Once the drug is administered, the Phamacokinetic phase or absorption begins. The route of administration, the solubility of the drug and the presence of inflammation influence the rate of absorption. Intravenous administration is the fastest, while oral injection is the slower. Water soluble drugs are absorbed more quickly.
The Phamacokinetic phase continues with the distribution of the drug. For a drug to be therapeutic a sufficient amount of the drug must be available in the system. Too much of the drug may cause a toxic effect, while too little will not do what it is suppose to do.
The next step in the Phamacokinetic phase is metabolism or biotransformation. Metabolism most often occurs in the liver. But may also occur in the kidneys, lungs, plasma and intestinal mucosa.
Lastly, the final phase of the Phamacokinetic process is excretion. Most often excretion occurs my the kidneys in urine. But drugs may also be eliminated through sweat, saliva, bile, breast milk, breathing and feces.
As discussed in the text, there are numerous factors that influence the effects of drugs. An example is an individual with uncontrolled diabetes and periodontal disease. An individual with uncontrolled diabetes is at higher risk for periodontal disease due to the body's decreased ability to effectively respond to inflammation. However, the therapeutic effect of insulin is decreased in the presence of inflammation. As you can imagine, without careful monitoring of the circulating drug, resolution of both diseases may be challenging.
The Phamacokinetic Phase is very clearly illustrated in these animations: