Elution of Clindamycin and Enrofloxacin From Calcium Sulfate Hemihydrate Beads In Vitro.
OBJECTIVE
To compare the in vitro elution characteristics of clindamycin and enrofloxacin from calcium sulfate hemihydrate beads containing a single antibiotic, both antibiotics, and each antibiotic incubated in the same eluent well.


METHODS
Experimental in vitro study.


METHODS
Calcium sulfate hemihydrate beads were formed by mixing with clindamycin and/or enrofloxacin to create 4 study groups: (1) 160 mg clindamycin/10 beads; (2) 160 mg enrofloxacin/10 beads; (3) 160 mg clindamycin + 160 mg enrofloxacin/10 beads; and (4) 160 mg clindamycin/5 beads and 160 mg enrofloxacin/5 beads. Chains of beads were formed in triplicate and placed in 5 mL phosphate buffered saline (PBS; pH 7.4 and room temperature) with constant agitation. Antibiotic-conditioned PBS was sampled at 14 time points from 1 hour to 30 days. Clindamycin and enrofloxacin concentrations in PBS were determined using high-performance liquid chromatography.


RESULTS
Eluent concentrations from clindamycin-impregnated beads failed to remain sufficiently above minimum inhibitory concentration (MIC) for common infecting bacteria over the study period. Enrofloxacin eluent concentrations remained sufficiently above MIC for common wound pathogens of dogs and cats and demonstrated an atypical biphasic release pattern. No significant differences in elution occurred as a result of copolymerization of the antibiotics into a single bead or from individual beads co-eluting in the same eluent well.


CONCLUSIONS
Clindamycin-impregnated beads cannot be recommended for treatment of infection at the studied doses; however, use of enrofloxacin-impregnated beads may be justified when susceptible bacteria are cultured.
Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, Illinois.
Heidi
H
Phillips
Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, Alabama.
Dawn M
DM
Boothe
Lauderdale Veterinary Specialists, Ft. Lauderdale, Florida.
R Avery
RA
Bennett
D000900:Anti-Bacterial Agents / Q000737:chemistry*; D002133:Calcium Sulfate / Q000737:chemistry*; D002981:Clindamycin / Q000737:chemistry*; D004338:Drug Combinations; D000077422:Enrofloxacin; D024841:Fluoroquinolones / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D008863:Microspheres
D000900:Anti-Bacterial Agents; D004338:Drug Combinations; D024841:Fluoroquinolones; D000077422:Enrofloxacin; D002981:Clindamycin; D002133:Calcium Sulfate