What Is drug ADME (Absorption, Distribution, Metabolism, and Excretion)?

Drug ADME (Absorption, Distribution, Metabolism, and Excretion) are primary steps the human body handles a drug in the body.

Step 1. Drug absorption: This is how the drug enters the blood -- usually from tablets or capsules in the stomach and intestines. For some drugs, the amount of acid in the stomach, or the amount of food in the stomach, really changes the amount of drug that is absorbed. This is the reason that some drugs have "food requirements", or why some drugs have warnings not to take antacids along with the drug.

Step 2. Drug distribution: This is how the drug travels in the bloodstream and how it goes into and comes out of other areas of the body. Some areas of the body, like the brain and reproductive organs, are specially protected from chemicals (including drugs).

Step 3. Drug metabolism: This is how the body chemically changes a drug -- usually in the intestines and liver. Metabolism involves breaking a drug down or adding a chemical that makes it easier to pass it into urine or stool. A lot of drug-drug interactions happen because one drug interferes with the metabolism of another drug (called inhibition). Inhibition causes higher drug levels. On the other hand, a drug can also speed up the metabolism of another drug (called induction). Induction causes lower drug levels.

The CYP-450 (pronounced "sip") enzyme system is a well-known group of human enzymes that metabolize drugs and chemicals in the body. CYP-450 enzymes are mostly in the intestines and liver.

Step 4. Drug elimination: This is how the body gets the drug out -- usually by passing the drug into the urine (via the kidneys) or stool (via the liver). Sometimes people have some kidney or liver illness. In these people, the blood level of some drugs may build to very high levels if the drug dose is not reduced.

 

⇒ List of PK (Pharmacokinetics) Symbols

⇐ What Are PK Related Terminologies

⇑ PK/PD Basic Concepts

⇑⇑ PK/PD Tutorials