Consecutive Input Research Articles

A pharmacokinetic program for TI-59

A program for pharmacokinetic analysis and calculations by means of the inexpensive and generally available mini-calculator TI-59 in conjunction with the adaptable printer PC-100 A is presented and demonstrated. The program may be used in the analysis of plasma concentration curves originating from intravenous or paravascular administration of drugs with one- or two-compartment characteristics obeying first-order pharmacokinetics. In relation to peroral administration, one or two consecutive first order input steps may be used. The program incorporates routines for exponential regression analysis, extrapolation and determination of residuals, calculation of composite rate-constants and the corresponding zero-time concentration constants. Curves may be simulated by function tabulation thus allowing manual curve-fitting procedures and determination of a possible lag-time. Time-defined intravenous infusion substituting for bolus injection as well as multiple dose, steady state pharmacokinetics may also be treated by the program, which ends up with a routine procedure for calculation of the microscopic rate-constants, the various volumes of distribution, the area under the plasma concentration curve and total drug clearance. Lithium and dipyridamole plasma concentration data are used to demonstrate the practical application of the program.

A new implementation algorithm of second-order IIR digital filters

In the implementation of a second-order IIR digital filter, five multiplications and four additions are required for each output sample calculation. In this correspondence we present a new implementation algorithm which requires four multiplications and seven additions per output sample, and the output sequence can be produced at uniform rate without introducing any artificial delay in the filter. Since the number of operations (such as multiplication, addition, data transfer, etc.) between any two consecutive input samples are kept the same, the design of the control section is quite simple. For the circumstances where multiplication time dictates the filter speed, the new algorithm achieves 20 percent improvement on the filter speed.

Pharmacokinetics of dipyridamole.

Dipyridamole, though originally introduced as a coronary vasodilator, has lately been increasingly investigated in the treatment of thromboembolic diseases because of its inhibitory influence upon blood platelet function. The compound is eliminated from the organism by hepatic biotransformation to the monoglucuronide, which almost exclusively is subjected to biliary and faecal excretion with simultaneous partial enterohepatic circulation taking place. Only minute amounts are excreted through the kidneys. In experiments on four normal human volunteers it was found that the serum concentration curve after intravenous administration of dipyridamole rather closely fits the pharmacokinetics of an open two-compartment model with first order, linear disposition kinetics and elimination taking place from the central compartment. Experiments with oral ingestion of the compound could be described by the use of a corresponding pharmacokinetic model with two consecutive first order input steps, representing the dissolution and absorption processes. The disposition rate constants (beta) were within the range of 0.0051--0.0083 min.-1 corresponding to biological half-lives of 84--145 min. The absorption rate constant was about 0.07 min.-1, and the systemic availability of an oral dose of 100 mg dipyridamole in tablets varied from 37 to 66%.

An interaction model of a Poisson and a renewal process related to neuron firing.

This paper discusses a neuronal model based on a model of Coleman and Gastwirth (1969). It is assumed that the excitatory input forms a Poisson process while the inhibitory input forms a stationary renewal process. The proposed interaction scheme is as follows: an inhibitor deletes at most N consecutive excitatory inputs and a response only occurs after the cummalative storage of M excitatory inputs. The Laplace transform of the probability density function (p.d.f.) of the inter-response intervals is derived together with results of the numerical inversions.