Biomedical subjects

V B Sarin

Publications and source records attributed to V B Sarin.

10 recordsLinked to original sources

PubMed1993

A three compartment open model with two time lags.

The present study deals with the identification of exchange parameters involved in a three-compartment open model with two time lags in which elimination occurs from the central compartment. Two different optimization methods have been used which involve the reduction of different unknowns to a single variable theta, with the help of Archimedes Spiral. Thus, the solution requires the global minimum of a functional of single variable theta. Results are compared with those obtained by the generalized least square method.

Absorption↗

PubMed1993

A four compartment open model with first-order absorption.

This paper is related to the identification of pharmacokinetic parameters of a four-compartment open model with first order absorption from plasma level data. The eigenvalues of the characteristic matrix of the given system are obtained by transforming them into a single variable and the solution involves the minimization of the sum of squares of deviation of the model-predicted values of the state variables from an experimentally obtained values. The distribution volume and the lag time are also identified. Finally, the unicity of the absorption rate constant is obtained by the minimum energy principle. The results obtained with present method are compared with those obtained by the generalized least squares method.

Absorption↗

PubMed1993

Flow of an elastico-viscous liquid in a curved pipe of slowly varying curvature.

Curvature forms an important feature of thoracic aorta and this paper deals with the flow of an idealized elastico-viscous liquid in a curved pipe of circular cross-section and slowly varying curvature, under a pressure gradient. The flow is assumed to be steady and at low Reynolds numbers. By using the series expansion method of Dean (Phil Mag 4 (1927) 208-223; Phil Mag 5 (1928) 673-693) in powers of a parameter L, which can be considered as the square of ratio of the centrifugal force induced by the circular motion of the fluid to the viscous force, it is shown that in a tube of increasing curvature, there will be delay in setting up of the secondary motion. The wall shear stress, an important parameter in physiological flows, is calculated. The flow of Newtonian fluid in a tube of circular cross section is discussed, as a particular case.

Aorta, Thoracic↗

PubMed1992

Stenotic effects in a tube of elliptic cross-section at low Reynolds numbers.

With an objective to understanding arteriosclerosis, the blood flow in a cylindrical tube with local constriction is analysed. The cross-section of the tube is an ellipse, the axes of which are in an arbitrary position with respect to the axis of the tube. Blood is taken to be a Newtonian and homogeneous fluid. The cross-sectional area varies slowly with the longitudinal distance and the area change is so adjusted to take account of stenosis. The transverse velocity field and the effects of inertia on the primary velocity and pressure distribution are calculated to a first order in the relevant small parameter and effects of asymmetry on the wall shear stress and impedance are presented.

Arteriosclerosis↗

PubMed1987

A four compartment model to study the kinetics of strontium metabolism in man.

Many drugs confer upon the body the characteristics of a four compartment model. This paper deals with the estimation of pharmacokinetic parameters of a four compartment model to study the distribution of strontium in the organism. The central compartment (where the introduction of the material takes place) is connected to two other compartments (which represent the organic fluids) and one of them is connected to the fourth compartment (which represents the fraction that can be exchanged in the bone). The elimination from the central compartment is through urine and the elimination from the third compartment is in the form of a non-exchangeable deposit. The method of solution involves an optimization method which provides the global minimum of delta, a single variable function. The model is tested for different sets of data and the results are compared with those obtained by the generalized least square method.

Computer Simulation↗

PubMed1987

A four compartment linear mammillary model.

Studies are made for a four compartment model in which the central compartment is connected reversibly to three other compartments and the elimination occurs from the central compartment only. Identification of different distribution rate constants is made, with concentrations of drug in the central compartment at different times of observation being known. The solution depends on an optimization method in which the different unknowns are reduced to single variable with the help of Archimedes spiral. Thus, the solution requires the global minimum of a functional of single variable. Results are compared with those obtained by the generalized least square method.

Kinetics↗

PubMed1986

A three-compartment open model with first order absorption.

Many drugs confer upon the body the characteristics of a three-compartment model. This paper deals with the estimation of pharmacokinetic parameters of a three-compartment open model, with first order absorption from plasma level data. The central compartment (e.g. plasma) is connected to two other peripheral compartments, and (elimination occurs from only the central compartment. The method of solution involves an optimization method which provides a global minimum of delta, the deviation of plasma concentration from the observed values. The distribution volume of the central compartment and the lag time are also identified. The uniqueness of the absorption rate constant is obtained by the minimum energy principle. The model is tested for different sets of data for the drug Guanfacine (Sandoz laboratories), and the results are compared to those obtained by the generalised least square method.

Absorption↗

PubMed1986

Pharmacokinetics of estulic [corrected] in humans.

Estulic [corrected] given orally without food after overnight fast produces a blood concentration curve with a pronounced second peak that does not appear when the drug is taken with food. A two-compartment open model involving two different time lags is used to study the pharmacokinetics of estulic [corrected] in humans after oral administration. The drug accumulates in a tissue or organ that is well perfused in the first pass transfer. The accumulation appears to occur by a competitive process. The second peak apparently is the result of a rapid release of drug and bioreversible drug compounds from the hepatic-biliary system with subsequent reabsorption. This release may occur spontaneously, but appears to be triggered by food intake. We use an optimization method to characterize the pharmacokinetic profiles of drug for this model. This technique which provides the global minimum of the deviation delta, from the given observations, leads to the optimization of a single variable function. The results are compared with those obtained from the generalized least squares method.

Absorption↗

PubMed1985

General treatment of linear mammillary models.

This paper deals with the mathematical analysis of time courses of absorption, distribution and elimination of drug in a body, which is of considerable value in developing dosage schedules to provide optimal therapeutic action and to reduce the unwanted side effects due to accumulation of drug in the body to a minimum. We consider a general n-compartment model, where elimination occurs from the central compartment which, in turn, is connected reversibly with all other compartments. This linear mammillary model can be used to study the kinetics of protein metabolism in organism. We use an optimization method to characterize the pharmacokinetic profiles of drug for a general n-compartment model. Results are compared to those obtained by making use of (a) SAAM program and (b) an asymptotic method.

Biometry↗

PubMed1985

Identification of pharmacokinetic parameters of two compartment open model with first order absorption.

This paper deals with the estimation of pharmacokinetic parameters of a two-compartment open model with first order absorption from plasma level data. The eigen-values of the characteristic matrix of the given system are obtained by transforming them into a single variable and the global minimum of the deviation (for plasma concentrations) from the observed values is obtained through the solution of linear relations involving the eigen-values. The distribution volume and the lag time are also identified. Finally, the uniqueness of the absorption rate constant is obtained by the minimum energy principle. The model is tested for different sets of data for the drug Guanfacine, an antihypertensive drug. The results are compared to those obtained by the SAMM program.

Absorption↗