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Effect of intravitreal dexamethasone on vitreous vancomycin concentrations in patients with suspected postoperative
Ivan M Gan1, Luana C Ugahary, Jaap T van Dissel
1The Rotterdam Eye Hospital, PO Box 70030, 3000 LM, Rotterdam, The Netherlands.
Purpose:
To study intravitreal dexamethasone and vancomycin concentrations, when used together in patients with suspected postoperative bacterial endophthalmitis. Animal studies had suggested that dexamethasone might decrease the concentration of vancomycin.
Design:
Prospective randomized clinical trial in a tertiary referral center.
Methods:
Twenty-nine consecutive patients with suspected postoperative bacterial endophthalmitis underwent a vitreous biopsy followed by intravitreal injection of antibiotics (0.2 mg vancomycin, 0.05 mg gentamicin) and 400 mug dexamethasone or placebo. After 3-4 days, the intravitreal injection of antibiotics and dexamethasone or placebo was repeated. In 18 patients, a second biopsy was taken for repeat culture and measurement of vancomycin and dexamethasone concentrations.
Results:
In 20/29 patients (69%) the first vitreous cultures were positive; the second culture was negative in all cases. Thirteen out of 29 patients received dexamethasone. Dexamethasone concentrations showed an average of 25 ng/ml 3 days after injection, with an estimated half-life of 5.5 h. Vancomycin concentrations in patients given dexamethasone tended to be higher compared with those in the placebo group (P=0.061).
Conclusion:
Intravitreal dexamethasone does not lead to decreased vancomycin concentrations, when given simultaneously in the treatment of patients with suspected bacterial endophthalmitis.