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Pharmacokinetics of aztreonam in rabbit eyes
Abstract:
Subconjunctival injection of 100 mg of aztreonam in rabbits with Pseudomonas aeruginosa endophthalmitis produced transiently high antibiotic concentrations in most intraocular sites. Concentrations of approximately 2.5 micrograms/ml were achieved in the vitreous humor 15 min after injection and persisted for 6 h. Repeated intramuscular injections in dosages of 25 mg/kg every 4 h resulted in drug concentrations in the vitreous humor of 2.4 micrograms/ml in infected eyes. These levels might be adequate for the treatment of intraocular infections caused by highly susceptible organisms. Direct intravitreal injection of 100 micrograms of aztreonam in normal rabbit eyes produced an estimated peak concentration in the vitreous humor of 62 micrograms/ml, with a half-life of 7.5 h, which declined to 6 micrograms/ml by 48 h. The pharmacokinetic indices suggest that, like other beta-lactam antibiotics, aztreonam is eliminated from the vitreous humor by the retinal route. This novel antibiotic warrants further study of its efficacy and toxicity to determine whether it may be a useful alternative to the aminoglycosides for selected cases of ocular infection.
Insights
Aztreonam demonstrates promising intraocular antibiotic concentrations following subconjunctival injection in rabbits with Pseudomonas aeruginosa endophthalmitis. These levels suggest potential efficacy for treating ocular infections.
Area of Science:
- Ophthalmology
- Pharmacology
- Microbiology
Background:
- Endophthalmitis, an intraocular infection, poses a significant threat to vision.
- Pseudomonas aeruginosa is a common and aggressive pathogen causing severe ocular infections.
- Current treatments for ocular infections often involve aminoglycosides, which can have toxicity concerns.
Purpose of the Study:
- To evaluate the intraocular pharmacokinetics of aztreonam after subconjunctival and intramuscular administration in rabbits.
- To determine if aztreonam concentrations achieve therapeutic levels in the vitreous humor for treating Pseudomonas aeruginosa endophthalmitis.
- To explore aztreonam as a potential alternative to aminoglycosides for ocular infections.
Main Methods:
- Subconjunctival injection of 100 mg aztreonam in rabbits with experimentally induced Pseudomonas aeruginosa endophthalmitis.
- Repeated intramuscular injections of 25 mg/kg aztreonam every 4 hours in infected rabbits.
- Direct intravitreal injection of 100 micrograms aztreonam in normal rabbit eyes to assess vitreous pharmacokinetics.
- Antibiotic concentrations in various intraocular sites, particularly the vitreous humor, were measured over time.
Main Results:
- Subconjunctival aztreonam achieved transiently high concentrations in most intraocular sites, with vitreous levels around 2.5 micrograms/ml at 15 minutes, persisting for 6 hours.
- Intramuscular injections resulted in vitreous aztreonam concentrations of approximately 2.4 micrograms/ml in infected eyes.
- Direct intravitreal injection yielded a peak vitreous concentration of 62 micrograms/ml with a half-life of 7.5 hours, declining to 6 micrograms/ml by 48 hours.
- Pharmacokinetic data suggest elimination via the retinal route, similar to other beta-lactam antibiotics.
Conclusions:
- Aztreonam administered via subconjunctival injection achieves significant intraocular concentrations, including in the vitreous humor.
- Achieved vitreous concentrations may be adequate for treating ocular infections caused by susceptible organisms.
- Aztreonam shows potential as a novel therapeutic option for ocular infections, warranting further investigation into its efficacy and safety compared to aminoglycosides.