Bile fistula study in rats

To investigate the rate and the extent of the excretion of the drug/metabolites with the bile. If required, the investigation can be supplemented to study the entero-hepatic circle. The bile fistula study becomes necessary when relevant parts of the administered radioactivity are eliminated fecally suggesting a considerable biliary excretion during the mass balance study in rats. 

Since the intravenous administration ensures the maximum exposure especially in case of anesthetized or preoperated animals, this route is often favored. 

Four healthy male anesthetized Sprague Dawley (or Wistar) rats weighing about 300 g (10-12 weeks old) and provided with a permanent bile fistula receive an intravenous dose (such as 5 mg/kg for instance into the tail vein, procedure see mass balance study in rats without the necessity to use the described tube for the animals). 

GB) or similar material (like flexible silicon 

The rats are fasted for about 4 h and are anesthetized with 80 mg/kg bw Ketamin plus 5 mg/kg Midazolam administered intravenously into the tail vein via an indwelling venous catheter. The amount corresponds to a volume of about 0.3 mL. Anesthesia is monitored by checking the reflexes and is maintained by repeat dosing of ketamine/midazolam. 

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