Sustained Tear Film Exposure After Parenteral Cefovecin Administration in Dogs: Pharmacokinetics and Relevance to Canine Bacterial Keratitis.

Cefovecin may adjunctively treat susceptible Streptococcus and Staphylococcus keratitis, but empiric systemic use is not justified.

This prospective pharmacokinetic study evaluated tear film concentrations of parenterally administered cefovecin (8 mg/kg SC) in six healthy Beagles following histamine-induced conjunctivitis to simulate blood-tear barrier disruption. Tear fluid was collected via Schirmer strips at multiple time points over 336 hours and analyzed using liquid chromatography-mass spectrometry. A pilot experiment demonstrated that barrier disruption significantly enhanced tear drug penetration, with concentrations 1.5- to 430-fold higher in the inflamed eye compared to the control eye. Across all dogs, tear cefovecin concentrations ranged from 68 to 73,035 ng/mL and remained detectable throughout the entire 336-hour study period. Key pharmacokinetic parameters included a peak concentration (Cmax) of 27.23 ± 27.74 μg/mL, Tmax of 61 ± 83 hours, AUC of 2,734 ± 2,563 μg/mL·h, and half-life of 64 ± 46 hours. MIC testing against 10 isolates each of Staphylococcus pseudintermedius, Streptococcus canis, and Pseudomonas aeruginosa revealed that tear concentrations exceeded the MIC for Streptococcus canis (0.64 μg/mL) for the full 336 hours and surpassed the MIC for some Staphylococcus pseudintermedius isolates (10.2 μg/mL) between 48 and 120 hours. Concentrations never achieved inhibitory levels against Pseudomonas aeruginosa. The authors conclude that cefovecin may serve as an adjunctive therapy in select cases of bacterial keratitis caused by susceptible organisms, but caution against empiric systemic antimicrobial use pending larger clinical validation studies.

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