[99mTc-ceftizoxime scintigraphy in normal rats and abscess induced rats]. / Gammagrafía con 99mTc-ceftizoxima en ratas normales y en ratas con absceso inducido.

UNLABELLED: This study aimed to investigate the biodistribution of the 99mTc-ceftizoxime in normal rats and in rats bearing septic and sterile induced abscess. MATERIAL AND METHODS: Three groups of rats were studied. a) Six normal rats b) 15 rats with E. coli induced abscess and c) 15 rats with sterile zymosan induced abscess. Septic abscess was induced with 2 x 10(8) colony forming units of E. coli and sterile one with 0.1 mL of 5% sterile Zymosan. 24 h after the abscess induction, 12 MBq of 99mTc-CFT were injected iv. and whole body images were collected at 30 min, 1, 2, 4 and 6 h p.i. Areas of interest were drawn and lesion/background index was calculated. The 6 normal rats were scanned at the same times, killed at 6 h p.i and kidney, liver, spleen, lung, heart and muscle activity were measured. Each organ was weighed, cut and its activity measured. Parallelly, the biological activity of the labeled antibiotic and its binding to the E. coli and S. aureus bacteria were analyzed. RESULTS: High biliary excretion was seen in all rats. Organ measurement showed the maximal uptake in kidney and very low uptake in muscles. Mean +/- s.d abscess/background ratio at 30 min, 1, 2, 4 and 6 h were 2.60 +/- 0.36, 2.67 +/- 0.66, 2.6 0 +/- 0.58, 2.78 +/- 0.84, 3.24 +/- 1.00 for septic abscess and 2.37 +/- 0.39, 2.10 +/- 0.38, 1.97 +/- 0.34, 1.82 +/- 0.25, 1.65 +/- 0.23 for aseptic abscess. The 99mTc-CFT uptake was significantly higher in the septic abscess than in sterile one (p < 0.05). The 99mTc-CFT uptake in the septic abscess remains stable or increases until along the 6 h. The 99mTc-CFT uptake in the aseptic abscess decreases along the time. CONCLUSIONS: The scintigraphy with 99mTc-CFT seems able to differentiate sterile inflammation from infection. High biliary excretion limits its application in abdomen. Main application could be diagnosis of osteoarticular infection.

Gammagrafía con 99mTc-ceftizoxima en ratas normales y en ratas con absceso inducido / 99mTc-ceftizoxzime scintigraphy in normal rats and abscess induced rats

El objetivo del trabajo fue analizar la biodistribución de la 99mTc-ceftizoxima (CFT) en ratas normales y en ratas con absceso inducido: séptico o estéril. Material y métodos: Se estudiaron 3 grupos de ratas. a) 6 ratas normales; b) 15 ratas en las que se indujo un absceso séptico con 2 x 10 8 unidades formadoras de colonias de Escherichia coli, y c) 15 ratas en las que se indujo un absceso estéril con 0,1 ml de 5 % zymosan estéril. A las 24 h de la inducción del absceso se inyectaron i.v. 12 MBq de 99mTc-CFT y se registraron imágenes de cuerpo entero a los 30 min y 1, 2, 4 y 6 h p.i. Se dibujaron áreas de interés y se calculó el índice lesión/fondo. En las 6 ratas normales se siguió el mismo procedimiento y además al finalizar las últimas imágenes se sacrificaron y se extrajeron riñones, hígado, bazo, corazón pulmones y un fragmento de músculo. Cada órgano, fue pesado, cortado y se midió la actividad que contenía. Paralelamente se analizó la actividad biológica del antibiótico marcado y la unión del mismo a las bacterias E. coli y Staphylococcus aureus. Resultados: Se observó eliminación biliar elevada en todos los animales. El contaje de los órganos mostró la mayor actividad en riñones y actividad muy baja en músculo. El índice medio de actividad lesión/fondo (Media ± d.e.) a los 30 min, 1, 2, 4 y 6 h fue 2,60 ± 0,36, 2,67 ± 0,66, 2,6 0 ± 0,58, 2,78 ± 0,84, 3,24 ± 1,00 en el absceso séptico y 2,37 ± 0,39, 2,10 ± 0,38, 1,97 ± 0,34, 1,82 ± 0,25, 1,65 ± 0,23 en el absceso estéril. La captación de 99mTc-CFT fue significativamente mayor en el absceso séptico que en el estéril (p < 0,05). La captación de 99mTc-CFT en el absceso séptico se incrementa con el tiempo hasta las 6h, mientras que en el estéril disminuye con el tiempo. Conclusión: La gammagrafía con 99mTc-CFT permite diferenciar la inflamación estéril de la infección y se podría aplicar al diagnóstico de la infección osteo-articular. La elevada eliminación renal y biliar limita su aplicación en abdomen

This study aimed to investigate the biodistribution of the 99mTc-ceftizoxime in normal rats and in rats bearing septic y sterile induced abscess. Material y methods: Three groups of rats were studied. a) Six normal rats b) 15 rats with E. coli induced abscess and c) 15 rats with sterile zymosan induced abscess. Septic abscess was induced with 2 x 10 8 colony forming units de E.Coli y sterile one with 0.1 mL de 5 % sterile Zymosan. 24 h after the abscess induction, 12 MBq de 99mTc-CFT were injected iv. and whole body images were collected at 30 min, 1, 2, 4 and 6 h p.i.. Areas of interest were drawn and lesion/background index was calculated. The 6 normal rats were scanned at the same times, killed at 6 h p.i. and kidney, liver, spleen, lung, heart and muscle activity were measured. Each organ was weighed, cut and its activity measured. Parallelly, the biological activity of the labeled antibiotic and its binding to the E. coli and S. aureus bacteria were analyzed. Results: High biliary excretion was seen in all rats. Organ measurement showed the maximal uptake in kidney and very low uptake in muscles. Mean ± s.d abscess/background ratio at 30 min, 1, 2, 4 and 6 h were 2.60 ± 0.36, 2.67 ± 0.66, 2.6 0 ± 0.58, 2.78 ± 0.84, 3.24 ± 1.00 for septic abscess and 2.37 ± 0.39, 2.10 ± 0.38, 1.97 ± 0.34, 1.82 ± 0.25, 1.65 ± 0.23 for aseptic abscess. The 99mTc-CFT uptake was significantly higher in the septic abscess than in sterile one (p < 0.05). The 99mTc-CFT uptake in the septic abscess remains stable or increases until along the 6 h. The 99mTc-CFT uptake in the aseptic abscess decreases along the time. Conclusions: The scintigraphy with 99mTc-CFT seems able to differentiate sterile inflammation from infection. High biliary excretion limits its application in abdomen. Main application could be diagnosis of osteoarticular infection

Marcaje de ceftizoxima con 99mTc / Labelling of ceftizoxime with 99mTC

Se presenta un nuevo método de marcaje de antibióticos con 99mTc. Una cefalosporina de 3.ª generación de amplio espectro (ceftizoxima).Material y métodos: Se han utilizado 2,5 mg de ceftizoxima, 6,25 mg de ditionito sódico en una solución tampón (pH 11,4) como agente reductor y 300 MBq de 99mTc. El pH final se ajustó a 8,4 con NaOH 0,1N. La solución resultante fue hervida a 100ºC durante 5 min. La pureza radioquímica se valoró usando ITLC-SG/MEK, ITLC-SG/ 0,9 por ciento NaCl y HPLC fase reversa. La actividad biológica se valoró mediante la técnica de difusión en agar impregnadas con E. Coli de discos conteniendo 10,5 µg de antibiótico marcado y sin marcar. El mantenimiento de la actividad biológica fue evaluado por el diámetro de inhibición de los halos obtenidos tras 24 horas de incubación. Resultados: La eficiencia de marcaje fue de 94,9 ñ 2,4 por ciento (n = 20) y el compuesto mantuvo la estabilidad hasta 6 h. La cromatografía HPLC mostró 5 picos: dos a 1,7-2,0 min corresponden al compuesto derivado de la ceftizoxima (CDC) (82 por ciento-83 por ciento de la absorbancia y alrededor del 90 por ciento de la radioactividad), otro a los 4,7 min corresponde a la ceftizoxima intacta (6 por ciento de la absorbancia). Los dos picos restantes, aparecen a los 3,8 y 6,7 min y representan alrededor del 7-8 por ciento de la absorbancia. La actividad biológica del CDC respecto al antibiótico no marcado fue del 83 por ciento. Conclusiones: 1) El método de marcaje descrito da lugar a una modificación de la estructura de la ceftizoxima. 2) El 99m Tc se une a la nueva especie formada con un elevado rendimiento de marcaje y aceptable estabilidad. 3) El 99mTc-CDC mantiene 83 por ciento de la actividad antibiótica original y podría ser utilizado para la detección de infección in vivo (AU)

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[Labelling of ceftizoxime with 99mTc]. / Marcaje de ceftizoxima con 99mTc.

AIM OF THE STUDY: A new method to label antibiotics with 99mTc, using a third generation, wide spectrum cephalosporine (ceftizoxime), is presented. MATERIAL AND METHODS: 2.5 mg of ceftizoxime, 6.25 mg sodium dithionite in sodium bicarbonate buffer (pH=11.4) as a reductor agent, and 300 MBq of 99mTc were used. The final pH was adjusted to 8.4 with NaOH 0.1N. Radiochemical purity was assessed using ITLC-SG/MEK, ITLC-SG/0.9% NaCl and reverse phase HPLC. Biologic activity was assessed with the agar diffusion technique soaked with E. Coli in disks containing 10.5 microg labelled and non-labelled antibiotic. The maintenance of antibiotic activity was assessed by the diameter of the inhibition halos measured after 24 hours of incubation at 37 degrees C. RESULTS: The labelling efficiency was 94.9 +/- 2.4% (n = 20) and the complex was stable up to 6 h post-labelling. The HPLC chromatography showed five peaks: two of them at 1.7-2.0 min, which corresponds to the ceftizoxime derived product (82%-83% of the absorbance and about 90% of the radioactivity) and a third one at 4.7 min which corresponds to the intact ceftizoxime (6% of absorbance). The remaining two peaks appeared at 3.8 and 6.7 min and represented about 7%-8% of the absorbance. The antibiotic activity of the ceftizoxime-derived compound (CDC) was 83% of the unlabelled one. CONCLUSIONS: 1) The labelling method of ceftizoxime described causes a modification in its structure. 2) The 99mTc binds to the newly formed compound with high labelling efficiency and an acceptable shelf life stability. 3) The 99mTc-CDC maintains 83% of the original antibiotic activity and could be used for the detection of in vivo infection.

[Validation of the preparation of individual doses of 51Cr-EDTA in syringes]. / Validación de la preparación de dosis individuales de 51Cr-EDTA en jeringas.

The 51Cr-EDTA is one of the radiopharmaceuticals more used in the glomerular filtration rate determination. The necessity to prepare a daily reference dose every time that are prepared the patient's doses can go to a poor exploitation of the multidose vial. One way of improving its use consists on the preparation of individual doses in ready syringes to inject, for several days, employing only one of them as a standard. The aim of this study was to evaluate the storing of 51Cr-EDTA individual doses at room temperature and at 4 degrees C during 4 weeks, analyzing the radiochemical purity, the sterility and the radiopharmaceutical retention into the syringe. The results obtained showed that the radiochemical purity remains stable, always been greater than the value recommended for its use (> 95%). Likewise, there were not microorganism contamination nor 51Cr-EDTA appreciable retention into the syringes. We concluded that the preparation of individual doses of 51Cr-EDTA in syringes and their conservation at room temperature, or at 4 degrees C, during a period of 4 weeks, neither influence in the radiopharmaceutical quality nor increase its retention into the syringe.