In vitro elution of gentamicin, amikacin, and ceftiofur from polymethylmethacrylate and hydroxyapatite cement

Release of daptomycin from polymethylmethacrylate beads in a continuous flow chamber

Because daptomycin is active against Gram-positive cocci, it may be useful in the treatment and prevention of bone and joint infections when incorporated into polymethylmethacrylate (PMMA). The release kinetics of daptomycin from PMMA were studied in a continuous flow chamber designed to simulate in vivo conditions. Three-millimeter beads containing 2.5%, 7.5%, and 15.0% daptomycin (weight daptomycin per weight PMMA) were individually placed in a chamber with 1 mL Krebs Ringer buffer flowing at 1 mL/hour. The majority of daptomycin was released in the first 24 hours. The mean peak concentrations were 13.4, 62.3, and 146.7 microg/mL; the mean AUC0-infinity were 30, 272, and 1204 h x microg/mL; and the mean percentages of daptomycin released were 6%, 18%, and 42% for the beads containing 2.5%, 7.5%, and 15.0% daptomycin, respectively. Daptomycin is released from PMMA in a continuous flow chamber at a rate similar to that previously determined by our laboratory for vancomycin.

Stabilisation of scoliosis in two koi (Cyprinus carpio )

Two koi (Cyprinus carpio) from the same pond developed similar lesions of scoliosis. Radiographic examinations showed that their spines had become malaligned as a result of vertebral compression fractures involving T14 to T16. The vertebrae in both fish were stabilised with screws, k-wire and polymethylmethacrylate. They both appeared to improve after surgery, but they began to decline and died within three months. A postmortem examination revealed multi-organ inflammation that was not associated with the surgical implants.

Repair of calvarial defects in rats by prefabricated hydroxyapatite cement implants

The aim of the present study was to test the hypothesis that calvarial defects can be repaired by using preformed implants of calcium phosphate bone cement (CPBC) in rats. Sixty adult female Sprague-Dawley rats received full-thickness calvarial nonhealing defects with a diameter of 8 mm. Three different CPBCs were used: group 1: tetracalcium phosphate-based powder; group 2: a blend of amorphous and crystalline calcium phosphate precursors; and group 3: an alpha-tricalcium phosphate (alpha-TCP)-based powder. Implants were left to cure for 25-40 min at room temperature in a silicon mold of 7.9 mm and inserted press fit into the defects. Fifteen animals served as unfilled controls. After 13, 26, and 52 weeks, the material was analyzed qualitatively by using surface-stained undecalcified thick-section specimens and quantitatively by using semiautomated histometry. Kruskal-Wallis tests were applied to compare mean values of periimplant bone formation at a significance level of p < 0.05. Three implants of group 1 fractured during insertion. Resorption of CPBC without complementary bone formation was noticed in these implants. Unfractured implants were resorbed with simultaneous apposition of bone on the implant surface. After 52 weeks, the resorption rate varied between 23.1 and 39.3%. Periimplant bone formation increased continuously on average around all implant types, but it reached statistical significance only in group 2. The results showed that repair of calvarial defects can be achieved by preformed CPBC implants. The rate of resorption of preformed implants is, however, much lower than that reported for in vivo cured CPBC.

Rabbit wound management

In conclusion, rabbits have a variety of common disease presentations that require wound management. Anatomic and physiologic characteristics should be kept in mind, as they may have influences upon the management of wounds. Many new topical medications and dressings have been designed that are routinely used in mammalian wound management cases and are potentially useful for rabbits. When topical medications are used in rabbits, care must be taken to ensure the medications are not ingested. In addition to topical therapies, surgical options such as flaps and skin grafts have been researched in rabbits. Many of the wound management concepts that are useful for dogs and cats should be considered when addressing rabbit wounds.

Elution of metronidazole and gentamicin from polymethylmethacrylate beads

OBJECTIVE

To characterize the elution and bioactivity of metronidazole and gentamicin sulfate polymerized, individually and in combination, with polymethylmethacrylate (PMMA).

STUDY DESIGN

In vitro experimental study.

METHODS

PMMA beads containing metronidazole (3 concentrations), gentamicin sulfate, or metronidazole and gentamicin sulfate were immersed in 5 mL of phosphate-buffered saline in triplicate. Eluent was replaced at specified time intervals for 1 or 21 days, and antibiotic concentrations were measured by high-performance liquid chromatography. Changes in antibiotic bioactivity attributable to polymerization or copolymerization of the antibiotics with PMMA, ethylene oxide sterilization, and storage of AIPMMA beads containing metronidazole were evaluated.

RESULTS

Antibiotic elution patterns were similar for all groups. Day 1 elution for groups containing metronidazole or gentamicin individually represented a mean 63%-66% and 79%, respectively, of the 21-day total. Approximately 50% of the day 1 elution occurred during the first hour. The elution of metronidazole was dose dependent. The elution of metronidazole (day 3-21) and gentamicin (all days) was significantly greater when metronidazole and gentamicin were combined (P <.05). The addition of metronidazole delayed polymerization of PMMA. Neither polymerization nor copolymerization of metronidazole and gentamicin with PMMA, gas sterilization, or 2-month storage of beads containing metronidazole significantly affected antimicrobial bioactivity.

CONCLUSIONS

Metronidazole elution from PMMA was dose dependent. Copolymerization of metronidazole and gentamicin sulfate in PMMA resulted in increased rates of elution. Intraoperative preparation of metronidazole-impregnated PMMA beads is not practical, but sterilization and storage for 2 months should not affect efficacy.

CLINICAL RELEVANCE

The local delivery of biologically active metronidazole and gentamicin by elution from PMMA is feasible.

In vitro elution of gentamicin from Plaster of Paris beads

OBJECTIVE

To determine the in vitro elution characteristics of gentamicin from Plaster of Paris-gentamicin (POP-gent) beads.

STUDY DESIGN

In vitro, controlled, experimental study.

METHODS

The POP-gent beads were made using a bead mold from 20 g calcium sulfate hemihydrate, 5 mL (500 mg) gentamicin solution, and 3 mL of phosphate buffered saline (PBS). Control beads were made similarly, using 30 g of dried powder and 8 mL of PBS. Beads were left in the mold overnight, gas-sterilized with ethylene oxide, and stored at room temperature for 5 months before testing. Bead chains were placed in sterile tubes containing porcine serum, and tubes were placed in a 37 degrees C incubator on a rocker. Serum was removed at intervals over 14 days and the concentration of gentamicin determined by fluorescent polarization immunoassay. Serum antibacterial activity was determined against an equine origin Escherichia coli.

RESULTS

POP-gent beads released gentamicin for the 14-day sampling period. Eighty percent of the gentamicin incorporated in the beads was released over the first 48 hours. Eluent from POP-gent beads inhibited the growth of E coli at all time periods. No gentamicin was eluted from control beads and control eluent did not inhibit growth of E coli.

CONCLUSIONS

In this experimental model, POP-gent beads released bactericidal drug for 14 days. Eighty percent of the gentamicin incorporated into the beads was released during the first 48 hours. The drug retains its bactericidal activity after ethylene oxide sterilization and storage at room temperature for up to 5 months.

CLINICAL RELEVANCE

Pop-gent beads may be a useful repository device to deliver gentamicin locally in tissues.

Gentamicin may have an adverse effect on osteogenesis

OBJECTIVE

To investigate the toxic effect of gentamicin at the high concentrations that can be achieved by local administration in the management of bone infection.

DESIGN

Randomized, prospective study in cultured cells, with drug exposure duration of 4 days.

SETTING

Cell culture in Dulbecco's modification of Eagle's minimal essential medium with supplements at 37 degrees C in air:CO2 (v:v, 95:5).

MATERIALS

Human osteoblastlike cells derived from cancellous bone collected from four adult patients without systemic disease during total hip replacement were cultured in antibiotic-free medium for 4 weeks.

INTERVENTION

The cultured cells were exposed to media containing various concentrations of gentamicin (0-1000 microg/mL) for 4 days.

MAIN OUTCOME MEASUREMENTS

Alkaline phosphatase activity, total DNA, and 3H-thymidine incorporation.

RESULT

Alkaline phosphatase activity was significantly decreased (p < 0.05) in all of the cultures at gentamicin concentrations of 100 microg/mL and above. 3H-thymidine incorporation was also decreased (p < 0.05) in three out of four cultures at 100 microg/mL and above. Total DNA was significantly decreased (p < 0.05) at 700 microg/mL and above.

CONCLUSION

Gentamicin, at high concentrations, as achieved following topical application, inhibits cell proliferation in vitro and, therefore, may be detrimental to the repair process in vivo.

The effect of storage temperatures on the in vitro properties of a polyanhydride implant containing gentamicin

Septacin is a biodegradable sustained-release implant containing 20% (w/w) gentamicin sulfate. The matrix of the implant is a polyanhydride copolymer composed of erucic acid dimer (EAD) and sebacic acid (SA) in a one-to-one weight ratio. The effect of storage temperatures (-15 degrees C and 25 degrees C) on the stability of Septacin was evaluated with respect to gentamicin potency, copolymer molecular weight, and in vitro drug release. The drug in polymer matrix was stable for at least 12 months when stored at 25 degrees C, but the molecular weight of the copolymer declined rapidly at this temperature. At -15 degrees C, there was no change in the molecular weight of the copolymer. However, the placebo (copolymer without gentamicin) exhibited a significant drop in copolymer molecular weight at both temperatures. The drug release profiles showed no change for samples stored at -15 degrees C for the duration of this study, while the release of drug slowed down significantly for samples stored at 25 degrees C for longer than one month. A pronounced difference in the morphology of the -15 degrees C samples and the 25 degrees C samples was observed during the in vitro dissolution test; cracking of the -15 degrees C samples was evident, but the 25 degrees C samples remained intact.