Sierra Acai Company
Sierra Acai Company
Open 7 Days a Week
MonaVie Independent Distributor
Distributor Training
Shop Online
Enroll Now
Buy Wholesale and maintain an Active status for 2 months and we will refund your $39 Distributor Fee
Friends
Buy Wholesale and maintain an Active status for 2 months and we will refund your $39 Distributor Fee
07-SEPTEMBER-2008 03:17:44 - half-life For other uses, see Half-life disambiguation. The biological half-life of a substance is the time it takes for a substance drug, radioactive nuclide, or other to lose half of its pharmacologic, physiologic, or radiologic activity, as per the MeSH definition. Biological half-life is an important pharmacokinetic parameter and is usually denoted by the abbreviation t1/2.1 While a radioactive isotope decays perfectly according to first order kinetics where the rate constant is fixed, the elimination of a substance from a living organism follows more complex kinetics. See the article rate equation. This article may require cleanup to meet 's quality standards. Please improve this article if you can. July 2007 Contents 1 Examples of biological half-lives 1.1 Water 1.2 Alcohol 1.3 Prescription medications 1.4 Metals 2 Rate equations 2.1 Zero-order elimination 2.2 First-order elimination 3 See also 4 References 5 External links Examples of biological half-lives Water The biological half-life of water in a human is about 7 to 10 days. It can be altered by behavior. Drinking large amounts of alcohol will reduce the biological half-life of water in the bodycitation needed. This has been used to decontaminate humans who are internally contaminated with tritiated water tritium. Drinking the same amount of water would have a similar effect, but many would find it difficult to drink a large volume of water. 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. Alcohol The removal of ethanol alcohol through oxidation by alcohol dehydrogenase in the liver from the human body is limited. Hence the removal of a large concentration of alcohol from blood may follow zero-order kinetics. Also the rate-limiting steps for one substance may be in common with other substances. For instance, the blood alcohol concentration can be used to modify the biochemistry of methanol and ethylene glycol. 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. Note that methanol is very toxic and causes blindness and death. A person who has ingested ethylene glycol can be treated in the same way. Prescription medications Substance Half-life Notes Amiodarone 25 days Cisplatin 20 to 30 minutes Chlorambucil 1.53 hours Digoxin 24 to 36 hours Fluoxetine 1 to 6 days The active metabolite of fluoxetine is lipophilic and migrates slowly from the brain to the blood. The metabolite has a biological half-life of 4 to 16 days. Methadone 15 to 60 hours, in rare cases up to 190 hours.2 Oxaliplatin 14 minutes3 Salbutamol 7 hours Metals The biological half-life of caesium in humans is between one and four months. This can be shortened by feeding the person prussian blue. The prussian blue in the digestive system acts as a solid ion exchanger which absorbs the caesium while releasing potassium ions. For 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. Attempts to remove a substance from the whole organism may have the effect of increasing the burden present in one part of the organism. 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. Polonium in the body has a biological half-life of about 30 to 50 days. Caesium in the body has a biological half-life of about one to four months. Lead in bone has a biological half-life of about ten years. Cadmium in bone has a biological half-life of about 30 years. Plutonium in bone has a biological half-life of about 100 years. Plutonium in the liver has a biological half-life of about 40 years. Rate equations Zero-order elimination There are circumstances where the half-life varies with the concentration of the drug. 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. Thus the half-life, under these circumstances, is proportional to the initial concentration of the drug A0 and inversely proportional to the zero-order rate constant k0 where: t_1/2 = \frac0.5 A_0k_0 \, First-order elimination This process is usually a logarithmic process - that is, a constant proportion of the agent is eliminated per unit time Birkett, 2002. Thus the fall in plasma concentration after the administration of a single dose is described by the following equation: C_t = C_0 e^-kt \, Ct is concentration after time t C0 is the initial concentration t=0 k is the elimination rate constant The relationship between the elimination rate constant and half-life is given by the following equation: k = \frac\ln 2t_1/2 \, Half-life is determined by clearance CL and volume of distribution VD and the relationship is described by the following equation: t_1/2 = \frac\ln 2.V_DCL \, 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. So, for example, digoxin has a half-life or t½ of 24-36 hours; this means that a change in the dose will take the best part of a week to take full effect. For this reason, drugs with a long half-life e.g. amiodarone, elimination t½ of about 90 days are usually started with a loading dose to achieve their desired clinical effect more quickly. See also Browsing MeSH: Entrez MeSH Browser GoPubMed above MeSHine Reference.MD SHARing Point List of qualifiers - 2008 Half-life, pertaining to the general mathematical concept in physics or pharmacology. Kinetics References Birkett DJ 2002. Pharmacokinetics Made Easy Revised ion. Sydney: McGraw-Hill Australia. ISBN 0-07-471072-9. ^ International Union of Pure and Applied Chemistry. biological half life. Compendium of Chemical Terminology Internet ion. ^ Manfredonia, John March 2005. Prescribing Methadone for Pain Management in End-of-Life Care. JAOA-The Journal of the American Osteopathic Association. Retrieved on 2007-01-29. ^ Ehrsson, Hans et al Winter 2002. Pharmacokinetics of oxaliplatin in humans. Medical Oncology. Retrieved on 2007-03-28. External links Small Molecule Drug Half-life prediction software Retrieved from http://en..org/wiki/Biological_half-life Categories: Radiochemistry | Nuclear chemistry | PharmacokineticsHidden categories: Cleanup from July 2007 | All pages needing cleanup | All articles with statements | Articles with statements since January 2007 Views Article Discussion this page History Personal tools Log in / create account Navigation Main page Contents Featured content Current events Random article Search Go Search Interaction Community portal Recent changes Contact Donate to Help Toolbox What links here Related changes Upload file Special pages Printable version Permanent link Cite this page Languages العربية Bosanski Deutsch Español Galego Italiano Português Suomi Tiếng Việt Türkçe This page was last modified on 21 August 2008, at 04:11
39 Reasons to Drink Acai Juice Every Day
What is MonaVie - Watch the 8-minute video
Discovering MonaVie Video
The Power of You Video
Effects of MonaVie Active on Antioxidant Capacity in Humans
Log into your Wholesale MonaVie Account
So many of us do not eat a balanced diet, get enough sleep, have too much stress, or are impacted with toxins and pollutants. Drinking 2 ounces of MonaVie twice a day will help your body detoxify as well as build your immune system. Its the smartest thing you can do for yourself, so start today. Buying MonaVie through our company guarantees you support 7 days a week and, if you would like to share MonaVie with your family and friends we will guide you from start to finish.
1. Click on Enroll Now (30 - 55% off retail price)
2. Pay $39 for your Wholesale ID number.
3. NO minimum order required.
4. MonaVie is delivered to your door in 3 to 5 days.