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Conflicting data have been reported concerning the optimum dose and rate of administration of iodipamide required to obtain maximum radiographic opacification of the biliary tree during intravenous cholangiography. Experiments were performed in dogs to determine the effect of plasma concentration on the excretion and concentration of iodipamide in the bile and urine during a steady state of infusion and excretion. The data indicate that a hyperbolic relation exists between the plasma concentration and both the biliary concentration and the total biliary excretion. A mathematical expression of these relations is presented. At low plasma concentrations, iodipamide was not excreted in the urine. However, at high plasma concentrations, urinary excretion increased sharply. It appears that a biliary concentration of iodipamide sufficient to achieve adequate radiographic visualization of the biliary tree can be obtained without significant renal excretion by constant infusion of iodipamide at an appropriate rate in dogs. Stepwise increase in the infusion rate until adequate radiographic visualization is obtained may be the best method for performing intravenous cholangiography to obtain visualization with the least amount of iodipamide in order to minimize toxicity.

The volume of distribution of diatrizoate and iodipamide in blood in relation to hematocrit and contrast concentration was measured using 125I-labeled compounds. In concentration obtained after intravenous injection, the percentage volume of distribution of both contrast media is 100 minus hematocrit, except for high hematocrit values, which may cause uneven distribution of contrast media in smaller concentrations. No evidence of intracellular penetration was obtained.

Iodipamide and iodoxamate were compared at equimolar clinical dosages in dogs with normal, incompletely obstructed and completely obstructed common bile ducts. Forty-eight experiments were performed under general anesthesia in six cholecystomized chronic bile fistula dogs. The peak biliary iodoxamate excretion rate, but not the peak bile iodoxamate concentration, was significantly higher with normal and incompletely obstructed common bile ducts. In complete obstruction, both a significantly higher total biliary iodoxamate excretion and concentration were obtained, but this was still insufficient for radiographic opacification by conventional technique. Lesser toxicity of iodoxamate is suggested by its significantly lower serum levels, its higher bile: urine excretion ratio and its faster compensatory urinary excretion in complete common bile duct obstruction. Iodoxamate appears on this evidence to be a better cholangiographic contrast agent than iodipamide.

1.A decrease in the plasma binding of iotroxamide was found in jaundiced people. 2. The decrease in binding was associated with an enhancement in renal excretion. 3. Iotroxamide consistently gave higher biliary iodine concentrations than ioglycamide.

The biliary excretion and choleretic effects of iodoxamate (Cholevue) and iodipamide (Cholografin) were compared in unanesthetized dogs with biliary fistulas in order to assess the potential of the two contrast agents for use in intravenous cholangiography. For any equimolar infusion rate, more iodoxamate was secreted in the bile than iodipamide was the same. At the constant basal bile flow maintained in these studies, there was no difference in the maximum biliary concentration of the two compounds. With the presently recommended doses, it is unlikely that iodoxamate will offer a striking improvement over iodipamide for intravenous cholangiography in patients with normal liver function.