Urine radioactivity

Blood plasma levels in mg/kg fresh weight (FW) were 0.4 after 4 h and 0.18 after 72 h forfamoxon, these values were not detectable at 4 h and 0.05 at 72 h. Plasma and urine radioactivity levels reached maxima after 24 h... 

Gault, H. Kalra, J. Ahmed, M. Kepkay, D. Longerich, L. Barrowman, J. Influence of gastric pH on digoxin biotransformation. II. Ebctractable urineuy metabolites. Clin.Pharmacol.Ther, 1981, 29, 181-190 [urine radioactivity detection tritium labeled]... 

The experimental data of plasma and urine radioactivities were analyzed by the non-compartmental approach (Rescigno and Gurpide, 1973), as described in details previously (Bianchi et al., 1979). The formulas utilized in this approach allow to determine the following parameters of uric acid kinetics total metabolic clearance rate (MCR), mean residence time of the tracer, total distribution volume (TDV, plasma equivalent), fractional catabolic rate (FCR, relative to TDV), and clearance rate of C-uric acid via the renal route (MCR] ). The total turnover rate (TR) and the total pool of exchangeable uric acid are then obtained as the product of, respectively MCR or TDV by the plasma urate concentration. The extrarenal disposal of uric acid (bacterial uricolysis in the gut, skin desquamation) is determined as the difference between the total metabolic clearance rate and the clearance rate of uric acid through the kidney route. 

The metabohc rate of poly(ester—amide) where x = Q has been studied in rats using carbon-14 labeled polymer. This study indicates that polymer degradation occurs as a result of hydrolysis of the ester linkages whereas the amide linkages remain relatively stable in vivo. Most of the radioactivity is excreted by urine in the form of unchanged amidediol monomer, the polymer hydrolysis product (51). 

Metabolism. Absorption, distribution, metaboHsm, and excretion of thioglycolic acid have been reviewed (20). In summary,. -thioglycolic acid was absorbed significantly after appHcation to the skin of rabbits. After intravenous injection, the greatest counts of radioactivity were found in the kidneys, lungs, and spleen of monkey and in the small intestine and kidneys of rat. Most of the radioactivity was rapidly excreted in the urine in the form of inorganic sulfate and neutral sulfur. 

Plasma levels of 3—5 p.g/mL are obtained two hours after adraiinistration of 200 mg ketoconazole. No accumulation in the bloodstream was noted after a 30-wk treatment with this dose. The half-life is approximately eight hours. When ketoconazole is taken with meals, higher plasma levels are obtained. Distribution studies using radioactive ketoconazole in rats show radioactivity mainly in the Hver and the connective tissue. Radioactivity is also present in the subcutaneous tissue and the sebaceous glands. After one dose of 200 mg in humans, ketoconazole is found in urine, saUva, sebum, and cenimen. Like miconazole, the mode of action is based on inhibition of the cytochrome P-450 dependent biosynthesis of ergosterol. This results in disturbed membrane permeabiUty and membrane-bound enzymes (8,10,23,25). 

EoUowing po administration moricizine is completely absorbed from the GI tract. The dmg undergoes considerable first-pass hepatic metabolism so that only 30—40% of the dose is bioavailable. Moricizine is extensively (95%) bound to plasma protein, mainly albumin and a -acid glycoprotein. The time to peak plasma concentrations is 0.42—3.90 h. Therapeutic concentrations are 0.06—3.00 ]l/niL. Using radiolabeled moricizine, more than 30 metabolites have been noted but only 12 have been identified. Eight appear in urine. The sulfoxide metabolite is equipotent to the parent compound as an antiarrhythmic. Elimination half-life is 2—6 h for the unchanged dmg and known metabolites, and 84 h for total radioactivity of the labeled dmg (1,2). 

Perminks et al. (1987) reported that 80% of a single oral dose of dioctyltin dichloride at 2 mg/kg body weight was excreted in the faeces within 2 days. After 3 days, excretion of radioactivity followed first-order kinetics, with a half-life of 8.9 days. After intravenous administration, 66% of the radioactivity was excreted in the faeces, and a half-life value of 8.3 days was obtained, roughly similar to that of oral administration. Percentages of radioactivity excreted in the urine were 11% and 22% following intravenous and oral dosing, respectively. 

In a study of pregnant rats that were exposed to radiolabeled methyl parathion by single dermal application, half-life elimination rate constants for various tissues ranged from 0.04 to 0.07 hour, highest values noted in plasma, kidneys, and fetus. Of the applied radioactivity, 14% was recovered in the urine in the first hour postapplication. By the end of the 96-hour study, 91% of the applied dose had been recovered in the urine. Fecal excretion accounted for only 3% of the administered dose (Abu-Qare et al. 2000). 

Radioactivity Analysis. Samples of urine, feces, and tissues were combusted to COo and analyzed for radioactivity (5). By using this method the recovery of radioactivity from samples spiked with C was 95 dt 5%. To determine the radioactivity expired as CO2, 5-ml aliquots of the solution used to trap the CO2 were added to 15 ml of a scintillation counting solution containing 4 grams 2,5-diphenyloxazole (PPO) and 0.1 grams l,4-bis-2(5-phenyloxazolyl)-benzene (POPOP) per liter of 1 1 toluene 2-methoxyethanol. Samples were counted for radioactivity in a Nuclear Chicago Mark II liquid scintillation counter. Counting eflSciency was corrected by the internal standard technique. 

The percentage of the total dose of radioactivity excreted daily in the feces, urine, or expired air over a 21-day period following a single oral dose of TCDD- C is shown in Figure 2. Approximately 30% of the... 

Figure 2. Thin-layer radiochromatogram of urine (100 il) from rats injected with labeled PbTx-3. TLC plates were developed in two sequential solvent systems chloroform ethyl acetate ethanol (50 25 25 80 10 10). Radioactive zones were scraped and counted in a liquid scintillation counter. Native PbTx-3 runs at 13 cm.

The radioactivity in urine, feces, and expired breath was evaluated following exposure of mice and rats to [ " C]-radiolabelled trichloroethylene (Stott et al. 1982). In mice, 75% of the radioactivity was excreted in the... 

Metabolism of NHEX- C in the rat results in dose dependent formation of C02> with 45% exhaled after a dose of 8 mg/kg NHEX but only 4% after 576 mg/kg (17). Similar results were obtained for NPYR and nitrosoheptamethyleneimine. At doses of 8-12 mg/kg NHEX, 33-37% of the radioactivity was excreted in the urine (17, 52). Urinary metabolites of NHEX were e-caprolactam, e-amino-caproic acid, and 6-aminocaprohydroxamic acid (52). The formation of 6-caprolactam is analogous to results with NPYR and NNN, in which 2-pyrrolidinone and norcotinine were observed as urinary metabolites. Caprolactam did not originate from hexamethylene-imine, a product of denitrosation. 

The area under the PCP concentration-time curve (AUC) from the time of antibody administration to the last measured concentration (Cn) was determined by the trapezoidal rule. The remaining area from Cn to time infinity was calculated by dividing Cn by the terminal elimination rate constant. By using dose, AUC, and the terminal elimination rate constant, we were able to calculate the terminal elimination half-life, systemic clearance, and the volume of distribution. Renal clearance was determined from the total amount of PCP appearing in the urine, divided by AUC. Unbound clearances were calculated based on unbound concentrations of PCP. The control values are from studies performed in our laboratory on dogs administered similar radioactive doses (i.e., 2.4 to 6.5 pg of PCP) (Woodworth et al., in press). Only one of the dogs (dog C) was used in both studies. 

Information on the excretion of americium after dermal exposure in humans or animals is extremely limited. Some qualitative information is available from an accidental exposure in which a worker received facial wounds from projectile debris and nitric acid during an explosion of a vessel containing 241 Am (McMurray 1983). The subject also inhaled 241Am released to the air as dust and nitric acid aerosols, which was evident from external chest measurements of internal radioactivity thus, excretion estimates reflect combined inhalation, dermal, and wound penetration exposures (Palmer et al. 1983). Measurements of cumulative fecal and urinary excretion of241 Am during the first years after the accident, and periodic measurements made from day 10 to 11 years post accident indicated a fecal urine excretion ratio of approximately 0.2-0.3, although the ratio was approximately 1 on day 3 post accident (Breitenstein and... 

In rats given 66 or 660 mg/kg diisopropyl methylphosphonate, peak radioactivity in the blood was at 2-3 hours in both sexes at both doses however, radioactivity was still detectable in the blood 24 hours postadministration in the 66-mg/kg group (Weiss et al. 1994). After intravenous administration of 66 mg/kg, the elimination half-life of diisopropyl methylphosphonate was estimated at 45 minutes in males and 250 minutes in females the rate of excretion was greater in males than in females. Urine and feces together accounted for 86-97% of administered radioactivity in males and 57-62% in females. 

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