Biological half-hfe

Pharmacokinetics Pharmacokinetic studies found that the mean biologic half-life of Kogenate (rAHF) was about 13 hours. The mean biologic half-hfe of plasma-derived AHF in the same individuals was 13.9 hours. In a comparative pharmacokinetic study, Kogenate FS was shown to be similar to its predecessor product Kogenate. 

Advantages of LMWHs over UFH include (1) more predictable anticoagulation dose response (2) improved SC bioavailabflity (3) dose-independent clearance (4) longer biologic half-hfe (5) lower incidence of thrombocytopenia and (6) less need for routine laboratory monitoring. 

Cadmium is accumulated extraordinarily strongly in the human body. In newborn infants, the total cadmium amount is usually approximately 1 pg and by the 50th year of life the total amounts may be as high as 20 to 30 mg. In man, the value of the cadmium biological half-hfe ranges between 10 and 30 years. The kidneys, liver, lung and testes are the critical organs... 

Different concentrations of various metals are observed between open and nearly closed bayg232 effective half-hfe of nOmAg (equation 55) in squids after Chernobyl is 7 (i/2)eff = 130 days, in oysters after the Chernobyl accident r(i/2)eff = 140 days and in oysters after the 26th Chinese test r(i/2)eff = 160 days. The r(i/2)eff value is shorter than the physical half-hfe, Tphys = 249.76 days. Taking T a = 150 days for D9 Ag in oysters, we find that T = 375 days. This number probably reflects the half-residence time of ii° Ag in the sea water rather than the biological half-hfe in the oysters. The 7 (i/2)eff values of ii° Ag for oysters and squids are similar. The specific radioactivity of l° Ag for oysters was found to be 0.026 0.008 Bq/mg silver at the open Japanese coast which compares with value of 0.021 0.005 Bq/mg silver for squid in the Pacific Ocean. This coincidence suggests the similar behaviour of i0 Ag in Pacific Ocean oysters and squids and also a uniform distribuhon of i° Ag in the Pacific Ocean water. Thus the present levels of ii° Ag or lo m g found in the above environmental studies do not ensue a health hazard. The ICRP recommended the value of 2 x 10 Bq for llOmAg us an annual hmit of intake. 

The biological half-hfe of mercury in the blood is approximately three days, following an erqrosure but the mercury bound to body tissues clears much more slowly with a half-life of about 90 days. Thus the end of an exposure wiU have long lasting effects. The levels in tissue will not fall below 10% of the peak level until somewhat more than four haU-hves have passed. 

The relatively long biological half-hfe of radiolabeled annexin V analogs and prolonged time between i.v. administration of the radiotracer and imaging... 

Leete E (1983) Biosynthesis and metabohsm of the tobacco alkaloids. In Pelletier SW (ed) Alkaloids chemical and biological perspectives, WUey, New York, pp 85-152 Leong JW, Dore ND, SheUey K, Holt EJ, Laing lA, Palmer LJ, LeSouef PN (1998) The elimination half-hfe of urinary cotinine in children of tobacco-smoking mothers, Pulm Pharmacol Ther ll(4) 287-290... 

Storage of spent nuclear fuel poses a major problem because the fission products are extremely radioactive. It is estimated that 10 half-lives are required for their radioactivity to reach levels acceptable for biological exposure. Based on the 28.8-yr half-life of strontium-90, one of the longer-Hved and most dangerous of the products, the wastes must be stored for nearly 300 yr. Plutonium-239 is one of the by-products present in spent fuel elements. It is formed by absorption of a neutron by uranium-238, followed by two successive beta emissions. (Remember that most of the uranium in the fuel elements is uranium-238.) If the elements are reprocessed, the plutonium-239 is largely recovered because it can be used as a nuclear fuel. However, if the plutonium is not removed, spent elements must be stored for a very long time because plutonium-239 has a half-hfe of 24,000 yr. 

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