The distribution of drug in the body comprises of many processes which are collectively called as pharmacokinetics. The process starts with administration where the drug comes in contact with the body. There are three different routes by which the drug enters the body and then is absorbed by the bloodstream.
Distribution of the drug is carried out by the bloodstream. The bloodstream takes the drug molecules to the tissue sites where it is required or will be most effective. The bloodstream also takes the drug molecules to different other sites in the body where the may need to metabolize, stored or may be eliminated from the body. When the drug molecules arrive at the intended destination of the drug, the drug molecules move towards the required tissues by passing through the cellular barriers (Knights, 2002). These barriers include all the boundary walls of the organs and the tissues which drug may need to cross in order to reach the intended place like kidney wall, the walls of blood vessels and also the kidney walls.
When the drug starts to reach the intended destination, the process is considered to be diffusion. The diffusion of will make the high concentrated blood vessels to transfer the drug to the required issue until both becomes equal (Pharmacokinetics, 2006). When the tissues have received the maximum concentration of the drug, the drug starts to diminish its affects in the body by it elimination through body as well. This process is different in different drugs which can increase from several minutes to some days as well. The Half Life of drug is determined by observing the elimination time for half its quantity. The half life plays a crucial rule in the determination of the quantity that should be prescribed by the doctor.
The drug molecules can also sometime bind themselves to the proteins. As proteins are heavy, the drug molecules need more time to pass through the cellular barriers. This may increase the half life or the time for which the drug remains in the body but at the same time they will become less effective as well.