The study of the movement of the drug throughout body is called pharmacokinetics studies. These studies are done in the early phase of the drug discovery stage. In simple terms it is the study of absorption, distribution, metabolism, and excretion of the drug in the body.
What is the need for Pharmacokinetic studis in Drug Discovery?
- Predict Human Kinetics – The primary purpose of PK studies is to validate the tools that will be used to predict human kinetics. This data helps the scientists understand the flaws of the drug design and helps them rectify them at an earlier stage.
- Assess the Half Life – The total amount of time taken for the construction of the drug to reach 50% in the plasma or the total amount in the body is called Half Life. The half life of Paracetamol is 4 to 5 hours in the plasma.
- Bioavailability (BA or F) – It is a subcategory of absorption and also a measurement of the rate and extent to which a drug reaches at the site of action, is also the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. Drugs that are injected into the vein has 100% percent BA.
- Clearance – It is the measurement of the volume of plasma from which a substance is completely removed per unit time.
Mathematically clearance is expressed as
Clarence = Renal clearance + Hepatic clearance + Lung clearance
It can refer to the amount of drug removed from the whole body per unit time (mL/min), or in some cases the inter-compartmental clearances can be discussed referring to redistribution between body compartments such as plasma, muscle and fat.
- Volume of distribution (VD) – It is defined as the distribution of the drug between the blood plasma and the whole body. It is the theoretical volume that would be necessary to contain the total amount of an administered drug at the same concentration that it is observed in the blood plasma.