Evaluation of the retinal toxicity and pharmacokinetics of dexamethasone after intravitreal injection
H. W. Kwak and D. J. D'Amico
Howe Laboratory of Ophthalmology, Massachusetts Eye and Ear Infirmary, Boston 02114.
The intravitreal injection of steroids may be potentially useful in the
treatment of endophthalmitis and other ocular inflammatory diseases. The
retinal toxicity and intraocular turnover of aqueous solutions of
dexamethasone sodium phosphate in doses ranging from 440 to 4000 micrograms
were evaluated in the rabbit; evaluation was also performed for a 0.1-mL
injection of a commercially available preparation (dexamethasone phosphate
[Decadron] injection, 4 mg/mL). After the 440-micrograms dose, a transient
increase in staining of the Muller cells was observed, which normalized
after 2 days. Progressively higher doses resulted in an increasing spectrum
of disorganization in Muller and other retinal cells. The half-life of the
intravitreally injected drug was 3.48 hours. These findings suggest a
primary interference in Muller cell function, possibly through
dexamethasone-induced alterations in retinal glutamate or glucose
metabolism.
