Injection volume and intracameral moxifloxacin dose.

PURPOSE: To test the effect of injection volume and concentration on dosing and residence time of moxifloxacin in the anterior chamber (AC).

SETTING

Kaiser Permanente, Walnut Creek, California, USA.

DESIGN

Experimental study.

METHODS

Moxifloxacin 0.5%/0.05 mL, moxifloxacin 0.5%/0.10 mL, and moxifloxacin 0.15%/0.50 mL were drawn into 5 1.0 mL syringes each, injected into tared vials, and weighed. The doses delivered were calculated. The AC concentrations and elimination rates of the drug for two AC volumes were modeled for each dosing method.

RESULTS

The 0.05 mL injection volume resulted in the greatest range (35 μg) of delivered dose compared with larger injection volumes (≤25 μg). The mathematical model predicted that variation in dosing in each group would result in differences of 12 minutes or less for the presence of the drug in the AC. Injection of 0.5%/0.1 mL produced AC concentrations above 500 μg/mL for 1.9 to 3.0 hours and above 64 μg/mL for 5.5 to 6.5 hours, depending on the AC volume; however, flushing with a 0.15% concentration sustained AC levels for 1.9 hours and 5.5 hours, respectively, for the two AC volumes.

CONCLUSIONS

Smaller injection volumes of a higher concentration moxifloxacin resulted in less accuracy and less precision in the delivered dose (0.05 mL, P = .005; 0.10 mL, P = .03); however, the clinical significance of this might vary. Injection of 0.5%/0.1 mL and flushing with 0.15%/0.5 mL of moxifloxacin would provide similar drug AC residence times according to the model. Flushing provided more consistent AC concentrations with differing AC volumes.