Drug binding of ophthalmic viscoelastic agents
M. L. McDermott and H. F. Edelhauser
Department of Ophthalmology, Medical College of Wisconsin, Milwaukee 53226.
When viscoelastic agents that contain hyaluronate sodium are used during
anterior segment surgical procedures, it is common for some of the material
to remain intraocularly after the surgery is completed. A variety of drugs,
used intracamerally or topically following surgery, are also present. These
drugs may be bound to the polyanionic hyaluronate molecule. This occurrence
may cause drug alterations in therapeutic effectiveness, pharmacokinetics,
and toxicity. To investigate the possibility for drug-viscoelastic agent
adsorption, in vitro drug-binding studies were performed on three
commercial viscoelastic agents; undiluted aliquots of Amvisc, Healon, or
Viscoat were mixed with radiolabeled D-threo-chloramphenicol,
dexamethasone, L-epinephrine, or pilocarpine hydrochloride, placed in
dialysis membranes, and dialyzed for 24 hours against an isotonic phosphate
buffer. The calculated drug binding by a viscoelastic agent ranged from 0%
to 1.5%. These extremely low values for in vitro drug uptake by
viscoelastic agents made it unlikely that any significant drug-viscoelastic
agent interaction would occur in the postoperative eye.
