Biodistribution of radio-labeled rifampicin in animals.
Throughout the duration of the trial, the rats were in good health. Animals ”exhibited normal feed consumption” and was well-tolerated. There was no influence on body weight during the trial period, and the body weight was unrelated to dose amounts.
Figure 5 represents the distribution of labeled rifampicin in percentage administered dose per gram of organ (%AD/g). Approximately 2.7%, 1.24%, 0.58%, 0.5%, and 0.99% drug was found in lungs, liver, thyroid, kidneys, and stomach, respectively, at 30 minutes after oral administration of 4mg/kg rifampicin containing 100-200 µCi of activity. The highest percentage of radio-activity was found in the stomach because of the oral administration of labeled rifampicin, which acts as the source organ. At 4 and 8 h, the percentage of activity in the lungs starts to decrease. Subsequently, the radio-activity in the kidneys and liver starts to increase. The peak percentage of activity in the lungs was found at 30 min and decreased over 8 hours post oral administration of labeled rifampicin (Fig.5). Thus, attachment of99mTc to the rifampicin molecule does not affect the PK of rifampicin.