Creatinine clearance endogenous

In a study of 102 cases of occupational lead poisoning, 17 cases of clinically verified chronic nephropathy were found (Lilis et al. 1968). Endogenous creatinine clearance was <80 pg/dL. The mean PbB level for the entire study population was 80 pg/dL (range, 42-141 pg/dL). Nephropathy was more common among those exposed to lead for more than 10 years than among those exposed for less than 10 years. 

A study of 55 adolescents who had been treated for lead intoxication in early childhood (11-17 years earlier) revealed no evidence of chronic nephropathy, as evidenced by endogenous creatinine clearance, BUN, serum uric acid, and routine urinalysis (Chisolm et al. 1976). PbB levels during the acute poisoning episode ranged from 100 to 650 pg/dL all patients received immediate chelation therapy. At the time of the study, their PbB levels had decreased to less than 40 pg/dL. 

P743 was tested on a validated multiple-insult rat model [35] involving transient renal ischemia, dehydration, uninephrectomy and selective injection of a high dose (about 1.8 gl kg ) into the single remaining kidney and was found to have only minimal effects on GFR (evaluated by the endogenous creatinine clearance) and induced moderate enzymuria (NAG release into the final urine) or proteinuria. The effects observed were lower than those of the HOCA diatri-zoate [25]. 

An instructive example is the physiological variable serum creatinine. Creatinine is an endogenous metabolite formed from, and thus reflecting, muscle mass. Total body muscle mass is sufficiently constant to render measurement of serum creatinine useful for assessing actual renal function. The serum value of creatinine (R) is namely dependent on the continuous (zero-order) input of creatinine into the blood (A in) and its renal elimination rate, which is a first-order rate process (A out x ) In case of an extensive muscle breakdown, kin will temporarily increase. It may also be permanently low, for example in old age when muscle mass is reduced. Likewise, creatinine clearance may decrease for various reasons, described by a decrease in A out- An increase in creatinine clearance may occur as well, for example following recovery from renal disease. According to pharmacodynamic indirect response models. 

Endogenous creatinine clearance may also be used to estimate GFR. A single timed urine collection and matched plasma sample are used. Clearance is calculated as noted above. 

The limitations of the Jaffe method for creatinine determination are discussed under Assessment of Renal Injury by Serum Chemistry . Exogenous creatinine clearance compensates for the insensitivity of the method as well as the interference by endogenous chromagens by artificially increasing the plasma creatinine concentration (Finco 1997). 

Carvounis CP, Nisar S, Guro-Razuman S (2002) Significance of the fractional excretion of urea in the differential diagnosis of acute renal failure. Kidney Int 62 2223-2229 Dunn SR, Qi Z, Bottinger EP et al. (2004) Utility of endogenous creatinine clearance as a measure of renal function in mice. Kidney Int 65 1959-1967... 

Dunn SR, Qi Z, Bottinger EP et al. (2004) Utility of endogenous creatinine clearance as a measure of renal function in mice. Kidney Int 65 1959-1967... 

Measurements such as creatinine clearance have been used successfully to adjust dosing regimens for drugs eliminated primarily by the kidneys. Measures of hepatic function have been sought using endogenous... 

The renal clearance of the drug is proportional to endogenous creatinine clearance, irrespective of the mechanisms (i.e., filtration, reabsorption, or secretion), and the creatinine clearance is used as an indicator of the severity of the disease. Furthermore, it is possible to predict the half-life of a drug in a patient with renal disease based on the creatinine clearance and on a knowledge of the pharmacokinetics of the drug in normal subjects, as illustrated with cefazolin in Fig. 3. 

Creatinine, an endogenous end product of muscle metabolism, is often measured in plasma and urine to determine creatinine clearance. Since, creatinine is freely filtered at the glomerulus and is not reabsorbed or secreted by the proximal tubule of most species, creatinine clearance provides a good measure of the GFR. Another endogenous compound, urea, is also cleared mainly by renal filtration and excretion. Increases in the blood or serum concentration of urea are indicative of decreased GFR. However, increases in BUN concentration occur only after substantial renal damage has been established. Thus, BUN concentration is not a sensitive indicator of nephrotoxicity and changes usually occur later than changes in other parameters (e.g., enzymuria). 

The most widely used endogenous marker of GFR is creatinine, expressed either as its plasma concentration or its renal clearance. The use of creatinine as a marker of GFR was developed in 1926 by Rehberg, who used exogenously administered creatinine. This led to the work of Popper and Mandel, who in 1937 developed the use of endogenous creatinine clearance. 

Because creatinine is endogenously produced and released into body fluids at a constant rate, its clearance has been measured as an indicator of GFR. A protocol for the conduct of the creatinine clearance test may be found in the third edition of this textbook. 

The final component of the dialysis prescription that may affect drug clearance by dialysis is whether or not the patient has anthorized the unit to reuse his or her dialyzer. Currently, more than 75% of all dialysis units in the United States use this procedure to reduce the cost of chronic hemodialysis. The effect of dialysis filter reuse on the clearance of endogenous molecules such as urea, creatinine, and P2-microglobulin has been evaluated for many dialyzers. A decrease in urea and creatinine clearances and an increase in /S2-mictoglobulin clearance was observed with some, but not all, dialyzers. Only one center has evaluated the effect of reuse on drug clearance (cefazolin, ceftazidime, tobramycin, and vancomycin) following the first and tenth use of cellulose acetate, cellulose triacetate, and polysulfone... 

In summary, monitoring changes in the creatinine clearance or directly measuring the GFR using markers that are not acted upon by the tubule are the best tools to detect early drug-induced renal toxicity in patients with a normal baseline creatinine concentration. Serial monitoring of the serum creatinine concentration is usually adequate in those chronic failure patients whose creatinine is already increased. The role of other endogenous compounds such as cystatin C as a way to monitor renal function is not yet known. 

Although direct methods provide a more accurate measurement of GFR for a particular patient, these methods are time-consuming and require analytical methods that are not always readily available. As a result, GFR is routinely estimated based on the endogenous marker, creatinine clearance. Creatinine clearance is most commonly measured indirectly using any number of equations that have been developed based on a patient s measured serum creatinine (5C). These equations are based on patient characteristics such as age, gender, body weight, and height... 

Creatinine clearance (Cld) is renal clearance (Cl,) applied to endogenous creatinine. It is used to monitor renal function and is a valuable parameter for calculating dosage regimens in elderly patients or those suffering from renal dysfunction. Normal creatinine clearance (Clc) values are ... 

Glomemlar filtration rate (GFR) was estimated through endogenous creatinine clearance and the rate of urate filtration from GFR and semm urate. The pyrazinamide suppres-sible part of the urate excretion was the intial excretion (UV-ur) minus the minimum excretion during PZA suppression (UV-ur, min). The tubular reabsorption of filtered urate (TR-ur) was calculated from GFR and the minimum urate clearance during PZA... 

Renal handling of uric acid was examined in 30 patients with primary gout (mean age, 44 years), and in 10 normal controls (mean age, 33 years). A normal GFR, as assessed by means of endogenous creatinine clearance, was a pre-requisite for being included in the... 

Determination of daily and fasting urinary uric acid and electrolytes (endogenous creatinine clearance) controls, P, n = 20 oxalic stones, i.e. hypercalciuria, HC, n = 30 uric acid stones, HS, n = 16 primary hyperparathyroidism, HPT, n = 15 ... 

Endogenous creatinine clearance Plasma and urine over 12 h or24h Dog Overestimation of GFR due to tubular secretion and non-creatinine chromogens... 

Burry, H. C. and Dieppe, . (1976) Apparent reduction of endogenous creatinine clearance by salicylate treatment. Brit. med. J., 2, 16. 

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