Kinetics eliminations

The mean residence time (MRT) gives one parameter for the multi-exponential elimination kinetics with more than one half-life. 

Rolinski B, Bogner JR, Sadri 1, Wintergerst U, Goebel FD (1997) Absorption and elimination kinetics of zidovudine in the cerebrospinal fluid in HIV-1-infected patients. J Acquir Immune Defic Syndr Hum Retrovirol 15(3) 192-197... 

Roy S, O Hanninen (1994) Pentachlorophenol uptake/elimination kinetics and metabolism in an aquatic plant Eichhornia crassipes. Environ Toxicol Chem 13 763-773. 

Our pharmacokinetic data indicate that detectable PCP levels may remain in the urine for 4 to 5 weeks after the last use, similar to previous reports (Khajawall and Simpson 1983). The observed elimination kinetics were equally consistent with a one- or two-compartment model, but methodological problems with our data make... 

Once a semilog plasma concentration versus time plot begins to follow simple first-order elimination kinetics, the remaining AUC can be calculated in one step using Eq. (45). 

R. Miller, R. Roberts, and L. Fischer, Acetaminophen elimination kinetics in neonates, children, and adults, Clin. Pharmacol. Ther, 19, 284 (1976). 

Hryhirczuk DO, Rabinowitz RB, Hessl SM, et al. 1985. Elimination kinetics of blood lead in workers with chronic lead intoxication. Am J Ind Med 8 33-42. 

Schmeider, P., D. Lothenbach, J. Tietge, R. Erickson, and R. Johnson. 1995. [3H]-2,3,7,8-TCDD uptake and elimination kinetics of medaka (Oryzias latipes). Environ. Toxicol. Chem. 14 1735-1743. 

Schrap, S.M. and A. Opperhuizen. 1988. Elimination kinetics of two unmetabolized polychlorinated biphenyls in Poecilla reticulata after dietary exposure. Bull. Environ. Contam. Toxicol. 40 381-388. 

Lipniak-Gawlik, M. 1998. Effect of polycyclic aromatic hydrocarbons on the elimination kinetics of pyrene and the urinary excretion profile of 1-hydroxypyrene in the rat. Jour. Toxicol. Environ. Health 55A 503-516. 

Phillips (1980) andPhillips and Rainbow (1993) have stated that each species of aquatic BMO exhibits unique uptake and elimination kinetics for a particular HOC. The ramification of this statement is revealed in the following simple one-compartment model, which is often used for the determination of steady-state BCFs and Ks s. 

Bmggeman, W.A. Martron, L.B.J.M. Kooiman, D. Hutizinger, O. 1981, Accumulation and elimination kinetics of di- tri- and tetrachlorobiphenyls in goldfish after dietary and aqueous exposure. Chemosphere 10 811—832. 

Commercial samples containing approximately 400 mg of ephedra per capsule yield roughly 5 mg of ephedrine, 1 mg of pseudoephedrine, and less than 1 mg of methylephedrine (White et al. 1997). For a dose of four capsules, yielding approximately 20 mg of ephedrine, the elimination half-life is 5.2 hours. The time to reach maxium concentration is 3.9 hours. Compared to pure ephedrine tablets, the elimination kinetics of ephedra are comparable. However, ephedra showed somewhat different absorption kinetics (e.g., lag time, area under the concentration-time curve, and maximum plasma concentration). So, ephedra tablets may vary from pure ephedrine in the onset of action, but the durations of action are grossly equivalent. 

Dempsey D, Jacob P, 3rd, Benowitz NL (2000) Nicotine metabolism and elimination kinetics in newborns, din Pharmacol Ther 67(5) 458 65... 

Thus, in critically ill patients where catheters are conventionally inserted for diagnostic or therapeutic interventions, incorporation of the appropriate fiber optics to commercial catheters would enable the monitoring of hepatic function continuously and simultaneously with other medical interventions. Previous studies by the absorption method also found a close correlation between invasive and noninvasive ICG plasma elimination kinetics [157,160]. 

B. Changes in elimination kinetics in the course of drug therapy... 

Labetalol is almost completely absorbed from the gastrointestinal tract. However, it is subject to considerable first-pass metabolism, which occurs in both the gastrointestinal tract and the liver, so that only about 25% of an administered dose reaches the systemic circulation. While traces of unchanged labetalol are recovered in the urine, most of the drug is metabolized to inactive glucuronide conjugates. The plasma half-life of labetalol is 6 to 8 hours, and the elimination kinetics are essentially unchanged in patients with impaired renal failure. 

Miceli JN, Marks BH. 1981. Tissue distribution and elimination kinetics of polybrominated biphenyls (PBB) from rat tissue. Toxicol Lett 9 315-320. 

Saturation of the processes involved in the elimination of a foreign compound from the plasma, such as metabolism and excretion, may also have toxicological consequences. Thus, ethanol exhibits zero-order elimination kinetics at readily attainable plasma concentrations, because the metabolism is readily saturated. Therefore, once these plasma concentrations have been attained, the rate of elimination from the plasma is constant. Increasing the dosage of ethanol leads to accumulation and the well-known toxic effects. 

Drug Distribution. After administration, a drug may be distributed either generally or selectively in the body. The distribution pattern depends on many factors, including the pattern and time-course of blood (low, diffusion of drugs into tissues, binding of drugs to plasma proteins and cellular compartments, and elimination kinetics and mechanisms. 

Zero-order elimination kinetics are described by the following equation 1... 

The HPLC determination of CAP and TAP residues in gamebird (pheasant, mallard, and quail) was published (131). The drugs were extracted by LLE from the homogenized tissues (muscle, liver) by water, and the extracts were purified by subsequent partition with a ChemElut cartridge. The drug was eluted with ethyl acetate and the eluate after the evaporation was mixed with water and extracted with toluene. The aqueous phase was injected into an HPLC system. The recoveries were 67% for CAP and 72% for TAP. The purity of analyzed compounds was verified by DAD. The elimination kinetics of CAP and TAP from the quail tissues were also evaluated. 

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