Pharmacokinetics

Pharmacokinetics is the study of the time course of the drug concentration in the body. It is often described as to what the body does to a drug. It is basically the movement of a drug into, through and out of the body.  The drug undergoes series of processes as followed:


L- Liberation
A-     Absorption
D- Distribution
M- Metabolism
E- Excretion

See the video below to understand/review the basic concept of Pharmacokinetics. 

What is LADME system?

As discussed in Review: Pharmacokinetics, a drug after a given dosage regimen undergoes processes which identifies what the body does to a drug. Let’s start with the input processes, Liberation and Absorption.

(L) Liberation is the release of the drug from its dosage form (i.e. tablet, capsule). Solid form drugs must disintegrate first before absorption. Some dosage form by-pass liberation since they can readily be absorbed (i.e. solutions). Take note also that these processes may not happen once after the drug was given. These processes may happen at the same time just like in the case of a sustained release drug. While the previously absorbed drug is being excreted, other parts of the drug is still liberating. I mentioned there absorption, what is it again? (A) Absorption is the movement of the drug from the site of administration to the blood circulation. It is known by identifying the drug’s physicochemical properties, formulation and route of administration.  Remember that a drug must always be in solution before being absorbed. 

After the drug has been absorbed, the output processes (disposition of drug) start. In (D) Distribution process, the drug diffuses to the body’s tissues. This is normally irregular due to difference in blood perfusion and permeability of cell membranes. Not to mention the tissue binding and different pH in different regions.

Following distribution is the drug (M) metabolism. In this event, the drug is transformed into substances that are easily moved out of the body. The principal organ responsible in doing this process is the liver. There are many ways in which the drug can be metabolized.

• Oxidation
• Reduction
• Hydrolysis
• Hydration
• Conjugation
• Condensation
• Isomerization

Finally, the drug undergoes (E) Excretion. It is the elimination of unchanged drug or metabolite from the body. In this course, the kidneys are the main organs responsible. Excretion can be renal, biliary or pulmonary ways.