-old female with left eye candidal stromal abscess, not responding to topical and oral antifungal drugs. Patient was administered intrastromal amphotericin B injection in the affected eye. Four midstromal injections were given in the areas surrounding the corneal abscess. A total of approximately 0.05 mL of amphotericin B, 5 μg per 0.1 mL, was administered. Within next four weeks, the eye became completely quiet with healed epithelial defect and corneal scarring. Intracorneal injection of amphotericin B is a safe and effective treatment option for recurrent and recalcitrant fungal infections.

Combined intrastromal injection of amphotericin B and topical fluconazole in the treatment of resistant cases of keratomycosis: a retrospective study

Purpose

To evaluate the efficacy of combination therapy of a single intrastromal injection of amphotericin B and topical fluconazole in resistant cases of fungal keratitis, and also topical amphotericin B as monotherapy in terms of the duration of the recovery period and toxic drug effects.

Methods

This retrospective 2-year study reviewed 68 cases of unilateral fungal keratitis diagnosed by clinical features and positive laboratory culture results. Forty-one cases were resistant and did not respond to monotherapy with an antifungal agent. Thus, they were treated with a single intrastromal injection of amphotericin B in addition to topical fluconazole as combined antifungal therapy, representing group A. Twenty-seven cases were treated with topical amphotericin B as antifungal monotherapy, representing group B. Topical atropine 1% and different antibiotic eye drops were added to the antifungal agents in both groups. Follow-up of patient records was performed monitoring cure rate, duration of recovery period, and toxic drug effects such as pain, burning sensation, and corneal melting.

Results

The results revealed that group A, treated with combination therapy, showed recovery of 34 cases (82.9%) with a mean duration of 24±6.42 days, significantly different from group B which showed recovery of 16 cases (59.3%) with a mean duration of 39.66±13.6 days. Group A also showed less manifestation of drug toxicity than group B.

Conclusion

Combined intrastromal injection of amphotericin B and topical fluconazole can provide a good modality in the treatment of resistant cases of fungal keratitis, exhibiting highly potent antifungal effects, shorter recovery period, and reduced corneal toxicity.

Review of clinical and basic approaches of fungal keratitis

Fungal keratitis (FK) is a serious disease which can cause blindness. This review has current information about the pathogenesis, limitations of traditional diagnosis and therapeutic strategies, immune recognition and the diagnosis and therapy of FK. The information of this summary was reviewed regularly and updated as what we need in the diagnosis and therapy of FK nowadays.

A Combination of Intrastromal and Intracameral Injections of Amphotericin B in the Treatment of Severe Fungal Keratitis

Purpose. To evaluate the efficacy of a combination of intrastromal and intracameral injections of amphotericin B in the treatment of severe recalcitrant fungal keratitis. Methods. Patients with severe fungal keratitis who were resistant to conventional antifungal medical treatments and needed potential surgical intervention were recruited at the First Affiliated Hospital of Fujian Medical University between January 2012 and July 2013. The patients were treated with a combination of intrastromal and intracameral injections of amphotericin B (25 μg/mL and 50 μg/mL, resp.). Selectively repeated injections were performed as necessary. The efficacy, complications, and outcome were evaluated. Results. Nine patients (9 eyes) were involved in this study. All 9 cases responded favorably, and the clinical appearance of serious corneal damage and intraocular extension was resolved after the treatment. Four eyes required only 1 injection, and 5 eyes required repeated injections. Seven corneal ulcers healed with leucoma, and 2 healed with adherent leucoma. All of our cases had a marked increase in the anterior chamber reaction and pain immediately after the injection. There was no obvious clinical evidence of corneal or lenticular toxicity in any patient. Conclusions. A combination of intrastromal and intracameral injections of amphotericin B may be safe and effective for the treatment of severe fungal keratitis that is resistant to conventional therapy.