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Biomedical subjects

R N Berk

Publications and source records attributed to R N Berk.

At least 109 records · Page 6Linked to original sources
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The biliary and urinary excretion and the choleretic effect of ioglycamide in dogs.

The biliary and urinary excretion and the choleretic effect of ioglycamide were studied in unanesthetized bile fistula dogs using stepwise increasing infusion rates to obtain multiple steady states. The results are compared with data from previously reported experiments in the same animals using iodoxamate and iodipamide. The rate of biliary excretion and the choleretic effect of ioglycamide are similar to those of iodipamide and iodoxamate. Like iodipamide and iodoxamate, the relation between infusion rate or plasma concentration and biliary excretion or concentration of ioglycamide are hyperbolic and can be fitted to saturation kinetics. Quantitatively, the excretion of ioglycamide and iodipamide are virtually identical. However, for any equimolar infusion rate or plasma concentration, more iodoxamate than ioglycamide is excreted in the bile. Despite the greater biliary excretion of iodoxamate, the maximum biliary concentration of ioglycamide, iodipamide, and iodoxamate is the same at low basal bile flow because the choleretic effects of the three compounds are equal. The data suggest that, theoretically, with any equimolar dose ioglycamide will be identical to iodipamide as a contrast material for intravenous cholangiography, but that iodoxamate may be superior to ioglycamide because more iodoxamate is excreted in the bile. This advantage of iodoxamate might become apparent clinically in patients with high basal bile flow or if smaller doses of the contrast material are used. However, at the presently recommended doses of the two compounds, it is unlikely that the use of ioglycamide for intravenous cholangiography will be any different than iodoxamate.

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PubMedDate not supplied

The biliary and urinary excretion of sodium tyropanoate and sodium ipodate in dogs: pharmacokinetics, influence of bile salts and choleretic effects with comparison to iopanoic acid.

The biliary and urinary excretion of sodium tyropanoate (Bilopaque) and sodium ipodate (Oragrafin) were studied in unanesthetized bile-fistula dogs using stepwise, increasing, intravenous infusions of the contrast materials. A constant intravenous infusion of sodium taurocholate was administered at the rate of either 0.5 or 2.0 mu moles per min per kg throughout each experiment. The biliary excretion of sodium tyropanoate or sodium ipodate was not effected by the rate of sodium taurocholate infusion. The maximum rate of biliary excretion of sodium ipodate was significantly greater than that of sodium tyropanoate with the low taurocholate infusion, but there was no significant difference between the two with the high taurocholate infusion. With the low taurocholate infusion the maximum biliary excretion rate of sodium tyropanoate (0.956 mu moles per min per kg) and sodium ipodate (1.472 mu moles per min per kg) were significantly greater than the maximum biliary excretion of iopanoic acid (Telepaque) (0.671 mu moles per min per kg). With the high taurocholate infusion the maximum biliary excretion rates of the three contrast agents were not statistically different. Both sodium tyropanoate and sodium ipodate produced an increase in canalicular bile flow (8-11 ml per millimole). These data suggest that in clinical cholecystography sodium tyropanoate and sodium ipodate are not excreted in bile more rapidly than iopanoic acid, except when the rate of biliary excretion of bile salts is low; that is, except in patients who are fasting or those who are on a fat-free diet.

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Saturation kinetics of iocetamic acid: Evaluation of indirect pharmacokinetic techniques and comparison with iopanoic acid.

The biliary excretion of two oral cholecystographic contrast agents, iocetamic acid and iopanoic acid, were compared during low and high taurocholate infusion rates. The pharmacokinetics of these compounds after intravenous infusion were studied in bile-fistula dogs using both indirect and direct pharmacokinetic techniques. The indirect multiple infusion technique, corrected for urinary excretion, provides a reliable estimate of the maximum biliary excretion rates of either contrast agent without necessitating the sampling of biliary output. The results indicate that taurocholate facilitates the biliary excretion of both agents. At both taurocholate infusion rates studied, the maximum biliary excretion rate of iocetamic acid is greater than that of iopanoic acid.

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The present status of imaging of the gallbladder.

Oral cholecystography is still the basic modality for the diagnosis of gallbladder disease. Now, for the first time since the introduction of this procedure in 1924, this status is being challenged by another diagnostic technique, ultrasonography of the gall bladder. Ultrasound studies have major advantages over conventional cholecystography. These are sufficiently important that it can be safely predicted that ultrasonography will eventually become the primary diagnostic tool for evaluating the gallbladder. Just as the use of colonoscopy has provoked a new analysis of the barium enema examination in the evaluation of the colon, the introduction of ultrasound examination of the gallbladder has revealed the fact that false-negative oral cholecystograms are not rare. Before ultrasonography this information was unobtainable, because of the surgeon's proper reluctance to perform a cholecystectomy in patients with normal oral cholecystograms. Indeed, the availability of an accurate alternate diagnostic procedure has stimulated a reevaluation of other difficulties associated with oral cholecystography. These include problems involved with non-visualization and impaired visualization of the gallbladder after a single dose of contrast material, misunderstandings concerning the uses of oral cholecystography compared to those for intravenous cholangiography and uncertainty regarding the value of cholecystokinin cholecystography in the diagnosis of acalculous cholecystitis. Knowledge of the pharmacokinetics of the oral cholecystographic contrast agents has been long overdue, considering the extensive use of these compounds in clinical practice for more than 50 years. However, information on this subject has finally reached a stage where the data can be applied to ensure that cholecystography is done with maximun efficiency and safety and with the least radiation exposure. The purpose of this report is to review the problems involved with imaging of the gallbladder by oral cholecystography and to discuss the indications, interpretation and accuracy of gallbladder imaging with ultrasonography. Data concerning the use of computerized tomography for evaluation of the gallbladder are still preliminary but are discussed.

Administration, Oral↗
PubMedDate not supplied

Changes in bile flow and composition induced by radiographic contrast materials.

The hepatic excretion of radiographic contrast materials has a major impact on the composition and volume of bile. One obvious effect is the presence of the contrast agent in bile at a concentration that is determined by the rate of hepatic excretion, the rate of basal bile flow, and the rate of bile flow induced by the biliary excretion of the contrast agent. The magnitude of the choleretic response associated with the biliary transfer of contrast materials varies over a wide range. Iopanoic acid does not increase bile flow, whole RCK-136, an experimental contrast material that is similar to iopanoic acid chemically (both are triiodophenyl alkanoates), is a potent choleretic, generating 44 microliter of bile for each mumol excreted into bile. In distinction, the contrast materials in another chemical class, the dimers of triiodobenzoic acid, increase bile flow, but over a narrow range (20-25 microliter/mumol). The changes in bile flow and composition accompanying the administration of iodoxamate, one of the compounds of the dimer type, were compared to the choleresis induced by taurocholate. The additional bile flow was canalicular in origin in both instances, but the electrolyte composition of the bile was different. Bicarbonate concentration in the iodoxamate-induced increment of bile was nearly twice the concentration of bicarbonate in bile stimulated by taurocholate (52.3 and 25.3 mEq/1, respectively). This suggests a canalicular mechanism for iodoxamate-stimulated bicarbonate entry into the bile. The characteristics of bile induced by iodoxamate were also compared to bile associated with a variety of other choleretic agents, including diethyl maleate, DBcAMP, SC2644, and secretin. Only SC2644 stimulated canalicular bile flow with a high bicarbonate concentration similar to iodoxamate.

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PubMedDate not supplied

The potential of iosulamide meglumine as a contrast material for intravenous cholangiography: an experimental study in dogs.

Because of relatively low acute toxicity, iosulamide meglumine has been recommended as an improved contrast material for intravenous cholangiography. It has been postulated that high doses of the compound could be given safely with the expectation of achieving greater biliary excretion and improved opacification of the biliary tree. Experiments performed in dogs show that higher rates of infusion of iosulamide result in greater urinary elimination without additional biliary excretion. Consequently, iosulamide is unlikely to have any special advantage as a contrast agent.

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PubMedDate not supplied

Does glucagon enhance opacification of the bile ducts during intravenous cholangiography? An experimental study in dogs.

To determine the rational for the ability of glucagon to enhance opacification of the bile ducts during intravenous cholangiography, which has been claimed in recent clinical reports, experiments were performed in dogs which had had Thomas cannulas inserted. A constant step-wise infusion of iodipamide was administered with or without a bolus injection and constant infusion of glucagon. At every infusion rate of iodipamide the biliary concentration of the contrast agent was less when glucagon was administered. Glucagon caused a choleresis, but had no effect on the rate of excretion of iodipamide. It is concluded that the theory that glucagon is of value to improve opacification of the bile ducts during intravenous cholangiography is unlikely to be confirmed by further clinical trials.

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