Absorption number

Fig. 1. Approximate relationship between sound pressure level and distance as a function of room absorption. Numbers on the curves are metric sabins.

Absorption Number of Trays for Fixed Recovery of Key Component... 

Thus, the fraction of dose absorbed is exponentially related to the absorption number. Equation (10) shows that the absorption number (and therefore the membrane permeability) is a fundamental parameter while other parameters such as the partition coefficient and pKa are useful guides but not fundamental parameters. For highly soluble drugs with linear absorption kinetics, dose and dissolution have no effect on the fraction of dose absorbed. In the case of drugs that are absorbed by a carrier-mediated process, a mean permeability should be used [30],... 

Figure 5 Correlation of the fraction of dose absorbed with rat permeability. The rat permeability data were determined using the rat perfusion model. Considering the difference between the human permeability and the rat permeability, a scale factor was used to calculate the absorption number in Eq. (8). (Ref. 34 with kind permission from Plenum Publishing Corporation, New York.)...

Rewriting Eq. (43) in terms of the absorption number according to Eq. (8) results in... 

The human effective permeability Pcff in Eq. (59) is expressed in centimeters per hour. In terms of the dimensionless absorption number An, Eq. (58) can be written as... 

Further predictions of in vivo drug absorption could be obtained by using fundamental dimensionless groups such as Do (dose number), Dn (dissolution number), and An (absorption number). The three dimensionless numbers are combinations of physiochemical and physiological parameters and represent the most fundamental view of GIT drug absorption and are the foundation principles of the BCS [3], Do is calculated using Eq. 2.26 ... 

An = absorption number = Do = dose number = Dn = dissolution number =... 

Table4.1 Solutions to Eq. (15). Cs is drug solubility. C0 and Cf are the concentration at the beginning and at the end of the intestinal segment respectively. An - Absorption number, Do - dose number. See text for explanation.

BET SSA, Brunauer Emmett Teller specific surface area SSA, specific surface area DBPA, dibutyl phthalate absorption OAN, oil absorption number. 

The last two integrals of the previous equation are expressed in dimensionless variables, c = c/cq, z = z/L with normalized limits (0,1), while the symbol An is the absorption number of the drug ... 

This equation can be used in conjunction with (6.9) for the estimation of Fa. The microscopic approach points out clearly that the key parameters controlling drug absorption are three dimensionless numbers, namely, absorption number An, dissolution number Dn, and 9. The first two numbers are the determinants of membrane permeation and drug dissolution, respectively, while 9 reflects the ratio of the dose administered to the solubility of drug. 

At the end of the simulation time, the mass that was absorbed and the mass that has exited from the end of the tube can be computed. Further, the dimensionless absorption number An can be computed [153] from... 

The absorption number (An) is the ratio of permeability (Peff) and the intestinal radius (P) multiplied by the residence time (t,.es), which can be interpreted as the effective absorption rate constant (t. ) times the residence time ... 

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