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Applied Radiation and Isotopes :... Dec 2022The half-lives of Sc and Sc were measured by following their decay rate using several measurement systems: two ionization chambers and three γ-spectrometry detectors...
The half-lives of Sc and Sc were measured by following their decay rate using several measurement systems: two ionization chambers and three γ-spectrometry detectors with digital and/or analogue electronics. For Sc, the result was the combination of seven half-life values giving a result of 4.042(7) h, which agrees with the last reported value of 4.042(3) h and confirms the near to 2% deviation from the recommended half-life of 3.97(4) h. Scandium-44 is present as an impurity in the production of Sc by cyclotron proton irradiation. Its half-life was determined by measurements performed a few days after End of Bomardment (EoB), so that the Sc decayed down to a negligible level. Seven measurements were combined to obtain an average of 58.7(3) h, which is in agreement with the recommended value of 58.6(1) h.
Topics: Half-Life; Scandium; Cyclotrons
PubMed: 36228535
DOI: 10.1016/j.apradiso.2022.110507 -
Turkish Journal of Haematology :... Aug 2019Despite effective factor replacement and various treatment schedules, there remain several challenges and unmet needs in the prophylactic treatment of hemophilia... (Review)
Review
Despite effective factor replacement and various treatment schedules, there remain several challenges and unmet needs in the prophylactic treatment of hemophilia limiting its adoption and thereby posing an increased risk of spontaneous bleeding. In this regard, extended half-life (EHL) recombinant factor VIII (rFVIII) and factor IX (rFIX) products promise optimal prophylaxis by decreasing the dose frequency, increasing the compliance, and improving the quality of life without compromising safety and efficacy. EHL products might lead to higher trough levels without increasing infusion frequency, or could facilitate the ability to maintain trough levels while reducing infusion frequency. This paper aims to provide a comprehensive review of the rationale for developing EHL coagulation factors and their utility in the management of hemophilia, with special emphasis on optimal techniques for half-life extension and criteria for defining EHL coagulation factors, as well as indications, efficacy, and safety issues of the currently available EHL-rFVIII and EHL-rFIX products. Potential impacts of these factors on quality of life, health economics, and immune tolerance treatment will also be discussed alongside the challenges in pharmacokinetic-driven prophylaxis and difficulties in monitoring the EHL products with laboratory assays.
Topics: Blood Coagulation Factors; Half-Life; Hemophilia A; Quality of Life
PubMed: 31088040
DOI: 10.4274/tjh.galenos.2019.2018.0393 -
Journal of Veterinary Pharmacology and... Dec 2004Terminal plasma half-life is the time required to divide the plasma concentration by two after reaching pseudo-equilibrium, and not the time required to eliminate half... (Review)
Review
Terminal plasma half-life is the time required to divide the plasma concentration by two after reaching pseudo-equilibrium, and not the time required to eliminate half the administered dose. When the process of absorption is not a limiting factor, half-life is a hybrid parameter controlled by plasma clearance and extent of distribution. In contrast, when the process of absorption is a limiting factor, the terminal half-life reflects rate and extent of absorption and not the elimination process (flip-flop pharmacokinetics). The terminal half-life is especially relevant to multiple dosing regimens, because it controls the degree of drug accumulation, concentration fluctuations and the time taken to reach equilibrium.
Topics: Animals; Half-Life; Models, Animal; Models, Biological; Plasma; Veterinary Drugs
PubMed: 15601438
DOI: 10.1111/j.1365-2885.2004.00600.x -
Applied Radiation and Isotopes :... Dec 2022Terbium-155 has been identified for its potential for single-photon emission computed tomography (SPECT) in nuclear medicine. For activity measurements, an accurate and...
Terbium-155 has been identified for its potential for single-photon emission computed tomography (SPECT) in nuclear medicine. For activity measurements, an accurate and precise half-life of this radionuclide is required. However, the currently evaluated half-life of 5.32(6) d with a relative standard uncertainty of 1.1% determines the precision possible. Limited literature for the half-life measurements of this radionuclide is available and all reported investigations are prior to 1970. Further measurements are therefore needed to confirm the accuracy and improve the precision of the half-life for its use in the clinical setting. Two samples produced and mass separated at the CERN-MEDICIS facility have been measured at the National Physical Laboratory by two independent techniques: liquid scintillation counting and high-purity germanium gamma-ray spectrometry. A half-life of 5.2346(36) d has been determined from the weighted mean of the half-lives determined by the two techniques. The half-life reported in this work has shown a relative difference of 1.6% to the currently evaluated half-life and has vastly improved the precision.
Topics: Half-Life; Radioisotopes; Tomography, Emission-Computed, Single-Photon; Spectrometry, Gamma; Nuclear Medicine
PubMed: 36209648
DOI: 10.1016/j.apradiso.2022.110480 -
The Journal of Clinical Psychiatry Jul 2022The half-life of a drug is most commonly defined as the time taken for the plasma or blood level of the drug to fall by half. Elimination half-life, pharmacologic...
The half-life of a drug is most commonly defined as the time taken for the plasma or blood level of the drug to fall by half. Elimination half-life, pharmacologic half-life, and biologic half-life are interchangeably used most commonly to describe the half-life of drugs that follow first-order or linear pharmacokinetics; that is, in single-compartment models, where the fall in blood level is proportionate to the concentration of the drug in blood. In 2 compartment models, where the drug equilibrates between blood and (for example) adipose tissue, during elimination there is a sharp initial fall in blood levels followed by a gradual subsequent fall; when drugs display this biphasic elimination pattern, the half-life corresponding to the second phase is what is clinically relevant, and this half-life is known as the terminal half-life. Half-life is influenced by drug distribution, drug metabolism, and drug excretion, each of which can be influenced by many factors such as age, use of concurrent medications, and presence of liver or renal disease. In order to maintain uniform blood levels and reduce the adverse effect risk, drugs with short half-lives need to be dosed more frequently. Drugs with short half-lives are more likely to be associated with withdrawal or discontinuation syndromes. The duration of action of a drug, time to steady state levels, and time to washout are each influenced by the value of the drug half-life. All these terms and concepts are defined and explained with the help of clinically relevant examples. Mental health care professionals who prescribe to patients need to know the half-lives of the drugs that they prescribe, the half-lives of active metabolites, if any, how these half-lives may differ with individual patient characteristics, and how to use this knowledge to prescribe to best advantage.
Topics: Half-Life; Humans; Metabolic Clearance Rate; Psychopharmacology
PubMed: 35900254
DOI: 10.4088/JCP.22f14584 -
Applied Radiation and Isotopes :... Apr 2022There is significant interest in the use of terbium radioisotopes for applications in cancer therapy and diagnosis. Of these, Tb, as a medium energy beta-emitter, is...
There is significant interest in the use of terbium radioisotopes for applications in cancer therapy and diagnosis. Of these, Tb, as a medium energy beta-emitter, is being investigated as a potential alternative to Lu. The relatively high proportion of conversion electron and Auger electron emissions per decay make Tb an attractive targeted therapeutic. As a product of nuclear fission, Tb is also of importance to nuclear forensics. The standard uncertainty of the current evaluated half-life of 6.89(2) d contributes significantly to the standard uncertainty of any decay corrected activity determination made. Furthermore, the accuracy of this evaluated half-life has been called into question by measurements reported in 2020 at the Institute of Radiation Physics (IRA), Switzerland, who reported a half-life of 6.953(2) d. In the current work, the half-life of the Tb ground state decay has been measured at three independent laboratories located in the United Kingdom and the United States of America for a total of six determinations using three independent measurement techniques; gamma-ray spectrometry, ionisation chamber measurement and liquid scintillation counting. The half-life determined for Tb of 6.9637(29) d confirms the observed 1% relative increase observed by IRA, though the reported half-lives in this work and at IRA are significantly different (ζ-score = 3.1).
Topics: Half-Life; Radioisotopes; Radiopharmaceuticals; Terbium
PubMed: 35158282
DOI: 10.1016/j.apradiso.2022.110140 -
Expert Opinion on Drug Discovery Mar 2019The PK optimization of drug candidates is one of the most resource-intensive tasks in pharmaceutical research and development. With the increasing availability of in... (Review)
Review
The PK optimization of drug candidates is one of the most resource-intensive tasks in pharmaceutical research and development. With the increasing availability of in silico, in vitro and mechanistic in vivo ADME models, drug discovery scientists have progressively learned to recognize common SAR patterns and engineer data-driven strategies to accelerate the resolution of ADME issues in lead optimization. Many of these strategies gravitate toward the concept of drug-likeness, which defines a number of optimal holistic physicochemical parameters (such as lipophilicity) that idealized oral drugs possess. Areas covered: Herein, the authors discuss the interplay of lipophilicity with in vitro and in vivo ADME data in order to refine existing thought around drug half-life optimization. Strategies to prolong the half-life of oral drugs via formulation are beyond the scope of this review. Expert opinion: Optimizing active properties such as potency, selectivity, and intrinsic metabolic clearance is an unambiguously beneficial strategy for small molecules within or beyond the Lipinski rule of five chemical space. The data that we present in this work suggests that emphasis should be primarily placed on optimizing active properties such as potency, selectivity, and metabolic stability.
Topics: Computer Simulation; Drug Discovery; Half-Life; Humans; Models, Biological; Pharmaceutical Preparations; Structure-Activity Relationship
PubMed: 30675823
DOI: 10.1080/17460441.2019.1569625 -
Environmental Science and Pollution... Jun 2023Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is primarily transmitted from person to person through respiratory droplets and aerosols. It is also...
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is primarily transmitted from person to person through respiratory droplets and aerosols. It is also possible for the virus to be transmitted indirectly through environmental contamination. The likelihood of environmental transmission depends on several factors, including the survival time of the virus in respiratory secretions. However, the stability of SARS-CoV-2 in respiratory secretions has not been investigated. In this study, we compared the half-life of the SARS-CoV-2 antigen in respiratory secretion under different conditions. We applied respiratory secretion (5 µL) to glass slides, air-dried the slides for 1 h, and kept them at 24 °C or 4 °C for 10 days. Respiratory secretions were also placed in test tubes (sealed to preserve moisture) and in normal saline for 10 days. The concentration of SARS-CoV-2 antigen in all samples was simultaneously measured using colloidal gold immunochromatography, and the half-life of the antigen was calculated. The half-life of the antigen in the wet (sealed tube) and saline samples at room temperature was 5.0 and 2.92 days, respectively. The half-life of the antigen in the air-dried sample at room temperature and at 4 °C was 2.93 and 11.4 days, respectively. The half-life was longer in respiratory secretions than that in normal saline. The half-life was also longer in respiratory secretions, at a lower temperature, and under wet conditions. Therefore, environmental transmission can also play a significant role in the spread of the virus. Robust prevention and control strategies could be developed based on the half-life of the antigen in respiratory secretions.
Topics: Humans; SARS-CoV-2; COVID-19; Half-Life; Saline Solution; Respiratory Aerosols and Droplets
PubMed: 37129805
DOI: 10.1007/s11356-023-27326-1 -
Health Physics Jul 1989Direct observation of the 218Po alpha-peak decay with a microcomputer-controlled alpha-spectrometer yielded a mean half-life value of 3.040 +/- 0.008 min, where the... (Review)
Review
Direct observation of the 218Po alpha-peak decay with a microcomputer-controlled alpha-spectrometer yielded a mean half-life value of 3.040 +/- 0.008 min, where the error quoted represents twice the standard deviation of the means from 38 separate decay measurements. The 1912 and 1924 218Po half-life measurements, which provided the 3.05-min value listed in nuclear tables for the past 60 y, are critically reviewed. Two more recent experiments, which yielded longer values of 3.11 min (Van Hise et al. 1982) and 3.093 min (Potapov and Soloshenkov 1986), are also discussed.
Topics: Half-Life; Polonium; Radioactivity; Radiometry; Radon; Spectrum Analysis
PubMed: 2663779
DOI: 10.1097/00004032-198907000-00015 -
Applied Radiation and Isotopes :... Aug 2022Half-life is one of the fundamental parameters to characterize the thermoluminescent (TL) response in ionizing radiation dosimetry. In general, there are two types of...
Half-life is one of the fundamental parameters to characterize the thermoluminescent (TL) response in ionizing radiation dosimetry. In general, there are two types of important half-lives to model the phenomenon of thermoluminescence (TL). The first type of half-life is the time required for the concentration of trapped charge carriers in a single trap to decrease to half its initial value; this type of half-life is generally denoted as τ. Experimentally, the loss of charge carriers and the corresponding half-life τ are not usually measured directly, but rather the intensity of the TL signal is measured at time t after the start of the experiment. The second type of half-life is the time required for the intensity of the TL to decay to half its initial value. This second type of half-life it is denoted by t. Results of calculating the t half-life of the glow peaks of gamma irradiated BeO are presented. Calculations were made using the expressions derived in previous papers. To make this, the kinetic parameters (order of kinetics, activation energy and frequency factor) were previously determined. Results obtained could be useful in practical situations encountered in medical physics dosimetry.
Topics: Beryllium; Gamma Rays; Half-Life; Thermoluminescent Dosimetry
PubMed: 35617892
DOI: 10.1016/j.apradiso.2022.110291