Clearance value range

Mean serum clearance values ranged from 9.4 to 28.9 mL/min/kg and were independent of dose. Mean terminal elimination half-life values ranged from 8 minutes to 4.3 hours and mean steady-state volume of distribution values ranged from 0.25 to 2.88 L/kg. IV dosing 3 times/week for 2 weeks resulted in no accumulation of interferon beta-la or beta-lb in the serum of patients. 

Considering that the actual clearance value ranges from the flight clearance to the channel depth, the pressure gradient over the screw flight can be approximated by ... 

For double-acting cylinders, % clearance is based on total clearance volume for both the head end and crank end of the cylinder X 100 divided by the total nel piston displacement. The head and crank end % clearance values will be different due to the presence of the piston rod in the crank end of the cylinder. The % clearance values are available from manufacturers for their cylinders. The values range from about 8% for large 36-in. cylinders to 40% for small 3-and 4-in. cylinders. Each cylinder style is different. 

Note that this requires or assumes that compressor cylinder clearance Vp be established. For studies, it may be assumed and the effects calculated. Values range from 5-35% clearance on actual cylinders. Special designs are used for smaller or larger values. 

The clearance of a drug is usually defined as the rate of elimination of a compound in the urine relative to its concentration in the blood. In practice, the clearance value of a drug is usually determined for the kidney, liver, blood or any other tissue, and the total systemic clearance calculated from the sum of the clearance values for the individual tissues. For most drugs clearance is constant over the therapeutic range, so that the rate of drug elimination is directly proportional to the blood concentration. Some drugs, for example phenytoin, exhibit saturable or dose-dependent elimination so that the clearance will not be directly related to the plasma concentration in all cases. 

In a first step the scaling of intrinsic clearances determined in rat hepatocytes was compared to in vivo clearance. When taking account of non-linearity, the estimated hepatic metabolic clearance values were in reasonable agreement with observed total clearances, which ranged from 7 to 35 mL/min/kg, and it was considered reasonable to estimate the expected clearances in human by a similar scaling of human hepatocyte data. The error around the mean predicted human clearance was based on the variability seen in different batches of human hepatocytes. 

A high CLR indicates the liver efficiently removes a drug from incoming blood, so F is low. A low f/. [ indicates high F. Hepatic clearance can range in value from 0 to 25 mL/min/kg. With this information, we can begin to put Equation 7.33 to its full use. 

It is then possible to extend this principal and calculate the proportion of individuals who fall within any given number of SDs of the mean. In standard tables, you can look up how many people should fall within 1,2,3, lVi or any other number of SDs of the mean. However, the only other case of special interest is that approximately 95 per cent of individuals fall within the range 2 SDs from the mean. Taking our clearance values, 2 SDs (31/h) below the mean would be 7.01/h and 2 above would be 13.01/h. Figure 3.6 shows the 95 per cent of individuals who fall in the wider range between 2... 

For example, for theophylline, the clearance value is 0.65mL/min/kg (2.34 L/h for a 60 kg man), the half-life in healthy non-smoking asthmatics is approximately 9h and the effective plasma concentration range is 5-15mg/L. Because the dose is an IV infusion, the systemic availability, C is 1. If the target plasma concentration at the steady state is lOmg/L, then the... 

The biotransformation of salicylic acid to salicyluric acid in Rhesus monkey has also been reported by Wan et al. (13). The dose of salicylic acid given intravenously to the monkey is equivalent to a 625-mg, dose for a 70-kg. man. The terminal half life for the animal studied was 50 min. (Fig. 8), which is shorter than the 3-4-hr. average half-life in man. The clearance value for salicylic acid estimated from the area under the curve was 10 ml/min or 1.8 ml/min/kg, in marked contrast to the data obtained for benzoic acid in rabbits where clearance was found to be between 44 and 115 ml/min or 12.6-28.8 ml/min/kg. In a single intravenous study in the monkey, benzoic acid was found to have a plasma clearance of 140 ml/min or 38.1 ml/min/kg. Plasma clearance of salicylic acid in man, at a dose level of about 500 mg administered intravenously, was found to be in the range of 0.57 ml/min/kg body weight according to the data of Riegelman et at. (14). The fraction of the dose excreted as salicyluric acid in 16 hr. was found to be 72%. 

Bioavailability is the other important conceptual pharmacokinetic parameter, in addition to clearance. The key concepts are summarised in Box 5.3. Bioavailability is defined as the proportion of an administered dose that reaches the systemic circulation . It has no units and is usually expressed as a percentage. Values range from 0 to 100%, and will be 100% or complete for an intravenously administered drug. After oral administration, only a proportion of the drug may reach the systemic circulation because of incomplete absorption or because absorbed drug may be metabolised in the gut wall or liver (first-pass metabolism). For... 

All chemistries were determined by the clinical laboratory at the University of Utah Medical Center. A detailed error analysis shows the range of errors for clearance value to be between 10% at the start of dialysis and 15% at the end of dialysis. Oncotic pressures were measured with a colloid osmometer (Model 186, Instrumentation Laboratories, Boston MA) to 0.2 mm Hg. 

Sotalol is excreted by glomerular filtration with approximately 75% of the drug being excreted within 72 hours (29). The reported elimination half-life ranges from 7-18 hours (29). As expected, reduced renal function (i.e., reduced creatinine clearance) results in reduced renal clearance values of sotalol. For example, renal clearance has been reported (34) to be reduced from a mean of 4.99 L/h (creatinine clearance > 80 ml/min) to a mean of 0.27 L/h (creatinine clearance < 10 ml/min). In fact, after chronic administration of sotalol, the serum half-life was reported to be 69 hours in an anuric patient (35). Although there is no difference in the enantiomeric clearance of sotalol (31), it has been suggested that the clearance of (-i-)-sotalol after administration of such may be reduced (36) as compared to its clearance when administered with an equal proportion of (-)-sotalol (i.e., when administered as racemate). 

Clearance determinations discussed so far all require measurement of concentrations in carefully timed urine and plasma samples. In addition, useful approximations to relative solute clearance values can be obtained by simplified procedures. The best known of these simply takes the plasma level of urea, or preferably creatinine, as a measure of the GFR. Indeed, if creatinine excretion (UV in g/day) is constant, the GFR (=UV/P) theoretically is inversely proportional to Pcr/ the creatinine concentration is plasma any increase in P r above a normal level of around 1 mg/dl should therefore reflect a corresponding fall in GFR. In practice the method is not very sensitive in the normal range of plasma creatinine levels (<1.4 mg/dl) a better correlation between measured creatinine clearance (Cc) and that predicted on the basis of Pcr is obtained at higher plasma levels, that is, lower Gcr values [6,21]. 

Typical values (range) of femoral head radius, radial clearance and effective radius for hip implants with various... 

A survey of the published literature indicates that the ratio of the maximum to mean energy dissipation rate in the vessel, Smax/ m can vary substantially but typically in the range 10 to 100 [85]. Recent measurements [100] of the turbulent flow properties with a range of impellers and vessel configurations indicate that the differences between the reported ratios of Smax/Cm re partly due to differences in the geometrical variables. For example, detailed factorial designs of experiments showed significant effects of impeller diameter to tank diameter ratio and off-bottom clearance to impeller diameter ratio on the value of emax/Cm-... 

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