Oral fluconazole therapy for keratomycosis

Lipo-PEG nano-ocular formulation successfully encapsulates hydrophilic fluconazole and traverses corneal and non-corneal path to reach posterior eye segment

The present study describes a special lipid-polyethylene glycol matrix solid lipid nanoparticles (SLNs; 138 nm; -2.07 mV) for ocular delivery. Success of this matrix to encapsulate (entrapment efficiency - 62.09%) a hydrophilic drug, fluconazole (FCZ-SLNs), with no burst release (67% release in 24 h) usually observed with most water-soluble drugs, is described presently. The system showed 164.64% higher flux than the marketed drops (Zocon^®) through porcine cornea. Encapsulation within SLNs and slow release did not compromise efficacy of FCZ-SLNs. Latter showed in vitro and in vivo antifungal effects, including antibiofilm effects comparable to free FCZ solution. Developed system was safe and stable (even to sterilisation by autoclaving); and showed optimal viscosity, refractive index and osmotic pressure. These SLNs could reach up to retina following application as drops. The mechanism of transport via corneal and non-corneal transcellular pathways is described by fluorescent and TEM images of mice eye cross sections. Particles streamed through the vitreous, crossed inner limiting membrane and reached the outer retinal layers.

Fungal keratitis

CLINICAL QUESTION

What is the most appropriate management of fungal keratitis?

RESULTS

Traditionally, topical Natamycin is the most commonly used medication for filamentous fungi while Amphotericin B is most commonly used for yeast. Voriconazole is rapidly becoming the drug of choice for all fungal keratitis because of its wide spectrum of coverage and increased penetration into the cornea.

IMPLEMENTATION

Repeated debridement of the ulcer is recommended for the penetration of topical medications. While small, peripheral ulcers may be treated in the community, larger or central ulcers, especially if associated with signs suggestive of anterior chamber penetration should be referred to a tertiary center. Prolonged therapy for approximately four weeks is usually necessary.

Current perspectives on ophthalmic mycoses

Fungi may infect the cornea, orbit and other ocular structures. Species of Fusarium, Aspergillus, Candida, dematiaceous fungi, and Scedosporium predominate. Diagnosis is aided by recognition of typical clinical features and by direct microscopic detection of fungi in scrapes, biopsy specimens, and other samples. Culture confirms the diagnosis. Histopathological, immunohistochemical, or DNA-based tests may also be needed. Pathogenesis involves agent (invasiveness, toxigenicity) and host factors. Specific antifungal therapy is instituted as soon as the diagnosis is made. Amphotericin B by various routes is the mainstay of treatment for life-threatening and severe ophthalmic mycoses. Topical natamycin is usually the first choice for filamentous fungal keratitis, and topical amphotericin B is the first choice for yeast keratitis. Increasingly, the triazoles itraconazole and fluconazole are being evaluated as therapeutic options in ophthalmic mycoses. Medical therapy alone does not usually suffice for invasive fungal orbital infections, scleritis, and keratitis due to Fusarium spp., Lasiodiplodia theobromae, and Pythium insidiosum. Surgical debridement is essential in orbital infections, while various surgical procedures may be required for other infections not responding to medical therapy. Corticosteroids are contraindicated in most ophthalmic mycoses; therefore, other methods are being sought to control inflammatory tissue damage. Fungal infections following ophthalmic surgical procedures, in patients with AIDS, and due to use of various ocular biomaterials are unique subsets of ophthalmic mycoses. Future research needs to focus on the development of rapid, species-specific diagnostic aids, broad-spectrum fungicidal compounds that are active by various routes, and therapeutic modalities which curtail the harmful effects of fungus- and host tissue-derived factors.

Therapeutic penetrating keratoplasty in severe fungal keratitis using cryopreserved donor corneas

AIMS

To investigate whether cryopreserved donor cornea could be used for therapeutic penetrating keratoplasty (PKP) to eradicate the infection, obviate complications, and preserve anatomical integrity in severe fungal keratitis.

METHODS

In this retrospective, consecutive case series, 45 eyes of 45 patients with severe fungal keratitis, which exhibited anterior chamber collapse, corneal perforation, and/or large suppurative corneal infiltrate, received therapeutic PKP after removal of the infected corneal tissue, irrigation of the anterior chamber by 0.2% fluconazole solution, iris dissection of fibrinoid membrane, and iridectomy and therapeutic PKP using corneas cryopreserved at -20 degrees C.

RESULTS

Among 45 eyes, 39 eyes (86.7%) were successfully eradicated the fungal infection without recurrence and maintained their anatomical integrity without any complication. Four of 45 eyes (8.9%) showed postoperative rise of intraocular pressure, of which three were controlled with subsequent antiglaucoma surgeries, whereas one eye needed additional antiglaucoma medications. Two of 45 eyes (4.4%) were enucleated because of uncontrollable fungal infection and secondary retinal detachment, respectively. 23 eyes received subsequent optical PKP and, among them, 21 maintained clear corneal grafts and two suffered from graft failure due to allograft rejections.

CONCLUSION

Cryopreserved donor corneas are effective substitutes in therapeutic PKP to control severe fungal corneal infection and preserve the global integrity, and may offer additional advantages over conventional PKP in reducing allograft rejection, eradicating fungal infection during the postoperative period, and improving the success of optical PKP for visual rehabilitation.

Comparison of efficacy of topical and oral fluconazole treatment in experimental Aspergillus keratitis

PURPOSE

To investigate the therapeutic role of topical and oral fluconazole treatment using a rabbit model of Aspergillus fumigatus keratitis.

METHODS

Aspergillus fumigatus spores were injected into the corneal stroma of the right eye of 20 rabbits. Forty-eight hours later the rabbits were randomly divided into three groups. Group 1 rabbits (six) were treated with topical fluconazole (2 mg/ml, eight times daily), group 2 rabbits (seven) received oral fluconazole (37.5 mg/kg bid), and group 3 rabbits (seven) were untreated controls. The eyes were examined and photographed with a slit-lamp 2, 6, 10, 16, and 20 days after inoculation and an observer graded the corneas in a masked fashion. Corneal cultures were taken on days 2, 14, and 20 for fungus growth.

RESULTS

At the beginning of treatment, the slit-lamp scores did not differ among three groups. However, on days 6, 10, 16, and 20 the treated groups had statistically significant lower scores compared to the untreated controls. No significant difference was observed between topical and oral treated groups at any examination point. All cultures were positive on day 2, but on days 16 and 20, there were significantly lower positive fungal cultures in both treatment groups compared to the control (p < 0.01, chi square test).

CONCLUSION

Our study showed that both topical and oral fluconazole were effective in lessening the severity of fungal keratitis in a rabbit model and should be considered effective treatment alternatives in the therapy of Aspergillus fumigatus keratitis.

Advances in the management of keratomycosis and Acanthamoeba keratitis

PURPOSE

In the late 1960s, the management of fungal keratitis was a serious unresolved problem. Little was known of the epidemiology of the disease, and there were no antifungal agents formulated for use in the eye.

METHODS

A thorough review of the literature was done back to 1969 on clinical reports and experimental studies for keratomycosis and Acanthamoeba keratitis.

RESULTS

Since 1969, through basic and clinical research, the epidemiology of the disease worldwide is better understood. One new topical antifungal agent, natamycin, with efficacy against filamentous fungi has been developed and the pharmacokinetics of topically applied antifungal drops have been explored. Progress has been slow but the prognosis for keratomycosis has immeasurably improved over the period. Acanthamoeba was first recognized as an ocular pathogen in 1973 and was the cause of an epidemic in the 1980s caused by contaminated contact lens, although other risk factors were also identified. At the onset of the epidemic, there was no known treatment. but as a result of intense research efforts, within a few years a well-defined therapeutic approach had been developed that had a significant impact on the prognosis for this initially devastating infection. For both infections, the role of corticosteroids for controlling the inflammation remains controversial, but the place for keratoplasty is now well defined.

CONCLUSIONS

Although there has been steady progress in the management of both infections, continued research is the way to define more effective medical and surgical therapy.

Medical management of Beauveria bassiana keratitis

PURPOSE

To describe a case of Beauveria bassiana keratitis and to discuss the management of this rare condition.

METHODS

An 82-year-old woman underwent surgical repair of a graft wound dehiscence. Seven months later, shortly after the removal of sutures, the patient developed a fungal keratitis. B. bassiana was identified as the infecting organism. The patient was treated with topical natamycin and oral fluconazole.

RESULTS

Following antifungal therapy, the corneal ulcer was eradicated, but the patient underwent repeat penetrating keratoplasty for decreased vision due to corneal edema. The graft remains clear and visual acuity is substantially improved.

CONCLUSION

The medical management of B. bassiana keratitis has previously been unsuccessful. The use of topical natamycin combined with oral fluconazole in the management of this case is discussed.

Fungal corneal ulcers of onion harvesters in southern Taiwan

Fungal corneal ulcers related to agriculture has been reported throughout the world, especially in tropical areas. Most of them were sporadic and had histories of ocular trauma or use of topical corticosteroids and topical antibiotics. Five onion harvesters had fungal corneal ulcers during the same harvest period in Southern Taiwan. The authors think that this is the first report of a group occurrence relating to agricultural workers. Although all of the patients improved after medical and surgical management, their vision was greatly decreased. It is suggested that the tropical climate, the harvest procedure, the characteristic monsoon, and lack of eye protection were involved. Therefore, the importance of the eye protection, hygiene education, and improving medical care to reduce the occurrence of fungal corneal ulcer in agriculture workers must be emphasised.

Clinical pharmacokinetics of fluconazole in superficial and systemic mycoses

The bis triazole agent fluconazole is used widely in the treatment of superficial and deep mycoses. A single oral dose of fluconazole 150 mg gives a mean long term clinical cure rate of 84 +/- 5% and is considered a valuable alternative to other topical antifungal drugs for vaginal candidiasis. A clinical cure rate of 90.4% for oropharyngeal candidiasis was obtained with 100mg daily for a minimum of 14 days; however, as for the other azoles the rate of relapse was large (40%) in immunocompromised patients. A daily dose of 100mg for at last 3 weeks gave satisfying outcomes for oesophageal candidiasis. Most patients (71 to 86%) with signs and symptoms of urinary tract candidiasis show beneficial clinical results when given oral fluconazole 50mg for several weeks. Fluconazole 50 to 150 mg given for weeks or months results in over 90% clinical cure or improvement for cutaneous mycosis including tinea, pityriasis, cryptococcosis and candidiasis. Prolonged (6 to 12 months) fluconazole 150 mg once a week is needed to treat onychomycosis successfully. Higher oral doses (200 to 400 mg daily) for long periods are generally used to treat deep mycoses such as meningitis, ophthalmitis, pneumonia, hepatosplenic mycosis and endocarditis. Fluconazole is effective for treating the fungal peritonitis which can complicate continuous ambulatory peritoneal dialysis (CAPD). A regimen of 50 mg intraperitoneally or 100 mg orally was used in these patients with impaired renal function. The dosage schedules used to treat disseminated fungal infections due to systemic mycoses with different or multiple foci of infections vary widely, with doses of 50 to 400 mg given orally or intravenously for between 1 week and several months. The most recent clinical reports have investigated the use of prophylaxis with fluconazole 100 to 400 mg daily, in immunocompromised patients. Fluconazole is found in body fluids such as vaginal secretions, breast milk, saliva, sputum and cerebrospinal fluid at concentrations comparable with those determined in blood after single or multiple doses. There is an excellent linear plasma concentration-dose relationship, but the mycological and clinical responses do not appear to be well correlated with the dose. A total maximum daily dose of 1600 mg is recommended to avoid neurological toxicity. Data from pharmacokinetic studies conducted in patients, mainly those with AIDS, and using a 1-compartment model give very constant parameters similar to those obtained in healthy individuals. Bioavailability, measured in HIV-positive patients and those with AIDS, exceeded 93% for tablets, suspension and suppositories. The time to reach peak plasma concentrations (tmax) was 2.4 to 3.7 hours. The peak plasma drug concentration (Cmax) obtained after a 100 mg oral dose was 2 mg/L. Areas under the concentration-time curve (AUC) obtained in different studies all correlate well with the dose (r = 0.926). The AUC determined after 200 and 25 mg suppositories were similarly well correlated. Hypochlorhydria does not affect the absorption of fluconazole, neither does food intake, race (Japanese or Caucasian) or gastrointestinal resection. Binding to plasma protein is low (11.14%) and is increased to 23% in cancer patients. Fluconazole is rapidly distributed to the tissue, where it accumulates. Tissues fall into 1 of 4 groups of increasing drug concentration: blood, bone and brain have the lowest concentrations, and spleen has the highest. The volume of distribution (Vd) remains stable at 46.3 +/- 7.9L and is considered to be an 'invariant' parameter across species. Fluconazole is poorly metabolised and is mainly eliminated unchanged in the urine. The percentage of the dose recovered in the urine in 48 hours is close to 60%. Concentrations in the urine are high and the half-life (t1/2) is long (37.2 +/- 5.5h) in patients, mainly those with AIDS, which is not significantly different from the t1/2 (31.4 +/- 4.7 hours) in healthy individuals. (ABSTRACT TRUN