Pharmacokinetic analysis of topical tobramycin in equine tears by automated immunoassay

Czerwinski, Sarah L.; Lyon, Andrew W.; Skorobohach, Brian J.; Léguillette, Renaud

doi:10.1186/1746-6148-8-141

Cited by 1 publication

(2 citation statements)

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“…Most described topical ophthalmic regimens used for treating equine individuals with ocular diseases are primarily formulated for use in humans [ 9 , 10 ]. Therefore, topical tobramycin is frequently used empirically for the treatment of ocular disorders in equines [ 11 ]. Tobramycin is a broad-spectrum aminoglycoside antibiotic [ 12 ].…”

Section: Introductionmentioning

confidence: 99%

“…It has been noted that tobramycin MIC90 concentration (minimal inhibitory concentration to 90% of microbial growth) in tears and in vitro declines rapidly following topical administration [ 14 – 16 ]. A topical single dose of tobramycin gives rise to a higher therapeutic concentration in the tears of horses for 1 h (h) after administration with a concentration kept above the MIC90 for mostly isolated bacteria for 68.5 min (min) [ 11 ]. However, these levels were maintained in equine tears 6 times longer than in rabbit tears [ 15 ].…”

Section: Introductionmentioning

confidence: 99%

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Impact of pH modification of the empirically used tobramycin ophthalmic solution on MIC90 concentration in tears and aqueous humor of donkeys (Equus asinus)

Ibrahim,

Abd-Elrasoul,

Sabra

2024

BMC Vet Res

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Background Commercial tobramycin ophthalmic solution is frequently used empirically to treat ocular disorders in equines, despite being primarily formulated for use in humans. It has been noted that tobramycin MIC90 concentration (minimal inhibitory concentration to 90% of microbial growth) rapidly declined following topical administration. It is hypothesized that adjustment of the pH of the empirically used tobramycin ophthalmic solution -prepared for human use- with the pH of the tears of donkeys, could increase the bioavailability of the drug and subsequently improve its penetration to the aqueous humor. Therefore, this study aimed to evaluate the impact of pH adjustment of the empirically used tobramycin ophthalmic solution on MIC90 concentration in tears and aqueous humor of donkeys (Equus asinus). The study was conducted on six (n = 6) clinically healthy donkeys. In each donkey, one eye was randomly selected to receive 210 µg tobramycin of the commercial tobramycin (CT) and used as a positive control (C group, n = 6). The other eye (treated eye) received 210 µg of the modified tobramycin ophthalmic solution (MT) (T group, n = 6). Tears and aqueous humor samples were collected 5-, 10-, 15-, 30- min, and 1-, 2-, 4-, and 6 h post-instillation. Results Modifying the pH of the empirically used commercial tobramycin ophthalmic solution in donkeys at a pH of 8.26 enhanced the drug’s bioavailability. The MIC90 of the most hazardous bacteria isolated from equines’ eyes such as Pseudomonas aeruginosa (MIC90 = 128 µg/ml) and Staphylococcus aureus (MIC90 = 256 µg/ml) was covered early (5 min post-instillation) and over a longer period in donkey tears (239–342 min) and aqueous humor (238–330 min) with the modified tobramycin solution. Conclusions Adjustment of the pH of the commercial tobramycin ophthalmic solution, empirically used by veterinarians to treat donkeys’ ophthalmic infections at a pH of 8.26, isotonic with the donkeys’ tears pH, resulting in higher concentrations of tobramycin in tears and aqueous humor for a longer time.

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