Acetazolamide and chronic renal failure

[bolam]

I was taught today that acetazolamide is used in the treatment of chronic renal failure in order to correct alkalosis ( due to its activity as a carbonic anhydrase inhibitor). However I like to read about all the drugs we are lectured on in the BNF and here is states that this drug is contra indicated in renal impairment with the specific instruction to avoid due to acidosis.
I am a bit confused....
I did further research to find that acetazolamide is used when vominting symptoms occur in renal impairment.does this mean the drug is only indicated when there is vomiting as a result of renal impairment in order to counterract the alkalosis from this. Otherwise its contraindicated.

No biggie.. im just curious

[Nik]

I'm a bit confused here. Doesn't renal failure lead to acidosis, not alkalosis, as H+ ions are retained ? Kidney usually excretes H+ and CRF means it accumulates and binds bicarbonate, hence the acidosis and why acetazolamide is contra-indicated ? Never heard of acetazolamide being used for nausea/vomiting in CRF. Would have thought anti-emetics like cyclizine would be given.

[bolam]

Renal failure does lead to acidosis but I think its the vomiting that causes the alkalosis and thus this is why acetazolamde is used but I just find it strange to use a contra idicated drug when like you say there is other options. I guess maybe the lecture is a bit outdated?!?
It has no mention of acetazolamide use in vomiting in the BNF.

[crit care]

i don't claim to be an expert and i don't fully understand the pharmacology...i have seen acetazolamide being used to treat acidosis and promote alkalosis in patients who are acidotic based on blood gas results. i did ask the dr at the time and he explained it but can't remember it now

it has something to do with bicarbonate and it pushes the equilibrium one way over the other, i can picture some sort of equation relating hydrogen ions, CO2 and HCO3-

[Nik]

The closest the BNF comes to recommending acetazolamide for sickness is prophylaxis for mountain sickness, an unlicensed indication. Perhaps the lec is outdated as I thought a D2 antagonist or cyclizine would be more effective and less of a hassle to use. However it's been a year since I've covered renal failure in depth at uni so I may be missing something.