Drug disposition

Drug disposition


Drug disposition refers to the processes by which a drug is absorbed, distributed, metabolized, and eliminated by the body. These processes collectively determine the concentration of the drug at its site of action and ultimately influence its therapeutic effects and potential side effects. Here are the key components of drug disposition:

 

1. Absorption:

   - Absorption is the process by which a drug enters the bloodstream from its site of administration (e.g., oral, intravenous, topical).

   - Factors affecting drug absorption include the route of administration, drug formulation, gastrointestinal motility, and the presence of food or other substances in the stomach.

 

2. Distribution:

   - Distribution refers to the movement of a drug throughout the body, from the bloodstream to various tissues and organs.

   - Drug distribution is influenced by factors such as blood flow to tissues, drug protein binding, tissue permeability, and the presence of barriers like the blood-brain barrier.

 

3. Metabolism (Biotransformation):

   - Metabolism involves the chemical transformation of a drug into metabolites, usually in the liver or other tissues.

   - Drug metabolism can lead to the activation or inactivation of drugs and is primarily mediated by enzymes such as cytochrome P450 enzymes.

 

4. Elimination (Excretion):

   - Elimination is the removal of a drug or its metabolites from the body, primarily through urine, feces, breath, or sweat.

   - The major routes of drug elimination include renal (kidneys), hepatic (liver), biliary (bile), and pulmonary (lungs) excretion.

 

Factors influencing drug disposition include age, genetics, organ function (e.g., liver and kidney function), drug-drug interactions, and disease states. Understanding drug disposition is crucial in pharmacokinetics, the study of how drugs move through the body, as it helps optimize drug dosing, predict drug effects, and minimize adverse reactions.

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