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Definitions And Explanation Of Commonly Used Terms

Guest buyer2015

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Guest buyer2015

People have been posting some technical terms in various threads and some people may not have any idea or fully understand what they mean and may want to so they get better understand what people are talking about. The definitions all refer to medications and how they work. I'm sorry it is so long but it has to be to explain it properly. If you already know what these mean or don't care, there is no need to read it all if you don't want to.


The first is;


Half life - Sometimes referred as the elimination half life.


The half life of a drug is referring to the length of time it take your body to metabolize (ie; break down) the drug in your body. Example; if you take 20mg of drug XXXXX and the half life is stated to be 4 hours, then in four hours you have an amount of active ingredient in you body that is half the original dose, in this example half of 20mg or 10mg. It is not to be confused as being the total time for the effects to last. In another 4 hours the amount is cut in half again, so after 8 hours you now have half of the 10mg after the first 4 hours or 5mg. This continues until all of the drug has been metabolized(the 5mg goes to 2.5mg after 12 hours then to 1.25mg and so on). Normally the effect you feel from the drug is not exactly what the amount is so after one half life, in this example 10mg, the effect is normally not the same as it would be if you were to take a starting dose of 10mg because for most people, it is hard to tell what the effect is since any amount taken that is less then the starting amount is difficult to feel. This is why the length of the drugs effects is usually close to one half life, in this case most would feel the drugs effects for close to 4 hours even though there is still some of the drugs active ingredient in your system.


When it comes to drugs that have a long half life, an good example being mea-the-don, that has a long half life ranging from 7-65 hours, the drug can build up in your system and eventually cause problems like having to much. Some people will start with an initial amount and somewhere around its first half life they feel that the effects have worn off, so they take another dose and after a while, they can get way to much in their system.


Bioavailability - sometimes spelled bio-availability


The bioavailability of a drug is given as a percentage amount, like 50%. It refers to how much of the initial dose of a particular drug is actually absorbed into your system and ends up in you bloodstream. This figure can vary depending on the method it is taken (its ROA). All drugs have a 100% bioavaiability when put directly into the bloodstream. With other ROA's this figure can change because the drug has to pass through some type of membrane(s) like your veins outer wall, your skin, etc and these act like a filter and do not let all of the molecules through. In addition to the type and total amount of membranes it has to pass through, the total surface area of these membranes also affects its bioavaiability and that is why there are usually different bioavailability's for each different ROA's. The size and shape of the actual molecules is what makes these figures vary for different drugs going through the same membrane(s).


Kind of like the children's toy where you have the ball with different shaped holes in it and you have to put the pieces that match the holes to get them through. It varies a little as the different pieces, molecules in this case, can be smaller or bigger then the holes in the ball, so a triangle shaped piece may go through a square hole, if the triangle piece happens to be small enough that it will still go through a different shaped hole. Depending on the drugs molecules and the method it is taken the numbers usually go down but if they are small enough they may fit through any opening. This is why the newer drugs that are being developed are referred to as small molecule medicines so they have a higher bioavailability with the easier and safer methods of ingesting them, such as orally. This is also why a lot of older drugs had to be put directly into the bloodstream to be absorbed properly and work and now most drugs are almost as effective orally as the are when put directly in.


A good example of one of the first drugs that was synthesized and altered to change its molecule so it has a higher bioavaiability, is the drug developed by Bayer pharmaceuticals in the late 1800's call the Hero-in town. Basically they took an existing drug, Mo-fein, which has a very poor bioavaiability by most ROA's and changed its molecule so that it would pass through the various membranes easier. This made the drug stronger and more effective. In some cases like this one, this also helps the drug get through what's called the blood brain barrier which is basically just another barrier that the molecule has to get through in order to get into your brain, where in this example, most of the drugs receptors are.


Some drugs, especially the opy's, have much different bioavailabilities depending on the ROA and this must be considered because when comparing an opy's strength with another opy one drug may vary much differently by ROA then another. A good example, and one of the most extreme, is when you compare the drug okseay-more-fone's (aka Opaino) with okseay-codon (aka oksea-continue) When put directly into the bloodstream okseay-more-fone's is 100% but when taken orally, it is only 10%. When comparie to something like okseay-codon (aka oksea-continue) that has a relatively high bioavailability, as high as 87% when taken orally, 80mg of oksea-codon equals to 40mg oksea-more-fone's If they are taken orally. If put directly into the bloodstream, it would only take 8mg of oksea-more-phone's to equal 80mg of oksea-continue.


The links for the opy analgesic convertors kindsty(user name) has posted in the section "All about pain and pain medicines" section, are an excellent way to figure out the differences for most drugs and ROA's.


I hope I explained this is in a way that everyone can understand. If you have any questions or need further explanation, please post it here in case someone else needs more clarification as well.

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