Transcorneal iontophoresis for delivery of ciprofloxacin hydrochloride.

PURPOSE: To investigate the feasibility of utilizing iontophoresis for delivery of ciprofloxacin hydrochloride to the anterior chamber of the eye and to carry out systematic studies to investigate the effect of electrical protocol on the transcorneal drug delivery. MATERIALS AND METHODS: Effect of current density (0.75 mA/cm(2) to 6.25 mA/cm(2) applied for 5 minutes) on drug permeation across the cornea and drug load in the cornea were investigated in vitro as well as ex vivo studies in porcine cornea model. Tolerability studies were carried out in rabbits. Cytotoxicity studies were conducted in cultured corneal tissue. RESULTS: The drug loaded in the cornea increased with increasing current density. After 5 minutes of iontophoresis, the drug concentration in the receiver compartment fluid (in vitro) or in aqueous humor (ex vivo) was not significantly higher than control (in which electric current was not applied). However, waiting for 6-12 hours after iontophoresis for 5 minutes, the concentrations of drug in aqueous humor in ex vivo studies were approximately 6 and approximately 5-fold higher than control (130.12 +/- 78.99 ng/ml), respectively. Cytotoxicity studies demonstrated the safety of the technique. The application of 6.25 mA/cm(2) for 5 minutes (right eye) did not show any sign of loss of vision and abnormal discharge, redness of eye, or edema when compared to the control left eye. CONCLUSIONS: Transcorneal iontophoresis is a potential method of delivering effective levels of ciprofloxacin hydrochloride into aqueous humor for the treatment of intraocular infections. This study unveils the ability of iontophoresis to rapidly drive ciprofloxacin into the cornea where a drug reservoir is formed, which eventually releases slowly into aqueous humor, eliciting sustained therapeutic effect.

Use of position and feature cues in discrimination learning by the whiptail lizard (Cnemidophorus inornatus).

Animals use a variety of cue types to locate and discriminate objects. The ease with which particular cue types are learned varies across species and context. An enormous literature contains comparisons of spatial cue use to use of other cue types, but few experiments examine the ease with which various nonspatial cues are learned. In addition, few studies have examined cue use in reptiles. Thus, the authors compared whiptail lizards' (Cnemidophorus inornatus) ability to learn and reverse a discrimination using either position (left or right) or visual feature cues. Lizards learned and reversed the task using position cues faster and with greater accuracy than using feature cues.