Side effects of phenoxymethylpenicillin

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Anon15041
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#1
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What are the on and off-target effects of phenoxymethylpenicillin? Any help would be greatly appreciated x
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xsha
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explosive diarrhoea
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Anon15041
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(Original post by xsha)
explosive diarrhoea
Anything more specific?
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a_w_
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Feeling really naueaseas and availability to eat well or at all. Just drink a lot of sweet drinks like squash. Personal experience...
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Anon15041
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(Original post by a_w_)
Feeling really naueaseas and availability to eat well or at all. Just drink a lot of sweet drinks like squash. Personal experience...
Thank you so much! But I need to state whether the side effect is on target or off target.
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macpatgh-Sheldon
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[On and off-target are not proper terms in pharmacology]

I assume that by "on-target" you mean the intended pharmacodynamic effects, and by "off-target" side effects.

The intended effect of the penicillins is inhibition of synthesis of peptidoglycan [they actually inhibit the last stage of this process = completion of the cross-link that confers strength to the molecule and involves binding of a glycine residue to a D-alanine residue], which is the major component of bacterial cell walls. The failure to make a cell wall leads to the blighters bursting = dying!! - this helps treat the infection.

Diarrhoea as a side effect [could be called "off-target", I suppose] is due to destruction by the same mechanism as above of the bacterial flora of the intestines, which play a part normally in digestion of cellulose [we humans, unlike cows [and other ruminants], cannot synthesize cellulase [mainly cos very few people eat grass lol]].

A serious side effect is, of course, an allergic reaction [although unusual] in the form of anaphylactic shock, which can be fatal, so every prescription should be preceded by a question to the patient about any previous such reaction.

Penicillin V [phenoxymethylpenicillin], being acid-resistant is given orally [unlike penicillin G [benzylpenicillin, which needs to be given IM.

Although both these penicillins are effective against gram-positive bacteria, their use now is limited due to the development of bacterial resistance, and the appearance on the market of numerous 2nd and 3rd generation penicillins e.g. ampicillin, methicillin. cloxacillin.
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Anon15041
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(Original post by macpatgh-Sheldon)
[On and off-target are not proper terms in pharmacology]

I assume that by "on-target" you mean the intended pharmacodynamic effects, and by "off-target" side effects.

The intended effect of the penicillins is inhibition of synthesis of peptidoglycan [they actually inhibit the last stage of this process = completion of the cross-link that confers strength to the molecule and involves binding of a glycine residue to a D-alanine residue], which is the major component of bacterial cell walls. The failure to make a cell wall leads to the blighters bursting = dying!! - this helps treat the infection.

Diarrhoea as a side effect [could be called "off-target", I suppose] is due to destruction by the same mechanism as above of the bacterial flora of the intestines, which play a part normally in digestion of cellulose [we humans, unlike cows [and other ruminants], cannot synthesize cellulase [mainly cos very few people eat grass lol]].

A serious side effect is, of course, an allergic reaction [although unusual] in the form of anaphylactic shock, which can be fatal, so every prescription should be preceded by a question to the patient about any previous such reaction.

Penicillin V [phenoxymethylpenicillin], being acid-resistant is given orally [unlike penicillin G [benzylpenicillin, which needs to be given IM.

Although both these penicillins are effective against gram-positive bacteria, their use now is limited due to the development of bacterial resistance, and the appearance on the market of numerous 2nd and 3rd generation penicillins e.g. ampicillin, methicillin. cloxacillin.
Thank you sooo much. That’s really helpful
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nexttime
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You got a great answer above, but this is really something that would have been extremely easy to Google.
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Anon15041
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#9
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(Original post by nexttime)
You got a great answer above, but this is really something that would have been extremely easy to Google.
It’s really not. I searched it and plenty of side effects came up but nothing specified which were on/off-target.
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nexttime
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#10
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(Original post by Anon15041)
It’s really not. I searched it and plenty of side effects came up but nothing specified which were on/off-target.
That's because its not a thing, as explained to you in the answer above.
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