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Pharmacology - Alprazolam half life?

Discussion in 'Benzodiazepines' started by bosch man, Jul 20, 2008.

  1. bosch man

    bosch man Silver Member

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    Alprazolam and half life

    Hi do i get this correctly:-

    if one was to take 1mg xanax (assume the halflife on me is 8 hrs)

    in 8hrs it would be 0.5mg

    in 16hrs it would be 0.25mg

    in 24hrs it would be 0.12mg

    and so on all the time halfing until completely gone from blood stream.

    If this is correct would i be right in thinking that 16 hours after taking a 1mg tab i would feel the equivilant to asthough i had just taken a 0.25tab?..and so on,if so it would explain why you should never mix with alcohol as even after 24hrs from 1mg you still have the effect of half a 0.25tab.

    Correct or totally wrong?

    bosch man added 3 Minutes and 29 Seconds later...

    ...and i assume 1 unit of alcohol clears the blood in approx 1 hour so if one drank 12 units it would take 12 hours to totally clear the system?So its half life is very short.
     
    Last edited: Jul 20, 2008
  2. Nargyle

    Nargyle Palladium Member

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    Re: Xanax and half life

    Half life doesn't necessarily mean the effects will still be present, plasma concentration is just as important, so even if there still is alprazolam in the system it won't necessarily be felt
     
  3. Solinari

    Solinari Titanium Member

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    Re: Xanax and half life

    Basically it is correct, plasma concentrations are how it's measured and after so many hours the plasma concentration's will be half what they were originally. The half life varies from person to person due to metabolic rate and other things probably, so up to 12 hours is the half life for alprazolam.

    If someone were to drink several hours after taking a single therapeutic dose of alprazolam the effects wouldn't be that prominent but it probably would have a marginal effect. The problem would come from repeated daily doses where there is a cumulative effect and one dose is skewed in to another.

    As for the alcohol thing, as far as i know the half life will not be effected by the amount, so if it were the same as something like alprazolam then 12 units would take the same time to clear as 1 unit, of course drinking time would have an effect on the overall time it would take to clear. I can't find a half life for alcohol and i am not so sure it's as simple as a set amount of time, but it will take 3 half life cycles for a drug to be considered eliminated.
     
    Last edited: Jul 20, 2008
  4. Nargyle

    Nargyle Palladium Member

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    Re: Xanax and half life

    Setting a half life for alcohool is not that easy because while most drugs have a half-life exponential metabolism. Alcohol has a steady-state linear metabolism. Why does this happen? Well you see the structure of alcohol(ethyl) is CH3CH2OH. Now the liver breaks it down into Acetaldehyde, which is much more poisonous to the body than alcohol itself. The liver proceeds to turn it into acetic acid so the enzymes that break down alcohol may be busy with the byproducts produced by the metabolism of alcohol.

    Basically since everything has to occur in a certain order before more alcohol can be broken down by the liver, the reaction is a zero order reaction.

    1. Binding of the coenzyme NAD+;
    2. Binding of the alcohol substrate by coordination to zinc;
    3. Deprotonation of the His-51;
    4. Deprotonation of nicotinamide ribose;
    5. Deprotonation of Ser-48;
    6. Deprotonation of the alcohol;
    7. Hydride transfer from the alkoxide ion to NAD+, leading to NADH and a zinc bound aldehyde or ketone;
    8. Release of the product aldehyde;
    All that has to happen before the liver can break down more alcohol because acetaldehyde is poisonous so the liver has to make sure it deals with that stuff first before breaking more alcohol down otherwise you're gonna get sick.
     
  5. Solinari

    Solinari Titanium Member

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    Re: Xanax and half life

    I had a quick look at Wikipedia's section on alcohol in the Biological Half-life page and ended up just skimming over after the first sentence, but that was a lot easier to read and understand, i had no idea that's what happened. Is that why alcoholics end up dying unless they stop drinking because the liver can't deal with the acetaldehyde?
     
  6. bosch man

    bosch man Silver Member

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    SWIM noted in an article that alprazolam is totally elimanated from the body in half a day, so around 12 hours but swim notes that the half life of this drug is around 12 hours:s Can anyone explain?!
     
  7. Boca Bitch

    Boca Bitch

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    Re: Half life

    The half life of alprazolam is 8hrs. This is the amount of time needed for the body to clear roughly half of the medication administered. Naturally, this is also the point in time where the medication starts to loose its therapeutic effect. There may be residual effects for hours after, but depending on the efficiency of one's hepatic/renal systems, it's usually unnoticeable. It can take as long as two-three days for benzodiazepines to be completely eliminated from the body.
     
  8. bosch man

    bosch man Silver Member

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    Re: Half life

    Are you saying that alprazolam if taken say 3 times daily can build up in one's system? I heard that you can actually get withdrawal between doses on this one. Also then in theory you could take say alcohol 8 hours later if you are feeling no effect from the drug without any problems or would the other "half" still be active to potentiate?
     
  9. EscapeDummy

    EscapeDummy Palladium Member

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    Re: Half life

    Yes, and yes. Benzo's can build up in the bloodstream, rapidly inducing tolerance, if they are taken several times a day due to their long half life. Roofies are a very potent benzo with a half-life of over 24 hours, if I remember correctly. Also, yes to your second question, just because you are no longer feeling the dose after a half-life, there is still alprazolam in your system, and any synergistic effects it has with alcohol can occur.

    Although, swim doesn't know of many people who have had problems taking alcohol many many hours after benzos, but since you said in theory, it could have an effect.