Intravitreal vancomycin and gentamicin concentrations in patients with postoperative endophthalmitis.
OBJECTIVE
To study the intravitreal antibiotic concentrations and the efficacy of an intravitreal dosing regimen to treat patients with postoperative bacterial endophthalmitis. This regimen, based on pharmacokinetic/pharmacodynamic considerations, relies on a repeat antibiotic injection of a lower dose than is generally used.


METHODS
In consecutive patients with suspected postoperative endophthalmitis a vitreous biopsy for bacterial culture was taken before 0.2 mg vancomycin and 0.05 mg gentamicin were injected intravitreally. After 3 or 4 days a second biopsy was taken for bacteriological culture and to measure intravitreal vancomycin and gentamicin concentrations, followed by a repeat injection of 0.2 mg vancomycin.


RESULTS
17 patients entered the study. In 11 patients the initial bacterial culture was positive, predominantly coagulase negative staphylococci. All second vitreous biopsies were sterile. Intravitreal vancomycin levels varied between 2.6 and 18.0 microg/ml (mean 10.3 (SD 4.1) microg/ml) after 3 days and between 3.1 and 16.6 microg/ml (mean 7.5 (6.2) microg/ml) after 4 days which is well above the minimal inhibitory concentration for most micro-organisms. Concentrations of intravitreal gentamicin varied between 0.90 and 3.3 microg/ml (mean 1.6 (0.72) microg/ml) after 3 days and between 1.2 and 2.6 microg/ml (mean 1.9 (0.99) microg/ml) after 4 days.


CONCLUSIONS
This dosing regimen resulted both in adequate intravitreal vancomycin and gentamicin levels for over a week as well as in negative second cultures. This study also provides new information on intravitreal vancomycin and gentamicin concentration over time in patients with postoperative endophthalmitis.
Gan
I M
IM
Department of Infectious Diseases, The Rotterdam Eye Hospital, PO Box 70030, 3000 LM Rotterdam, Netherlands.
van Dissel
J T
JT
Beekhuis
W H
WH
Swart
W
W
van Meurs
J C
JC
D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics* / Q000627:therapeutic use; D001706:Biopsy; D002387:Cataract Extraction / Q000009:adverse effects; D015169:Colony Count, Microbial; D009877:Endophthalmitis / Q000188:drug therapy / Q000378:metabolism*; D005260:Female; D016231:Fluorescence Polarization Immunoassay; D005839:Gentamicins / Q000493:pharmacokinetics* / Q000627:therapeutic use; D006801:Humans; D007267:Injections; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D016896:Treatment Outcome; D014640:Vancomycin / Q000493:pharmacokinetics* / Q000627:therapeutic use; D014822:Vitreous Body / Q000378:metabolism* / Q000473:pathology
D000900:Anti-Bacterial Agents; D005839:Gentamicins; D014640:Vancomycin