Fortified antibiotic advance improves corneal infection treatment paradigm

Fortified antibiotics are used in these cases to prevent permanent damage and vision loss. (Adobe Stock / PixieMe)

Corneal ulceration secondary to infectious keratitis is a painful and vision-threatening condition. Most corneal ulcers in the United States are associated with contact lens use and poor hygiene. Historically, corneal ulcer management has been dictated by a treatment algorithm that considers size and location of the ulcer—generally, if concerning, the infiltrate is cultured and the patient is prescribed fortified antibiotics. The acquisition and provision of fortified antibiotics recently has been simplified, resulting in a practice paradigm shift replete with potential vision-saving benefits.

Corneal ulcer management

If the corneal ulcer is peripheral and less than 1 mm, it is typically not vision-threatening if treated appropriately. In such a case, I skip the culture and prescribe a fourth-generation fluoroquinolone such as gatifloxacin or moxifloxacin every hour for the first day and then taper based on response to treatment. Conversely, when a patient presents with an ulcer greater than 1 mm and/or central in location (Figure), I culture it to determine which pathogen is causing the infection and then get the patient on a fortified antibiotic immediately. Fortified antibiotics are compounded to deliver increased concentrations of medication to the cornea in situations where commercially available antibiotics may be insufficient for treating the infection.

Historically, the steps involved in carrying out the fortified antibiotic treatment plan were inefficient for the physician and a burden to the patient. After we ordered the fortified antibiotic from a compounding pharmacy, the patient or caregiver had to travel to that pharmacy—sometimes 2 hours away—to retrieve the customized eye drops. Timely administration of the medication is critical because these large, central corneal ulcers can threaten vision and progress rapidly. In regions with limited access to fortified antibiotics, we often start patients on commercially available topical treatment while spending hours searching for a pharmacy that may be able to deliver.

Fortified antibiotic development

A recent development has improved the treatment outlook for our patients who present with vision-threatening corneal ulcers. We now can stock the fortified, high-concentration tobramycin 1.5% + vancomycin 5% compounded antibiotic formulation (Fortisite; ImprimisRx) in our clinics for immediate treatment.

Tobramycin 1.5% + vancomycin 5% is distributed through an FDA-registered and -inspected 503B outsourcing facility. The formula is tested for potency and sterility before dispensing and is stable at refrigerated temperatures (5 °C) for up to 180 days. Because tobramycin 1.5% + vancomycin 5% compounded antibiotic formulation is now available for in-office use from an FDA-registered 503B outsourcing facility, each bottle must strictly adhere to rigorous analytical testing protocols that are not required for local compounding pharmacies.

There are important benefits associated with this advance: When a fortified antibiotic is called for, the delay in administering appropriate treatment is eliminated and the logistical burden on the patient is eradicated. These advantages are more significant for some practices than others. For instance, in a large metropolitan area such as Philadelphia, Pennsylvania, where I practice, corneal ulcer cases often get referred to tertiary medical centers because those facilities can create fortified antibiotics and/or perform the culture. Stocking a fortified antibiotic in my clinic lets me treat and retain these patients.

For practices that are either not comfortable with the 503B pharmacy process or are unprepared to stock the medication, there is an alternative that is still an improvement. Eye care providers can order Fortisite directly through the ImprimisRx 503A pharmacy and have it shipped overnight to the patient. Therefore, even physicians who do not want to stock the fortified antibiotic can reduce the logistical burden on their patients and get the drug to them quickly.

No two corneal ulcers are alike, but if they are large and central then time is of the essence. Fortified antibiotics are used in these cases to prevent permanent damage and vision loss. Private practice eye care providers’ ability to immediately administer antibiotic eye drops or have them overnighted to the patient is a giant step forward for practice and patient.