What is Pharmacokinetics
Pharmacokinetics is the branch of pharmacology which deals with determining the movement (kinetics) of drugs into and out of the body. Experimentally, this is done by administering the drug to a group of volunteer subjects or patients and obtaining blood and urine specimens for subsequent quantitative (how much) analysis. When the results of these analyses are plotted on graph paper with blood levels or urinary excretion on the verticle axis and time on the horizontal axis, a blood level-time or urinary excretion pattern is obtained.
There are four scientific or pharmacokinetic processes to which every drug is subject in the body:
Absorption
Absorption is the process by which a drug is made available to the fluids of distribution of the body (e.g., blood, plasma, serum, aqueous humor, lymph, etc.).
In the fasting state, most orally-administered drugs reach a maximum or "peak" blood concentration within 1-2 hours. Intravenous (IV) administration is the most rapid route of administration, with intra-nasal, smoking (inhalation), sub lingual (under the tongue), intra-muscular (IM), subcutaneous (e.g., under the skin)
Distribution
Once a drug has been absorbed from the stomach and/or intestines (GI Tract) into the blood, it is circulated to some degree to all areas of the body to which there is blood flow. This is the process of distribution. Organs with high blood flow e.g., brain, heart, liver, etc. are the first to accumulate drugs, while connective tissue and lesser perused organs are the last.
Metabolism
Drugs in the blood and tissues must be inactivated and excreted from the body. This process is initiated by altering the chemical structure of the drug in such a way as to promote its excretion. The transformation of the drug molecule into a chemically related substance that is more easily excreted from the body is called metabolism, biotransformation or detoxification.
Therapeutic agents like antibiotics and drugs used for the treatment of high blood pressure, epilepsy (e.g., phenobarbital, Dilantin), pain (e.g., morphine, codeine), anxiety (e.g., Valium, Xanax) are also metabolized to chemically-related compounds called metabolites, which are then excreted in the urine
Excretion
Excretion is the process by which a drug is eliminated from the body.
Drugs can be excreted by various organs including the kidney and lungs, and found in many biological fluids like: bile, sweat, hair, breast milk, or tears. However, the most common fluid in which to look for drugs is the urine.
Pharmacokinetics is the branch of pharmacology which deals with determining the movement (kinetics) of drugs into and out of the body. Experimentally, this is done by administering the drug to a group of volunteer subjects or patients and obtaining blood and urine specimens for subsequent quantitative (how much) analysis. When the results of these analyses are plotted on graph paper with blood levels or urinary excretion on the verticle axis and time on the horizontal axis, a blood level-time or urinary excretion pattern is obtained.
There are four scientific or pharmacokinetic processes to which every drug is subject in the body:
- Absorption
- Distribution
- Metabolism
- Excretion
Absorption
Absorption is the process by which a drug is made available to the fluids of distribution of the body (e.g., blood, plasma, serum, aqueous humor, lymph, etc.).
In the fasting state, most orally-administered drugs reach a maximum or "peak" blood concentration within 1-2 hours. Intravenous (IV) administration is the most rapid route of administration, with intra-nasal, smoking (inhalation), sub lingual (under the tongue), intra-muscular (IM), subcutaneous (e.g., under the skin)
Distribution
Once a drug has been absorbed from the stomach and/or intestines (GI Tract) into the blood, it is circulated to some degree to all areas of the body to which there is blood flow. This is the process of distribution. Organs with high blood flow e.g., brain, heart, liver, etc. are the first to accumulate drugs, while connective tissue and lesser perused organs are the last.
Metabolism
Drugs in the blood and tissues must be inactivated and excreted from the body. This process is initiated by altering the chemical structure of the drug in such a way as to promote its excretion. The transformation of the drug molecule into a chemically related substance that is more easily excreted from the body is called metabolism, biotransformation or detoxification.
Therapeutic agents like antibiotics and drugs used for the treatment of high blood pressure, epilepsy (e.g., phenobarbital, Dilantin), pain (e.g., morphine, codeine), anxiety (e.g., Valium, Xanax) are also metabolized to chemically-related compounds called metabolites, which are then excreted in the urine
Excretion
Excretion is the process by which a drug is eliminated from the body.
Drugs can be excreted by various organs including the kidney and lungs, and found in many biological fluids like: bile, sweat, hair, breast milk, or tears. However, the most common fluid in which to look for drugs is the urine.