Intraocular penetration of topical lidocaine 4%

Purpose: To evaluate the intraocular penetration of lidocaine 4% topically applied before phacoemulsification. Settings: Institute of Ophthalmology, University of Verona, and Department of Medical Pharmacology, University of Padua, Italy. Methods: Thirty eyes having phacoemulsification for senile cataract were anesthetized by topical application of lidocaine 4%. The drug was applied 3 times in 30 minutes in 15 eyes and 6 times in 60 minutes in 15 eyes. At the beginning of surgery, aqueous humor samples were obtained to measure the lidocaine levels. Blood samples were obtained in 6 patients 30 and 60 minutes after aqueous humor collection. The aqueous humor levels were compared with the amount of pain perceived by patients during surgery. Results: Mean aqueous humor lidocaine concentration was 8.68 mu g/mL +/- 2.43 (SD) after 3 instillations and 23.21 +/- 8.87 mu g/mL after 6 instillations. Blood levels of lidocaine were negligible. Patients whose intraocular level was below 12 mu g/mL perceived more pain during surgery. Only 2 eyes had these low levels after 6 instillations. Conclusions: Topically applied lidocaine 4% effectively penetrates the eye, providing analgesia for phacoemulsification. We suggest at least 6 instillations in the hour preceding surgery. In this study, pain during surgery was primarily related to poor intraocular levels of the anesthetic agent. J Cataract Refract Surg 1999; 25:643-647 (C) 1999 ASCRS and ESCRS.