Avaliação do ritmo de filtração glomerular / Assessment of glomerular filtration rate

A medida do ritmo de filtração glomerular (RFG) é a prova laboratorial mais utilizada na avaliação da função renal. Para tanto, usam-se marcadores indiretos, como as determinações de creatinina e cistatina C no sangue, ou procede-se à determinação do RFG propriamente dito, com indicadores como inulina; contrastes iodados, marcados ou não; e outras substâncias. O exame mais solicitado para avaliação do RFG no laboratório de patologia clínica é a dosagem da creatinina sérica. Em algumas condições, entretanto, o resultado encontrado da creatinina sérica deve ser corrigido (através da utilização de fórmulas que levam em consideração características próprias do indivíduo) para ser devidamente interpretado. De fato, a inulina ainda é vista como marcador ideal de filtração glomerular, mas seu uso não se destina à prática clínica, de modo que ainda hoje persiste a busca por testes adequados para uso rotineiro.

Glomerular filtration rate (GFR) determination is the most frequently used laboratorial test to evaluate renal function. Indirect markers as blood determination of creatinine and cystatin C are used with this purpose, as well as the direct determination of GFR, with indicators like inulin; iodated contrasts, radioactive or not; and others. Serum creatinine is the test that is most commonly performed in order to evaluate GFR in the clinical pathology laboratory. However, in some conditions, aiming at the adequate interpretation of the test, the result of serum creatinine must be corrected (by using formulas that include individual characteristics of the subjects). In fact, inulin is still seen as the ideal marker of glomerular filtration, but its use is not directed to clinical practice; then the search for appropriate tests for routine use continues.

Avaliação da filtração glomerular através da medida da cistatina C sérica: [revisão] / Glomerular filtration evaluation employing serum cystatin C measurement: [review]

A avaliação acurada da função renal através da medida da filtração glomerular (FG) é fundamental na rotina clínica, pois é parte decisiva do diagnóstico e terapêutica. A dosagem sérica de creatinina é o método mais usado, embora apresente limitações, como interferências na dosagem e baixa sensibilidade na detecção de graus menos avançados de perda de função renal. Outros métodos, como depuração de inulina, iohexol, 125I-iotalamato e 51Cr-EDTA, também são descritos com o mesmo propósito, mas são complexos e caros. Desta forma, investigadores ainda buscam um marcador ideal para analisar a função renal. Neste contexto, se encaixam os estudos com a cistatina C, uma substância endógena, que vem sendo relatada como um indicador confiável e de fácil execução. A cistatina C é um membro da família dos inibidores da cisteína protease e está presente em uma variedade de células nucleadas,sendo produzida de forma constante. A sua medida, comparada à da creatinina, sofre menos interferências e apresenta maior acurácia na detecção dereduções incipientes da função renal. O objetivo desta revisão é descrever a medida da cistatina C como uma alternativa confiável para avaliar a FG,analisando valores de referência e usos clínicos.

An accurate evaluation of renal function with glomerular filtration rate (GFR) measurement is essential in clinical practice, as it defines diagnostic andtherapeutic decisions. Serum creatinine is the most utilized method. However, it has several limitations, such as the influence of drugs and endogenoussubstances on its measurement, and a low sensitivity for detecting less advanced degrees of renal dysfunction. Other well-known methods, such as theclearances of insulin, iohexol, 125I-iothalamate, and 51Cr-EDTA have also been employed with the same purpose; however, these methods can be complexand expensive. Therefore, investigators are still searching for simpler markers to analyze renal function. Cystatin C, an endogenous substance, has beendescribed as a reliable and easy-to-perform indicator of GFR. Cystatin C is a member of the family of cystein protease inhibitors and is constantly produced by nucleated cells. Its measurement, when compared to creatinine, suffers less interference and is more accurate for the detection of incipient decreases of renal function. The aim of this review is to analyze the details of cystatin C measurement, such as reference values and clinical application.

Disposition kinetics and urinary excretion of cefpirome after intravenous injection in buffalo calves

We investigated the disposition kinetics and urinary excretion of cefpirome in buffalo calves after a single intravenous administration of 10 mg/kg. Also, an appropriate dosage regimen was calculated. At 1 min after injection, the concentration of cefpirome in the plasma was 57.4 +/- 0.72 microgram/ml, which declined to 0.22 +/- 0.01 microgram/ml at 24 h. The cefpirome was rapidly distributed from the blood to the tissue compartment as shown by the high distribution coefficient values (8.67 +/- 0.46/h), and by the drug's rate of transfer constant from the central to the peripheral compartment, K12 (4.94 +/- 0.31/h). The elimination halflife and the volume of distribution were 2.14 +/- 0.02 h and 0.42 +/- 0.005 l/kg, respectively. Once the distribution equilibrium was reached between the tissues and plasma, the total body clearance (ClB) and the ratio of the drug present in the peripheral to the central compartment (T/P ratio) were 0.14 +/- 0.002 l/kg/h and 1.73 +/- 0.06, respectively. Based on the pharmacokinetic parameters we obtained, an appropriate intravenous cefpirome dosage regimen for treating cefpiromesensitive bacteria in buffalo calves would be 8.0 mg/kg repeated at 12 h intervals for 5 days, or until persistence of the bacterial infection occurred.

Comparative bioavailability of two brands of ciprofloxacin.

Twelve adult healthy volunteers participated on two occasions in a cross-over study with an interval of 30 days. The bioavailability of ciprofloxacin 500 mg administered as single oral dose was compared in preparation A (Indian, Torrent) and preparation B (Imported, Bayer). The drug was administered early morning on an empty stomach. Blood samples were collected at 1/2,1,2,4,6,8,12 and 24 hours. Plasma levels of ciprofloxacin were determined by HPLC. Time taken to achieve peak plasma concentration (Tmax) was 2 hours (A) and 1.67 +/- 0.49 hours (B). Maximum plasma concentration (Cmax) ranged from 1.8 to 5.1 ug/ml (mean 3.08 +/- 0.99 ug/ml) for 'A' and 2.08 to 5.5 mu g/ml (mean 3.58 +/- 1.37 mu g/me for 'B'. Area under plasma concentration time curve ranged from 30.91 to 118.27 ug/ml/hr (mean 59.97 +/- 26.68 ug/ml/hr) in 'A' and 36.52 to 108.05 (mean 62.80 +/- 22.33 ug/ml/hr) in 'B' which is more than reported in Western literature. Large bioavailability of ciprofloxacin in the present study suggests the need to be cautious while treating patients with renal problems and to use lower doses in Indian patients to achieve desirable results. However, there was no significant difference in the pharmacokinetic parameters between the two brands (Paired 't' test and Wilcoxon Sign Rank test). It is therefore, concluded that both the preparations are comparable in terms of bioavailability.

Comparative bioavailability of two brands of norfloxacin.

Twelve adult healthy volunteers participated on two occasions in a cross-over study with an interval of 30 days. The bioavailability of norfloxacin 400 mg administered as single oral dose was compared in an Indian preparation A (Torrent) and imported preparation B (Merck Sharp and Dohme (MSD), USA). Plasma was separated from the blood and stored at -20 degrees C for analysis by High Performance Liquid Chromatography. Time taken to achieve mean peak plasma concentration (Tmax) was 2.00 +/- 0.74 hours in case of Torrent (A) and 1.70 +/- 0.49 hours in case of Merck Sharp and Dohme, USA (B). The maximum plasma concentration (Cmax) ranged from 1.60 to 2.87 ug/ml in Torrent (A) and 1.18 to 2.28 ug/ml in case of MSD (B). Area under plasma concentration curve (AUCO-12hr) was 12.70 +/- 3.2 ug/ml/hour for 'A' and 14.80 +/- 2.80 ug/ml/hr for 'B'. Elimination half life (t1/2) for Torrent (A) was 9.25 +/- 5.10 hours and for MSD (B) it was 12.05 +/- 1.05 hours. There was no significant difference in the pharmacokinetic parameters between the two brands (Student's 't' test). Increased elimination half life and large bioavailability (AUC) with both the preparations in the present study suggest the need to be cautious while treating patients with renal problems and to use lower doses in Indian population to achieve desirable kinetics of norfloxacin.

Tritium metabolism in man.

Tritium metabolism in human beings was studied in volunteers who had exposure to tritiated water accidentally, by measuring the organically bound tritium with liquid scintillation counter, in sperms and plasma proteins. 2% of the initial urinary tritium specific activity was incorporated as bound tritium in sperms. In plasma proteins, on the 20th day of exposure, tritium bound in globulin was 3 times higher than that of albumin, tritium bound in globulin was 3 times higher than that of albumin.