Cefoxitin levels in human aqueous humor

Area of Science:

• Ophthalmology
• Pharmacology
• Infectious Diseases

Background:

• Cataract surgery requires effective perioperative antibiotic prophylaxis.
• Cefoxitin is a cephalosporin antibiotic used for surgical prophylaxis.
• Understanding cefoxitin's penetration into the aqueous humor is crucial for optimizing its use.

Purpose of the Study:

• To evaluate the aqueous humor concentrations of cefoxitin following a 2-g dose.
• To determine the impact of probenecid co-administration on cefoxitin aqueous humor levels and duration.
• To assess the achievement of therapeutic antibiotic levels against common ocular pathogens.

Main Methods:

• A prospective study involving 48 patients undergoing cataract surgery.
• Group 1: 25 patients received a 2-g dose of cefoxitin.
• Group 2: 23 patients received 500 mg of probenecid followed by a 2-g dose of cefoxitin.
• Aqueous humor samples were collected at various time points (30 minutes, 1, 2, 4, 6 hours) post-injection.
• Antibiotic concentrations were measured using validated assays.

Main Results:

• Average cefoxitin aqueous humor levels peaked at 3.16 µg/ml at one hour post-dose without probenecid.
• Probenecid significantly prolonged the duration of detectable cefoxitin in the aqueous humor.
• Therapeutic levels against gram-positive pathogens were achieved by 2 hours without probenecid and persisted from 2 to 4 hours with probenecid.
• Antibiotic levels effective against Enterobacteriaceae were inconsistent in both groups.

Conclusions:

• A 2-g dose of cefoxitin provides adequate aqueous humor concentrations for cataract surgery prophylaxis.
• Probenecid enhances the duration of therapeutic cefoxitin levels, potentially improving coverage against susceptible gram-positive organisms.
• The efficacy of cefoxitin against Enterobacteriaceae in the aqueous humor remains a concern.