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Origin and Classification of Radiation
Published in Philip T. Underhill, Naturally Occurring Radioactive Material, 2018
Radionuclides deposited within the human body are usually considered to be eliminated from the body at a rate proportional to the amount of the radionuclide present, resulting in an exponential decrease in the amount of the material in the body. This process of elimination is analogous to the radioactive half-life and is termed the biological half-life (T1/2b). The biological half-life is the approximate time taken for an average adult human to eliminate one-half of a radioactive substance, by normal biological means only. This parameter is calculated independent of the radioactive properties of the substance and is determined strictly by the ability of the body to remove the particular element (e.g., radium, iodine, etc.).
Nuclear Terrorism
Published in Robert A. Burke, Counter-Terrorism for Emergency Responders, 2017
Rates at which radioactive isotopes are eliminated from the body are expressed as the biological half-life. That is the time it takes one-half of the material to be excreted or expelled from the body. During each additional half-life, an additional one-half of the material is eliminated. Not all isotopes are removed in an exponential fashion, but the biological half-life theory is accurate enough to be used with most soluble isotopes. Insoluble heavy metals such as plutonium will not be removed in this manner and will remain in the lungs and bone for a long period of time. Biological half-life depends on the body's ability to process water and remove it through the kidneys. This can take as long as 18 days or can occur in as little as 4 days. Removal rates of water from the body depends on the volume taken in, the state of hydration, and kidney function. Intakes of large amounts of water can accelerate the process. Another factor considered in the elimination of radioactive isotopes from the body is the radiological half-life of the isotope. The two terms factored together are expressed as the “effective half-life.” This relationship is expressed in the following equation: Effective half-life=Biological half-life×Radiological half-lifeBiological half-life+Radiological half-life
Chapter 6 Radioisotopes and Nuclear Medicine
Published in B H Brown, R H Smallwood, D C Barber, P V Lawford, D R Hose, Medical Physics and Biomedical Engineering, 2017
The clearance of a substance from the body is often described in terms of a biological half-life. This is given by (loge 2)/k and is the time taken for half the radioactivity to be cleared from the body. The term biological half-life is used since it is determined by biological processes rather than physical ones. It is additional to the physical decay of the tracer which must be corrected for before the biological half-life can be measured (see previous comments on p 166).
Cytotoxic profile study, DNA and protein binding activity of a new dinuclear nickel(II) thiocyanato complex
Published in Journal of Coordination Chemistry, 2022
Niladri Biswas, Sandeepta Saha, Barun Kumar Biswas, Manas Chowdhury, Ashikur Rahaman, Deba Prasad Mandal, Shamee Bhattacharjee, Ennio Zangrando, Ruma Roy Choudhury, Chirantan Roy Choudhury
The investigation of drugs binding with albumins has become an important research field in chemistry, life sciences, and clinical medicine [25]. Serum albumin (SA), being the most abundant protein in the blood circulatory system, plays important roles in the transport of drugs and metal ions throughout the blood system [26]. The structural homologue BSA and HSA albumins contain about 55% of the total amounts of plasma proteins and play an important role in the maintenance of the osmotic pressure and transport and metabolism of drugs [27, 28]. Thus, both these proteins have been attracting immense interest and are often chosen as target protein in the study of interaction with small molecules, and the amount of interacting drug with respect to the free species determines the drug’s pharmacological effects and also its biological half-life in the body [29].
An insight on topically applied formulations for management of various skin disorders
Published in Journal of Biomaterials Science, Polymer Edition, 2022
Amit K. Jain, Sakshi Jain, Mohammed A. S. Abourehab, Parul Mehta, Prashant Kesharwani
Topical formulations are those which are applied directly to an external body surface like either on the surface of eye, vagina, rectum or urethral lining. While dermatological on the other hand are those products which are applied only on the skin or scalp [6]. Topical formulations have various advantages vis-à-vis conventional route of delivery such as circumvent the first pass metabolism, gastrointestinal compatibility, selectivity to a particular site, improved patient compliance, hassle-free self-medication, etc. Topical route also allows the application of drug with short biological half-life and narrow therapeutic window [42]. In the formulation of an effective and efficient topical preparation consideration must be given to the intended purpose. This is directly related with the site of action and desired effect of the preparation. General illustration of mechanism of drug release is given in Figure 3.
A meticulous overview on drying-based (spray-, freeze-, and spray-freeze) particle engineering approaches for pharmaceutical technologies
Published in Drying Technology, 2021
Sagar Pardeshi, Mahesh More, Pritam Patil, Chandrakantsing Pardeshi, Prashant Deshmukh, Arun Mujumdar, Jitendra Naik
SR formulations are designed in a manner to achieve the prolonged therapeutic effect by continuously releasing the drug over an extended period of time after administration of a single dose. The matrix and membrane formers (matrix and reservoir system) are used as release controlling agents in SR formulation as discusses in the above section.[143,144] In the case of orally administered dosage forms, the period is measured in hours and critically depends on the residence time of the dosage form in the GI tract. The SR formulations avoid problems associated with narrow therapeutic index drugs, reduce dosing frequency, and improve patient compliance by avoiding systemic toxicity associated with more potent drugs. In addition, it helps to improve the bioavailability of drugs with short half-life in vivo.[145,146] The variable drug-blood level of multidosing conventional dosage form is reduced by SR formulations. The drawbacks of SR formulations include it does not permit prompt termination of the therapy and the physician has less flexibility in adjusting dosage regimens which is fixed by the dosage regimens. The characteristic of the ideal drug candidate for oral SR formulation includes; a drug which is not effectively absorbed in the lower intestine, the drug with a short biological half-life (<3 h), large dose drug, and drug with low therapeutic index.[147,148]