Drug binding of ophthalmic viscoelastic agents

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.