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Author Topic: Aspirin and amphetamine overdose  (Read 16205 times)

drkev

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Aspirin and amphetamine overdose
« on: 13/05/2004 17:55:16 »
Hi all. I am doing some coursework but I am stuck. I have to answer two questions about aspirin and amphetamine overdose.

I know that to treat an aspirin overdose one can increase the acidity of the blood to increase the rate of excretion and I would like to include an example of a drug that does this.

Also to treat an amphetamine overdose, one can decrease the acidity of the blood to increase the rate of excretion.

I have done the work myself but would just like to give an example of drugs that can do this in case I can get an extra mark.

Any help from the physicians on here would be much appreciated. Thanks

Live long and Love life

Kevin Fisher


 

drkev

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Re: Aspirin and amphetamine overdose
« Reply #1 on: 13/05/2004 17:57:14 »
I've typed that the wrong way round haven't I shouldnt type so quickly.

To increase salicylic acid excretion i should increase alkilinity and to increase amphetamine excretion i need to increase acidity.

But what drugs are commonly given?

Live long and Love life

Kevin Fisher
 

Offline bezoar

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Re: Aspirin and amphetamine overdose
« Reply #2 on: 14/05/2004 00:20:34 »
I can give you what I remember from the ER.  We always, of course, got an IV started.  With both drugs, you would do a gastic lavage or induce vomiting with ipecac, then follow with activated charcoal to try to absorb what is left.  The Tylenol overdoses drank and solution we usually used as a respiratory treatment in a venti-mask called Mucomist.  Smelled like a fart.  I never knew how anyone could drink it.  

Severe acidosis could, I suppose, be handled with sodium bicarb, although I've never seen it used for the aspiring overdoses.  I know we used to give vitamin C to the PCP ingesters (ASCORBIC ACID).  I don't know that you want to screw with the blood pH all that much, since there's such a narrow range fir life compatibility.  The other thing about Tylenol is that it's very hepatotoxic, which is why we had them drink the Mucomist -- it binds to the Tylenol to help with excretion.  Most of the drugs were either supportive, or to help absorb or excrete whatever could be gotten rid of.  I don't recall ever doing anything drastic to balance the pH of the blood, although we always checked it.  Maybe I just didn't get any that were that severe.  Had a salicylate level in the 500's with one patient, and she was lethargic, but coherent.  What tipped me off were those long deep breaths as her body kept trying to blow off CO2 to compensate for the acidosis caused by the aspirin.  Remember that the body will compensate for metabolic acidosis or alkalosis via the respiratory system.
 

Offline Donnah

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Re: Aspirin and amphetamine overdose
« Reply #3 on: 14/05/2004 00:53:47 »
Ah, so that's why the old folk remedy says pop your head outside and take a few deep breaths to reduce acidity.
 

drkev

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Re: Aspirin and amphetamine overdose
« Reply #4 on: 14/05/2004 12:27:07 »
thanks for your reply but i already handed the coursework in. I did manage to find the answers in my copy of Rang, Dale and Ritter but I was up all night.

One could reduce plasma pH through the administration of a carbonic anhydrase inhibitor such as acetazolamide but this would increase the risk of toxicity to the central nervous system so it is safer to alkalinise the urine with IV Sodium Bicarbonate.

For the amphetamine overdose I suggested ammonium chloride to decrease urinary pH. Although this is rarely used clinically it is sometimes used.

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Kevin Fisher
 

Offline chris

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Re: Aspirin and amphetamine overdose
« Reply #5 on: 16/05/2004 06:19:28 »
Hi Kev

sorry, I didn;t get to reply in time.

Just to clarify the above, we virtually never make people sick following overdoses these days. There is no evidence that this helps.

Instead we administer a large dose of activated charcoal (to bind up any unabsorbed drugs still in the GI tract), and then treat the patient symptomatically.

In the context of amphetamines patients usually present with agitation, restlessness, tremor, hyperreflexia, rapid respiration, confusion, hallucinations, and panic.

They can also develop irregular heart beat (arrhythmias), hypertension, or hypotension and circulatory collapse.

Gastrointestinal symptoms include nausea, vomiting, diarrhoea, and abdominal cramps.

In severe overdoses the patient may present with seizures (convulsions) and coma. These cases can be fatal.

You can stop the fits and reduce agitation with diazepam. Hypertension should be gently controlled with short-acting agents so you can titrate dose to blood pressure (and BP will fall with the sedative effects of diazepam anyway).

You then rely on normal excretion mechanisms to remove the amphetamine load. The reason for using ammonium chloride is that it can acidify the blood. At blood pH (7.4) the amphetamine molecule is unionised and, being lipophilic, it slips back across the cell membranes of the kidney tubules with relative ease when it is filtered. However, if the blood is acidified, the kidney acidifies the urine to remove the excess acid. In acidic urine the amphetamine molecule ionises (becomes charged) which greatly reduces its lipophilicity and hence the efficiency with which it can move back across the cell membranes of the kidney tubule cells into the blood stream. Confined to the urine in this way, the amphetamine is removed from the body more efficiently. This method is seldom used, however.

In the context of aspirin overdose exactly the same mechanism applies, but in reverse. At alkaline pH aspirin is ionised (because it is an acid). Therefore you can promote aspirin loss in urine by making the blood, and hence urine, even more alkaline with the administration of IV bicarbonate.

Chris

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Re: Aspirin and amphetamine overdose
« Reply #5 on: 16/05/2004 06:19:28 »

 

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