Pharmacokinetics: Drug Absorption to Excretion

Absorption and Distribution

• A drug enters the body through administration, which can be oral, parenteral, or topical
• The drug dissolves or disperses in a solvent (such as water or lipid) at the site of administration
• The drug is then absorbed into the bloodstream through diffusion or active transport
• The absorbed drug is distributed throughout the body via the circulatory system
• Drug distribution is influenced by factors such as blood flow, membrane permeability, and protein binding

Metabolism

• The drug is carried to the liver, where it is metabolized by enzymes
• Metabolism involves the conversion of the drug into a more water-soluble metabolite
• The liver is the primary site of metabolism, but other tissues such as the kidneys and lungs can also metabolize drugs
• Metabolism can inactivate the drug, convert it to an active form, or produce toxic compounds

Bioavailability

• Bioavailability refers to the fraction of the administered dose that reaches the systemic circulation
• Bioavailability is affected by factors such as absorption, distribution, and metabolism

Site of Action

• The drug reaches its site of action, where it interacts with target molecules (such as receptors, enzymes, or transporters)
• The drug binds to its target molecule, leading to a response or effect

Elimination

• The drug is eliminated from the body through excretion, which can occur through the kidneys, liver, or lungs
• The kidneys excrete the drug through urine, while the liver excretes the drug through bile
• The drug is eliminated in its original form or as a metabolite

Understand the journey of a drug from administration to its site of action and finally excretion. Learn about the pharmacokinetic processes that occur in the body.