Pharmacokinetic estimation for therapeutic dosage regimens (PETDR) – a software program designed to determine intravenous drug dosage regimens for veterinary applications

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Abstract
Pharmacokinetic estimation for therapeutic dosage regimens (PETDR) is a software program used to design individualized intravenous dosage regimens, determine concentration-time profiles, predict serum concentrations at a specific time after intravenous dosing and predict the time after the last dose to achieve a specified concentration of drug. The reference pharmacokinetic parameters may be based on an individual animal''s pharmacokinetic disposition of drug or on FARAD (Food Animal Residue Avoidance Databank) mean population kinetic parameters. An individual animal''s kinetic parameters may be input for predetermined analysis or the program can calculate these values by input of raw serum concentration-time data. The program allows the user to specify certain parameters of the dosage regimen, then calculates the other parameters (given desired maximum and minimum serum concentrations, dose and interval are calculated; given desired maximum serum concentration and interval, dose is calculated, etc.). Given the kinetic parameters, the dose and dosing interval, the program calculates and plots the serum concentration-time profile of the drug for that animal. The time and the number of doses to reach steady state can be calculated as well as the determination of loading dose. The percentage of the time of a dosing interval at steady state that the serum concentration is above a specific minimum inhibitory concentration (MIC) allows evaluations of efficacy of an antimicrobial regimen. Similarly, the time to reach a specific concentration (e.g. residue tolerance) or the MIC of a drug can be calculated. Legal tissue tolerances can be accessed from FARAD to aid in predicting for what period of time illegal residues will remain in the animal. These calculations allow design of dosage regimens that maximize therapeutic efficacy and minimize toxicity to the patient as well as to decrease the incidence of drug residues in food animals.