lisäaineenvaihdunnalla

Lisäaineenvaihdunnalla, known in English as drug metabolism, refers to the biochemical processes that modify xenobiotics, particularly drugs. This process occurs primarily in the liver but also in other tissues like the intestines, kidneys, and lungs. The main goal of drug metabolism is to make lipophilic (fat-soluble) drugs more hydrophilic (water-soluble), facilitating their excretion from the body, mainly through urine or bile.

Drug metabolism can be broadly divided into two phases. Phase I reactions, often called functionalization reactions, introduce or expose polar functional groups onto the drug molecule. Common Phase I reactions include oxidation, reduction, and hydrolysis, catalyzed by enzymes such as the cytochrome P450 (CYP) superfamily. These reactions can sometimes lead to the formation of active metabolites, which may have pharmacological activity themselves or be more toxic than the parent drug.

Phase II reactions, also known as conjugation reactions, involve the attachment of an endogenous, polar molecule to the drug or its Phase I metabolite. Examples of these conjugations include glucuronidation, sulfation, acetylation, and methylation. These reactions further increase the water solubility of the compound, making it readily excretable.

The rate and pathways of drug metabolism can vary significantly between individuals due to genetic factors, age, disease states, and interactions with other drugs or substances. This variability is a key reason why drug dosages often need to be individualized to achieve optimal therapeutic effects and minimize adverse reactions. Understanding drug metabolism is crucial for pharmacology, toxicology, and drug development.