A kick in the kidneys

Another quarter, another batch of NICE guidance arrives on our doorstep.  This month sees the release of the headline grabbing ADHD guidelines, but also NICE's take on the management of Chronic Kidney Disease.

Alas, one key area for clinical pharmacists remains ignored - what to do in routine practice about drug dosing when a patient has impaired renal clearance. 

For the uninitiated, renal function is important as the kidneys are one of the two main ways that the body excretes drugs and other waste products.  If renal function is impaired, we have to either reduce the dose of the drug to allow for the resulting accumulation or choose another drug that is eliminated by other routes.

Until recently the Cockroft and Gault creatinine clearance equation would be routinely used for estimating renal drug handling (The number of years of age under 140 divided by the serum creatinine, multiplied by the weight in kilos and a factor of 1.23 or 1.04 depending on whether the patient's a man or woman respectively).  Depending on what this approximation to the renal clearance of creatinine comes back at, we can make an informed choice about how much accumulation is likely for a particular drug. 

DoH guidance in 2003 brought in the MDRD eGFR equation - more complicated but capable of being worked out automatically by the computer in the biochemistry lab.  The eGFR's purpose is to screen the population for kidney disease, so they can be treated earlier and lead happier healthier lives - which is a very very good thing.  Unfortuately for us pharmacists it's also frequently used by doctors for the purposes of adjusting drugs - a use for which it is at best unvalidated.  No-one knows if an eGFR can be used for anything other than screening and monitoring caucasians and afro-carribeans for kidney disease. 

Now NICE at one point seems to recognise this, but suggests using inulin or other "gold standard" markers for adjusting nephrotoxic drugs.  I don't know about other hospital pharmacists but I can't see us injecting radioactive tracer molecules into every patient that needs to receive chemotherapy, let alone other nephrotoxic drugs, or even drugs like nitrofurantoin which are either toxic or ineffective at mild renal impairment. 

Creatinine is measured in nearly every patient that crosses our threshold, and we have years of practice and research (admitedly this is of variable quality) to back up the use of Cockroft and Gault in patients.

Looking through the authors, I see many doctors and health economists but no pharmacists.  Why weren't the UK renal pharmacy group involved, so that we could get in black and white that this issue exists and needs resolving?

25-9-8