Modeling/Biotech: Half-life of drugs in the body

Title:

Model of the Half-Life of Drugs in the Body

Objective:

When developing a new drug, scientists have no way of knowing the exact effects
of that drug on human physiology. Part of this is dependent on how long the drug 
remains active in the system. The purpose of this project is to develop a 
physiological based pharmacokinetic and pharmacodynamic (PBPK/PD) computer 
model of the human circulatory system and excretory systems, as well as of all
other tissues affected by a drug, that could estimate the duration of that drug, 
both in significant and trace amounts.

Justification:

When developing new drugs, researchers must go through many stages of testing, 
which can take over 12 years to get approved by the FDA for the public. This is 
made up of 3.5 years of laboratory research, 6 years of human testing, and 2.5 
years for the FDA to review and approve it, after which it requires more testing 
before actually being sold. A model of different chemical and drug half-lives in the 
human body could help shorten this process by helping to show early on what the 
life-span of the drug will be in the human body, which will allow the process to be 
sped up slightly, especially in the human testing phase. It could also help identify 
ineffective or dangerous drugs sooner (drugs that pass to quickly through the body 
or that remain to long), which would save millions of dollars on the unnecessary 
experimentation that would follow, and would make the overall cost of successful 
drugs cheaper for those who need them. A stronger understanding of the 
medications doctors are issuing would also increase the effectiveness of the 
treatment.

Description:

The PBPK/PD model will take into account many different properties of a drug, input 
by the user, to determine that drug’s course in a person. In order to limit the 
variables, the model will probably be limited to a certain type of drug, such as 
cardiovascular medications. These also have the advantage of having a large 
amount of research already done on them, to give a solid basis for calculating the 
half-life of unknown drugs. Important properties that can effect the drugs course 
include the size, moieties, likelihood of forming bonds to different substances it 
may come in contact with, dosage, shape, and rate at which it can be broken 
down or excreted intact. The model will also take into account different body 
types, sizes, ages, and genders. It will be able to determine how long the drug 
remains in an amount significant enough to affect the body, as well as how long 
trace amounts remain.

Limitations:

The main limitation is a source of data on which to base the calculations off of. 
As previously stated, it is very difficult to know what a drug will do prior to any 
sort of testing. By using the model for one type of drug, I hope to be able to 
find a mathematical basis for the model. This will require a lot of research and 
data analysis, which will be even more difficult because a lot of the research was 
done by private companies, and may not be available for public use. There is 
also the factor of the variability of patient response to the drug. I hope to make 
the model capable of being able to calculate the drug’s half-life for at least the 
big differences in different humans, such as gender, size, and relative age.