BACKGROUND: The French National Authority for health recommends that the adjustment of the dosage of drugs in patients with renal insufficiency be carried out on the basis of an estimate of renal function using the Cockcroft-Gault formula, while the estimation of the glomerular filtration rate using the Modification of Diet in Renal Disease or CKD-EPI formula is recommended for the diagnosis and monitoring of renal insufficiency. The argument put forward is that the recommendations for dosage adjustment of the summaries of product characteristics would have been established on the basis of the use of this formula. Service ICAR aimed at verifying the evidence supporting this argument.
METHODS: In all, 2447 summaries of product characteristics were analyzed to identify the renal function criterion specified for dose adjustment recommendations. When no formulas were found in the summary of product characteristics, the firms were contacted to obtain information on renal function estimation methods used in developmental studies. Their responses were analyzed.
RESULTS: Of the 2447 summaries of product characteristics studied, 438 (17.9%) propose a dosage adjustment in case of renal insufficiency. No formula is mentioned in the summarie of product characteristics for 90.0% of them. The Cockcroft-Gault and Modification of Diet in Renal Disease/CKD-EPI formulas are found in 8.7% and 0.7% respectively of these 438 summaries of product characteristics. After contacting pharmaceutical companies and analysis of the data available in the studies on which the summaries of product characteristics were based, the information cannot be found for 63.0% of the summaries of product characteristics, in spite they mention the need to adjust the dosage in case of renal insufficiency.
CONCLUSIONS: The majority of summaries of product characteristics do not mention the Cockcroft-Gault formula and in the majority of cases it is not possible to identify the formula or technique used in the studies on which is based the reference to dosage adjustment in the summarie of product characteristics. In addition, there are discrepancies between the wording of the summaries of product characteristics and the data from development studies. The use of Cockcroft-Gault for dosage adjustment is to be questioned, especially since the Isotope-dilution mass spectrometry, or IDMS, standardization of creatinine dosage makes obsolete studies based on Cockcroft-Gault formula and a non-standardized dosage, and thus the use of Cockcroft-Gault not transposable to current clinical practice.

Ten percent of the world\'s population is affected by chronic kidney disease that can lead to kidney failure. In France, nearly three million people are concerned, half of whom are undiagnosed, 85,000 people are on dialysis or waiting for a kidney transplant. Each year, 11,000 new diagnoses of severe renal failure are made, one third of which had not been treated before. Kidney failure is constantly increasing due to the aging of the population and the resurgence of chronic diseases, including obesity and cardiovascular diseases such as high blood pressure and diabetes, two conditions that impair renal function. The pharmacist, a local actor, is well placed to help patients adhere to their treatment and manage it to the best of their quality of life. It is up to the pharmacist to check the dosages according to the degree of renal involvement, ideally noted on the prescription or, failing that, by asking the patient the results of his recent biological examinations. The consultation of the pharmaceutical file and, ultimately, the shared medical file, will make it possible, in a concerted management of the patient\'s care pathway, to also detect possible drug interactions. By dispensing the prescribed drugs, the pharmacist can also warn against those known to be known for their nephrotoxicity, especially nonsteroidal anti-inflammatory drugs. In the case of over-the-counter products, the pharmacist may discourage a person at risk from taking certain drugs containing nonsteroidal anti-inflammatory drugs, including aspirin and ibuprofen. Because of their potential renal toxicity, the pharmacist is competent to alert, especially on certain food supplements, herbal products, and is legitimate to participate in screening campaigns.

While the CKD-EPI (for Chronic Kidney Disease Epidemiology) equation is now implemented worldwide, utilization of the Cockcroft formula is still advocated by some physicians for drug dosage adjustment. Justifications for this recommendation are that the Cockcroft formula was preferentially used to determine dose adjustments according to renal function during the development of many drugs, better predicts drugs-related adverse events and decreases the risk of drug overexposure in the elderly. In this opinion paper, we discuss the weaknesses of the rationale supporting the Cockcroft formula and endorse the French HAS (Haute Autorité de santé) recommendation regarding the preferential use of the CKD-EPI equation. When glomerular filtration rate (GFR) is estimated in order to adjust drug dosage, the CKD-EPI value should be re-expressed for the individual body surface area (BSA). Given the difficulty to accurately estimate GFR in the elderly and in individuals with extra-normal BSA, we recommend to prescribe in priority monitorable drugs in those populations or to determine their \"true\" GFR using a direct measurement method.

Chronic kidney disease is a progressive disease which has become a real public health issue. In patients with renal disease, drugs pharmacokinetics may be altered. The handling of drugs requires a special attention in these patients. Indeed, there is a risk of accumulation and drug overdose if dosage is not adjusted to the stage of renal insufficiency. Thus, to achieve a dosage adjustment knowing how to evaluate renal function is absolutely necessary. Different formulae are available including the Cockcroft and Gault formula aMDRD and CKD-EPI. In patients with cardiac issues, it appears that the CKD-EPI formula is that of choice in terms of clinical risk stratification. However, some summaries of product characteristics (SmPC) of drugs used in cardiology, such as Dabigatran(®), mention the need to use the Cockcroft-Gault, less accurate than aMDRD and CKD-EPI, in order to adjust the dose in patients with impaired renal function. Standardization of recommendations is necessary to limit disparities in dosage and drug exposure according to the formula. SmPCs however, are not the only source of information to obtain data on the use of drugs in the renal insufficient population. Some other information sources exist, reliable, updated and easily accessible.