Urinary excretion rate

FIGURE 5. PCP urinary excretion rate versus the midpoint of the urine collection time in three dogs... 

Thus, the overall elimination rate constant (ke[) here is the sum of the urinary excretion rate constant (ke) and the metabolism rate constant (km) ... 

This optimization method, which represents the mathematical techniques, is an extension of the classic method and was the first, to our knowledge, to be applied to a pharmaceutical formulation and processing problem. Fonner et al. [15] chose to apply this method to a tablet formulation and to consider two independent variables. The active ingredient, phenylpropanolamine HC1, was kept at a constant level, and the levels of disintegrant (corn starch) and lubricant (stearic acid) were selected as the independent variables, X and Xj. The dependent variables include tablet hardness, friability, volume, in vitro release rate, and urinary excretion rate in human subjects. 

Validation of the model. The Perbellini model was validated using a data set for venous blood /7-hexane values in volunteers exposed for 4 hours (Veulemans et al. 1982). The range in the study was 334-368 g/L during exposure to 204 ppm the model predicted a value within this range. After 4 hours exposure to 102 ppm, the predicted value for venous blood -hexane concentration was about 10% below that actually observed in humans. The authors also compared their own data from previous studies on the correlation between venous blood -hexane concentrations and workplace concentrations. From the correlation curve, exposure at 102 ppm would predict a venous blood concentration of 176 g/L the model predicted 182 g/L. The urinary excretion rate of 2,5-hexanedione predicted by the model was also compared to a data set from 13 workers followed for 24 hours from the beginning of a workday. 

In another experiment, the ranking of urinary excretion rates of salicylic acid and four of its derivatives paralleled, both in rabbits and in man, the extent to which the drug was bound to plasma proteins. The most extensively bound salicylate had the longest plasma half-life and the least extensively bound, the shortest (Kl). 

Absorption/Disthbutton - After administration of a single dose of 100 mg, maximum blood levels are reached in approximately 4 hours, based on the mean time of the peak urinary excretion rate the peak excretion rate is approximately 5 mg/h the mean half-life of the excretion rate is approximately 15 hours. 

A commonly used indicator for fluoride exposure is its concentration in urine [85,99]. The urinary excretion rate of fluoride correlates better with its concentration in plasma than in urine [85]. 

J. Ekstrand, M. Ehmebo, The relationship between plasma fluoride, urinary excretion rate and urine fluoride concentration in man, J. Occup. Med. 25 (1983) 745-748. 

Statistical Moments Parameters that describe the characteristics of the time courses of plasma concentration (area, mean residence time, and variance of mean residence time) and of urinary excretion rate. 

T in plasma from repeated doses. They found that a maximum concentration was reached after 3 days when the rate of 2,4,5-T clearance from plasma equaled the amount ingested. The analogy can be applied to the urinary excretion amounts, also, because plasma clearance rate was exactly the same as the urinary excretion rate. Therefore, it would appear that the aerial workers (Table IV, Figure 3) had essentially reached the maximum 2,4-D excretion plateau. 

Schaub et al. demonstrated that Mrp2/MRP2 is expressed in the proximal tubules in the kidney (241,242). In vivo study and clinical study supports that Mrp2/MRP2 is involved in the tubular secretion of organic anions. The urinary excretion rates of calcein and fluo-3 were three to four times lower in perfused kidneys from TR rats compared with normal rats, and the renal excretion of lucifer yellow was delayed in TR rats (243). Hulot et al. identified a heterozygous mutation, which results in a loss of function of MRP2, in the patient who showed delay of renal MTX elimination (244). 

Urinary excretion rates have been measured in humans after oral exposure to several chromium compounds (Finley et al. 1996b). A group of four male and two female volunteers ingested capsules containing chromium(ni) picolinate at a dose of 200 pg/day for 7 days, to ensure that chromium deficiency was not a confounding factor. They then ingested 0.005 mg/kg/day chromium(VI) as potassium chromate (3 days), and 1.0 mg/kg/day chromium(III) as chromic oxide (3 days), with 3 days... 

Normally dietary NA is hydrolyzed by pancreatic ribonucleases and absorbed in the small intestine. Guanine and adenine are metabolized further to uric acid before urinary excretion (2). Increased consumption of NA increased the uric acid levels above the urinary excretion rate, resulting in an increased plasma uric acid level. Uric acid has a pKa near 5.4. In the acidic urine, as much as half of the excreted compound may be in the form of the undissociated acid, which has a low solubility... 

Renal clearance (Cl) of any compound (X) can be determined by comparing the urinary excretion rate of compound X to the plasma concentration of compound X. 

Fig. 7.2 Urinary excretion rates following administration of the anhydrate (A) and trihydrate ( ) forms of ampicillin. (From Brittain and Grant 1999, with permission.)...

Urinary excretion rate Rg day 10-200 Human health Oldfield (1999)... 

The urinary excretion of 8-oxodG in pigs following i/v injection follows simple kinetics with a half-life of a about 2.5 hours, a clearance of about 4 mL min kg BW and a volume of distribution close to 1 L kg BW [17], and moreover the urinary excretion rate corresponded to the infusion rate. After liver transplantation we observed an increased urinary excretion of 8-oxodG and in a caval clamp experiment the excretion was temporarily reduced. These experiments indicate that steady state between formation and urinary excretion is obtained rapidly. 

The reported values of urinary excretion of 8-oxodG in the literature are in agreement. The reported 8-oxodG urinary excretion rates measured with HPLC-ECD or GC-MS [18] vary from about 100 to 600 pmol kg BW 24 h, excluding the measurements with immunologically based estimations that vary between 1600-4800 pmol kg BW-1 24 h most presumably for the reasons about lack of specificity given above. 

It can further be argued that comparing two persons with different oxidative stress to DNA, i.e. different urinary excretion rates, the one with the higher stress will statistically have a higher chance for a mutation in DNA. Increased levels can not necessarily be interpreted in the same way, unless it can be established whether it originates from increased stress or decreased repair. 

The three major parameters examined in urinary excretion bioavailability studies are the cumulative amount of drug excreted unmetabolized in the urine ( Xu)-, the maximum urinary excretion rate (ERmax) and the time of maximum excretion rate (Tmax)- In simple pharmacokinetic models, the rate of appearance of drug in the urine is proportional to the concentration of drug in the systemic circulation. Thus, the values for Tmax and ERmax for urine studies are analogous to the Tmax and Cmax values derived from blood level studies. The value of r ax decreases as the absorption rate of the drug increases, and increases as the... 

Fig. 10 Relationship between urinary excretion rate of scopolamine and its pharmacological effects 10% of a parental dose of scopolamine is excreted in the urine unchanged.

When furosemide was incorporated in a GRDF by Klausner et al., Hhe device was delayed in the stomach up to 5 hr as detected by X-ray, and its drug delivery and absorption profile were shown to be slow and extended as described in the urinary excretion rate... 

Fig. 4 Kinetics of furosemide urinary excretion rate on duration of furosemide absorption following the administration of a GRDF and immediate release tablets containing 60 mg of furosemide to healthy volunteers (n = 14). (From Refl l)...

Large doses of caffeine cause diuresis. Daily consumption of caffeine citrate increased the mean urinary excretion rate of tubular cells and erythrocytes in volunteers (25). The nephrotoxicity of analgesic antipyretic drug combinations may result from a combined effect, in which aspirin, phenacetin, and caffeine all play a role (SEDA-4, 5). In 10 asymptomatic women and 20 women with confirmed detrusor instability, caffeine caused a significant increase in detrusor pressure on bladder filling in the latter, but no difference in volume at first contraction, height of contraction, or bladder capacity (26). 

Some individuals with hypercalciuria (an elevated urinary concentration of calcium) are prune In the formation of Ca -enniaining. stnnes within the urinary tract. Becau.se Inng-temi use of thiazide and thiazide-like diuretics de-crea.ses the urinary excretion rate of Ca". they may help prevent Ca" -containing stone fnrmation. "... 

Cone EJ, Welch P, Paul BD, Mitchell JM. Forensic drug testing for opiates III. Urinary excretion rates of morphine and codeine following codeine administration. J Anal Toxicol 1991 15 161-6. 

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