Q. MOA of lactulose in hep. encephalopathy? - USMLE Forums
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Old 08-15-2015
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Default Q. MOA of lactulose in hep. encephalopathy?

In FA GI pharma, it's mentioned that In hepatic encephalopathy, lactulose is useful because when lactulose is given it is acted upon by gut flora converting it into lactic acid and lactic acid in turn promotes nitrogen excretion as ammonium.

But, In wikipedia and other resources it is mentioned that lactulose converts ammoina ( absorbable and toxic form) to ammonium ( not absorbable through gut and is non-toxic) and increase transit of bowel content through gut.

I am confused. which of the mechanism of action is correct ? If both is correct, Can anybody pls help me to fill up what I am missing to combine them together and give a meaningful sense to both MOA mentioned above.Thanks.
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Old 08-15-2015
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Well,
After taking a Lactulose, gut bacteria convert it to lactic acid ( bacterial action on lactulose->acidification of hepatic contents), lactic acid traps ammonia, which is absorbable and damaging and converts it to non-absorbable ammonium, which is excreted by feces->fecal nitrogen excretion.
I get it like this
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Old 08-15-2015
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Thanks mannaMD for the explanation. After reading more, I simplified it like this but I would like members in this forum to verify my understanding and correct if find anything wrong.

Lactulose is acted upon by gut flora converting it into lactic acid and acetic acid and thus formed lactic/acetic acid in turn will convert ammonia to ammonium which is not absorbed through gut and is excreted via faces.Is it so?
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Old 08-15-2015
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Lactulose is converted to Lactic Acid....its an acid...makes the gut ph low

Normally NH3(Ammonia) is secreted into the gut but its a gas can enter the gut and return back to blood vessel being highly lipid soluble...but

here since the ph is low ie acidic so the NH3 captures an H+(hydrogen ion) to become NH4+ and gets stuck in the bowel lumen...being charged can't re-enter blood vessels...

So if we use lactulose NH3 will be get into the gut but will not be able to return to the blood vessel thus NH3+ will be excreted...and save the patient from hepatic encephalopathy!

So yup you are right
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Thanks cleverfox.You put the scattered beads of information and strung them together in a good harmony.
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