Many antibiotics have adjusted dosages for those on hemodialysis to account for the reduced clearance of these drugs for those whose kidneys are not functioning.
However should these adjustments also apply to those on daily nocturnal dialysis? I am asking because I am assuming I get much better clearances compared to those on conventional thrice weekly dialysis. Should the dose be the same as those with normal kidney function? Or should the dose be somewhere in between?
Thanks!
Kamal
While quite a complex issue, in simple terms, we mostly actually leave the doses at the recommended levels that apply for that drug in standard dialysis-dependent CKD patients.
But, the truth probably lies somewhere in between. It can depend upon the antibiotic in question. This can (and does) apply to other drugs, too – and not just antibiotics … and can be influenced by whether the drug (or antibiotic) is, or is not, protein bound within the blood stream.
Some drugs (and antibiotics) can dialyse off – but, for most drugs, this is dialysance is insignificant. If a drug (or antibiotic) is protein-bound, this further diminishes or fully negates any loss on haemodialysis – regardless of the length of the therapy. This may change in future as more protein-leaky dialysers (eg the dialysers we now routinely use to treat light-chain depletion in multiple myeloma) are introduced. Some may mistakenly think it might be an issue with sorbent-based systems … but as sorbent dialysis applies only to dialysate regeneration and not to blood sorbency, this is not an issue.
While lengthening the session, increasing the frequency (or both) may have a small effect, for most drugs (or antibiotics) this increase will have little practical effect.
Drug metabolism may also affect the clearance of some drugs (and antibiotics) as some drugs are excreted whole and others are metabolized to drug fragments or sub-compounds before excretion.
While drug metabolism, drug excretion and the dialysability of a drug is studied as part of the information-base on a drug prior to marketing - at least this is so for most drugs – the difference in drug dialysability between the various modes of dialysis is far less well known and there are absolutely no (ie: zip) studies to compare standard HD with long, extended HD regimes.
So … do we know? No … we don’t. Do I presume little difference? Yes … I do. Is that good enough? No … perhaps not, but in practical terms, probably yes.
Thanks Dr. Agar for that response!