Pharmacokinetics is the area of health sciences that studies the path taken and the impact caused by the medicines (drugs) in the human body. The main object of study of pharmacokinetics is the drug metabolism process.
The analysis of the processes of absorption, biotransformation, bioavailability and excretion of drugs is part of this study. The analysis is important for the prescription of medications to be done in a safe way, with regard to quantities, doses, form of administration and evaluation of side effects.
Stages of Pharmacokinetics
Absorption
Absorption is the process that begins with the application or taking of the drug until it enters the bloodstream. The assessment of the form of absorption is essential for the effects of the medication to be satisfactory.
Absorption can occur through different routes, according to the indication for each case: oral, rectal, cutaneous, intramuscular, respiratory, subcutaneous and intraperitoneal.
Some health conditions and physiology can influence the proper absorption of the active ingredient of a medicine, such as inflammatory processes, blood flow, menstruation and applied dosage.
Biotransformation
Biotransformation is the step in which the medication is transformed into an aqueous compound. Biotransformation is an important phase to ensure the excretion of medication residues, which takes place in the liver.
Bioavailability
Bioavailability is the portion of the medication that reaches the bloodstream. The value is close to 100% when the medication is administered intravenously. Other routes of application tend to have a lower bioavailability.
The assessment of bioavailability is important for deciding on the proper application of drug doses.
Excretion
Excretion is the way and speed with which medication residues are released from the body. The speed depends on the type of medication, the filtration process in the body and the renal flow of each person. Remnants of medications can be eliminated by urine, feces, liver, saliva, kidneys, sweat, among others.
Pharmacokinetics and pharmacodynamics
Pharmacokinetics should not be confused with pharmacodynamics. While pharmacokinetics studies the path taken by medication in the body, pharmacodynamics studies the mechanism of action and physiological effects caused by the active principles that make up a remedy.
See also the meaning of Pharmacodynamics and Metabolism.