Myths in Clinical Pharmacology
1. Why this Myth Exists
The only measure of clearance that the ordinary clinician runs into is that for creatinine, and even that is only very rarely. On those rare occasions, the principles are simple; a patient with a high serum creatinine concentration almost certainly has a reduced creatinine clearance. That means a reduced glomerular filtration rate and, thus, renal failure.[1,2] Meanwhile, the creatinine clearance is usually not actually measured; after all, getting an accurate 24-hour urine collection in an intensive care unit is hard enough, let alone from ambulant outpatients. So, even the Cockroft-Gault formula (which converts creatinine clearance into glomerular filtration rate), is also now largely unused except by specialist nephrology services.[3,4]
Hence the myth -if higher serum creatinine concentration means lower creatinine clearance, then why should drugs be any different? The answer is because drugs are not usually being administered as a continuous intravenous...
The genesis of this article lies with well qualified physicians and pharmacists at a well respected university in California who not only hold this myth to be true, but also repeatedly have disputed the author’s suggestion of the alternative. Other less combative and former holders of this myth have been amongst those studying for the Diploma of Pharmaceutical Medicine of the Royal Colleges of Physicians of the United Kingdom. They are all acknowledged.
No sources of funding were used to assist in the preparation of this editorial. The author has no conflicts of interest that are directly relevant to the content of this editorial.
- 2.Taskapan H, Theodoros P, Tam P, et al. Glomerular filtration rate estimated from serum creatinine predicts total (urine and peritoneal) creatinine clearance in patients on peritoneal dialysis. Int Urol Nephrol. Epub 2010 Apr 4Google Scholar