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It's very good for every student like me. It means that a substance with a particular atomic weight, in course of time, gets reduced to half of the original atomic weight by emitting the radiations. It doesn't mean that only half of the substance decays. I went off the drug this morning and wondering how long before the drug clears my system. I've been on dynacirc cr for about six months and haven't had any problems until now with irregular heartbeats.
WHAT DOES HALF LIFE MEAN FULL
Why did we choose half life? why not full life. so the "other half" is not really a half at all. ISBN 0-07-471072-9.There is no "other half." Once the "first half" as you say, has decayed, the "other half" will divide in half, and then that quarter will divide in half, etc. Pharmacokinetics Made Easy (Revised Edition).
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In clinical practice, this means that it takes just over 4.7 times the half-life for a drug's serum concentration to reach steady state after regular dosing is started, stopped, or the dose changed. Thus the half-life, under these circumstances, is proportional to the initial concentration of the drug A 0 and inversely proportional to the zero-order rate constant k 0 where: For example, ethanol may be consumed in sufficient quantity to saturate the metabolic enzymes in the liver, and so is eliminated from the body at an approximately constant rate (zero-order elimination). There are circumstances where the half-life varies with the concentration of the drug.
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Cadmium in bone has a biological half-life of about 30 years.Lead in bone has a biological half-life of about ten years.Caesium in the body has a biological half-life of about one to four months.Polonium in the body has a biological half-life of about 30 to 50 days.For instance, if a person who is contaminated with lead is given EDTA in a chelation therapy, then while the rate at which lead is lost from the body will be increased, the lead within the body tends to relocate into the brain where it can do the most harm. Attempts to remove a substance from the whole organism may have the effect of increasing the burden present in one part of the organism. The prussian blue in the digestive system acts as a solid ion exchanger which absorbs the caesium while releasing potassium ions.įor some substances, it is important to think of the human or animal body as being made up of several parts, each with their own affinity for the substance, and each part with a different biological half-life. This can be shortened by feeding the person prussian blue. The biological half-life of caesium in humans is between one and four months. The metabolite has a biological half-life of 4 to 16 days.ġ5 to 60 hours, in rare cases up to 190 hours. The active metabolite of fluoxetine is lipophilic and migrates slowly from the brain to the blood. A person who has ingested ethylene glycol can be treated in the same way. Note that methanol is very toxic and causes blindness and death.
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In this way the oxidation of methanol to the toxic formaldehyde and formic acid in the human body can be prevented by giving an appropriate amount of ethanol to a person who has ingested methanol. For instance, the blood alcohol concentration can be used to modify the biochemistry of methanol and ethylene glycol. Also the rate-limiting steps for one substance may be in common with other substances. Hence the removal of a large concentration of alcohol from blood may follow zero-order kinetics. The removal of ethanol ( alcohol) through oxidation by alcohol dehydrogenase in the liver from the human body is limited. The basis of this decontamination method (used at Harwell) is to increase the rate at which the water in the body is replaced with new water. Drinking the same amount of water would have a similar effect, but many would find it difficult to drink a large volume of water. This has been used to decontaminate humans who are internally contaminated with tritiated water ( tritium). Drinking large amounts of alcohol will reduce the biological half-life of water in the body. The biological half-life of water in a human is about 7 to 10 days.