TOPICAL BUPIVACAINE AND PROPARACAINE - A COMPARISON OF TOXICITY, ONSET OF ACTION, AND DURATION OF ACTION

Bupivacaine is a local ocular anesthetic with a long duration of actio n when administered by retrobulbar injection. To determine the potenti al for the use of bupivacaine as a topical ocular anesthetic, the onse t and duration of action and toxicity of various concentrations of bup ivacaine were studied after instillation in rabbit eyes. The onset and duration of action were not significantly different from that of topi cal 0.5% proparacaine. Increasing the pH of the bupivacaine solution f rom 5.7 to 6.5 nearly doubled the duration of action, but the increase was not sufficient to be clinically important. Slit lamp biomicroscop ic examination and scanning electron microscopy showed that bupivacain e was less toxic to the corneal epithelium than 0.5% proparacaine. Hea ling after keratectomy was significantly more rapid in eyes treated wi th 0.75% bupivacaine, compared with eyes treated with 0.5% proparacain e. These results suggest that bupivacaine may be less toxic to the cor neal epithelium than proparacaine and could be clinically useful for t opical ocular anesthesia, particularly if pharmacologic modifications can increase the duration of anesthesia provided by this drug.