According to the Medical dictionary the definition of “Pharmacokinetics is, sometimes abbreviated as PK, the word coming from Ancient Greek pharmakon “drug” and kinetikos “to do with motion,” is a branch of pharmacology dedicated to the determination of the fate of substances administered externally to a living organism. The substances of interest include pharmaceutical agents, hormones, nutrients, and toxins. ” Pharmacokinetics is the study of the rate of drug absorption and disposition in the body.
So, differential calculus is an important part in the development of many of the equations used. There are four pharmacokinetic processes to which every drug is subject in the body: Absorption, Distribution, Metabolism, and Excretion Absorption is the process by which a drug is made available to the fluids of distribution of the body. (i. e. blood or plasma) Most orally-administered drugs reach a maximum or peak level blood concentration within 1-2 hours.
Once a drug has been absorbed from the stomach and/or intestines into the blood, it is circulated to some degree to all areas of the body to which there is blood flow and that is the process of distribution. Metabolism is the complex of physical and chemical processes occurring within a living cell or organism that are necessary for the maintenance of life. In metabolism some substances are broken down to yield energy for vital processes while other substances, necessary for life, are produced.
Drugs are often eliminated by biotransformation, the alteration of a substance within the body, or excretion into the urine or the fluid that is made by the liver, also known as bile. The liver is the major location for drug metabolism, but specific drugs may experience biotransformation in other tissues.
The metabolic transformation of drugs is catalyzed by enzymes, and most of the reactions obey Michaelis-Menten kinetics (a method of transforming drug plasma levels into a linear relationship by using the parameters of drug concentration and a constant, Km, which is a measure of enzyme-substrate affinity.
This is necessary when drug elimination mechanisms are saturable rather than proceeding by first-order kinetics. ) V = rate of drug metabolism = Vmax (C) Excretion is the process by which a drug is eliminated from the body. Differential calculus is a field of calculus that deals with the study of the rates at which an amount changes, it’s involved with the study of rates of processes derivative can be thought of as how much one quantity is changing in response to changes in some other quantity.
The calculus part comes in when we look at the process in detail, that is, during a small time interval. For example, we can say that at time zero a patient has a concentration of 25 ug/ml of a drug in plasma and at 24 hours the concentration is at 5 ug/ml. That can be interesting in its self, but it gives us no idea of the concentration between 0 and 24 hours, or after 24 hours. [pic] Using differential calculus we are able to create equations to look at the process during the small time intervals that make up the total time interval of 0 to 24 hours.
Then we can calculate concentrations at any time after the dose is given to a person. The length of action of a drug is known as its half life. This is the period of time required for the concentration or amount of drug in the body to be reduced by one-half. The half-life of a substance is the time taken for half of the dose to be eliminated or metabolized (Anything an organism does in its body chemically, i. e. if a human eats pasta, the chemical transformation of the body transforming that carbohydrate into sugar.)
The shorter the half-life of a drug, the quicker it gets put out the persons’ system. The half life of a drug can be influenced by many individual factors, such as metabolic, and genetic. [pic] We usually consider the half life of a drug in relation to the amount of the drug in plasma. A drug’s plasma half-life depends on how quickly the drug is eliminated from the plasma. Basically a drug’s plasma is the concentration of the drug in your blood.