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post #1 of 11 (permalink) Old 07-07-2009, 11:32 AM Thread Starter
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theory behind medicine dosages

Okay, I know car forum isn't exactly the best place to ask, but I am curious about something.

What is the theory behind the dosage amount and frequency for different medicines? I can't seem to find anything other then dosage calculators when I search for different things.

I am guessing it was in animal trials they found the LD/50 dosage lets call it X. They then figure the effective dose (IE enough to cause the effect that they are looking for) calling it Y. They then discover through trails what a normal healthy person's half life for the medication is calling it Z.

I am guessing so long as 2*y is no where near X then y is a safe effective dosage amount and Z is an effective dosage interval (corresposponding to readministration of the medicine at its half life, rounded to the nearest convenient hour).

That way the overall exposure never exceeds twice the initial dose, but the levels in the body generally don't dip below an effective amount at any point while continuing administration of the medicine. I am guess this would of course vary depending on the medicine quite a bit as some might have an effective dose at a certain level, but slightly below that it isn't effect and slightly above that runs in to LD/50 levels. I am speaking more of OTC things like Acetomenaphine, benadryl, etc.
-Matt
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post #2 of 11 (permalink) Old 07-07-2009, 11:50 AM
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Re: theory behind medicine dosages

99% of otc is safe unless you take the whole bottle....i built up such a tolerance to sudaphed (not the pussy stuff nowdays) i had to take 8 to even get anything out of them....Acetomenaphine will just mess your stomach up....benedryl makes you nauseous....etc....all minor overdose issues....

animal trials, not sooo much...people trials....people get paid money you know to try new drugs....


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post #3 of 11 (permalink) Old 07-07-2009, 01:08 PM Thread Starter
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Re: theory behind medicine dosages

I realize the LD/50 of just about anything OTC is way, way about 'recommended' levels, as I mentioned I was mostly curious about how they derived recommended dosage levels and more specifically frequency.
-Matt
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post #4 of 11 (permalink) Old 07-07-2009, 01:15 PM
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Re: theory behind medicine dosages

Its going to based upon what the average individual can withstand before either being poisoned or have huge adverse effects. Then it depends on how quickly it breaks down in the body. So as you said its going to vary greatly between different medications.

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post #5 of 11 (permalink) Old 07-07-2009, 01:32 PM
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Re: theory behind medicine dosages

[quote author=daafisch link=topic=149790.msg3214654#msg3214654 date=1246986913]
Its going to based upon what the average individual can withstand before either being poisoned or have huge adverse effects. Then it depends on how quickly it breaks down in the body. So as you said its going to vary greatly between different medications.
[/quote]

Yeah, I imagine it has to do with liver/kidney effects (which most medicines have some), minimum dosage required to be effective and the length of time before your system filters it out.
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post #6 of 11 (permalink) Old 07-07-2009, 01:56 PM
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Re: theory behind medicine dosages

[quote author=gar187er link=topic=149790.msg3214468#msg3214468 date=1246981842]animal trials, not sooo much...people trials....people get paid money you know to try new drugs....
[/quote]
yes exactly, you can make some money by doing those test, but i would never try it.
all drugs pretty much have to be tested on humans before humans can start commercially use it.

why the question??? researching n how to properly overdose some1 :P

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post #7 of 11 (permalink) Old 07-07-2009, 04:14 PM
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Re: theory behind medicine dosages

[quote author=eurotuner link=topic=149790.msg3214719#msg3214719 date=1246989415]
[quote author=gar187er link=topic=149790.msg3214468#msg3214468 date=1246981842]animal trials, not sooo much...people trials....people get paid money you know to try new drugs....
[/quote]
yes exactly, you can make some money by doing those test, but i would never try it.
all drugs pretty much have to be tested on humans before humans can start commercially use it.

why the question??? researching n how to properly overdose some1 :P
[/quote]

each drug has to go on a minimum of 8-9 years study on animal, human, and lab tests before it can be sold in the U.S


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post #8 of 11 (permalink) Old 07-07-2009, 05:16 PM
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Re: theory behind medicine dosages

Animal trials aren't generally aimed at killing the animals so much as just finding the effective dose. They are tested at different mpk levels for effectiveness, and the half life is determined, which determines the frequency of the dosage. The level of dosing that gives the desired effect on the target gives the recomended dosing.
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post #9 of 11 (permalink) Old 07-07-2009, 11:35 PM
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Re: theory behind medicine dosages

If you are looking for specific answers as to how they arrive at certain dose levels do some research into Pharmacokinetics and Pharmacodynamics. Basically they(i.e. Really smart guys in lab coats) figure out what the minimum effective dose( the least amount needed to have a beneficial effect) and the maximum effective(the maximum amount that can be given before it starts to harm the body) doses are. In between the two values is called the therapeutic index range. You basically want to keep the drug levels in between these two values. The next thing that plays into the mix is the ability of the body to eliminate said drug from your body, more specifically Half-life's. Most drugs are eliminated via the liver and kidneys over a certain period of time. High/low blood pressure greatly effect kidney function which is why you see it so much as warnings in drug commercials. The lab coat guys use this information and some other important need to know info to determine how many times per day you need to take said drug to keep the drug levels in your system in the therapeutic range. IE you need to take X amount of drug every 12 hours in order for it to have a therapeutic effect on your body. Some drugs require a loading dose in order to reach theraputic levels then drop said dose due to long half life and elimination issues. But like I said look into Pharmacokinetics, it's pretty interesting stuff. I had to to take Pharmacology in school. It's a bitch of a class but interesting none the less.

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post #10 of 11 (permalink) Old 07-08-2009, 09:16 AM Thread Starter
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Re: theory behind medicine dosages

[quote author=allmannbro link=topic=149790.msg3215720#msg3215720 date=1247024119]
If you are looking for specific answers as to how they arrive at certain dose levels do some research into Pharmacokinetics and Pharmacodynamics. Basically they(i.e. Really smart guys in lab coats) figure out what the minimum effective dose( the least amount needed to have a beneficial effect) and the maximum effective(the maximum amount that can be given before it starts to harm the body) doses are. In between the two values is called the therapeutic index range. You basically want to keep the drug levels in between these two values. The next thing that plays into the mix is the ability of the body to eliminate said drug from your body, more specifically Half-life's. Most drugs are eliminated via the liver and kidneys over a certain period of time. High/low blood pressure greatly effect kidney function which is why you see it so much as warnings in drug commercials. The lab coat guys use this information and some other important need to know info to determine how many times per day you need to take said drug to keep the drug levels in your system in the therapeutic range. IE you need to take X amount of drug every 12 hours in order for it to have a therapeutic effect on your body. Some drugs require a loading dose in order to reach theraputic levels then drop said dose due to long half life and elimination issues. But like I said look into Pharmacokinetics, it's pretty interesting stuff. I had to to take Pharmacology in school. It's a bitch of a class but interesting none the less.
[/quote]

Thanks for the info!
-Matt
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