Drug metabolism is the chemical alteration of a drug by the body. (See also Introduction to Administration and Kinetics of Drugs.) Some drugs are chemically altered by the body (metabolized).
What happens during drug metabolism?
Excretion involves elimination of the drug from the body, for example, in the urine or bile. Most drugs must pass through the liver, which is the primary site for drug metabolism. Once in the liver, enzymes convert prodrugs to active metabolites or convert active drugs to inactive forms.
How are drugs metabolized in the body?
Drugs can be metabolized by oxidation, reduction, hydrolysis, hydration, conjugation, condensation, or isomerization; whatever the process, the goal is to make the drug easier to excrete. The enzymes involved in metabolism are present in many tissues but generally are more concentrated in the liver.
Why is drug metabolism important?
The metabolism of a drug can have important consequences on its therapeutic effect or its toxicity. For this reason, early assessments of metabolic pathways in man help to foresee interindividual variation in drug response and elimination due to metabolism.
What is Drug Metabolism PDF?
Drug metabolism may be defined as the biochemical modifica- tion of one chemical form to another, occurring usually through specialised enzymatic systems. It often involves the conversion of lipophilic chemical compounds (drugs) into highly polar de- rivatives that can be easily excreted from the body.
What is the difference between a drug and a drug metabolite?
A drug metabolite is a byproduct of the body breaking down, or “metabolizing,” a drug into a different substance. … Therefore, the presence of a drug metabolite can be a reliable indicator that a person used the “parent” drug of that metabolite. Some metabolites stay in the body much longer than the parent drug.
What are the four stages of drug metabolization?
The method by which a drug is administered, along with other factors, determines the speed of onset of effects. Drugs undergo four stages within the body: absorption, distribution, metabolism, and excretion.
What are four classes of drugs?
What types of drug are there?
- stimulants (e.g. cocaine)
- depressants (e.g. alcohol)
- opium-related painkillers (e.g. heroin)
- hallucinogens (e.g. LSD)
How does body weight affect drug doses?
As clearance determines a drug’s maintenance dose, clinicians should consider how lean body weight, rather than total body weight, impacts dosing. When lean body weight increases there will be a corresponding increase in drug clearance and an increased dose may be required.
How does age affect drug metabolism?
Thus, age-related changes in drug metabolism should be considered a typical phenotypic characteristic of the aging process. Generally, older age is associated with increased blood concentrations of drugs and altered metabolism, reduced effectiveness, and increased risk of adverse reactions for many medications (2).
How does genetics affect drug metabolism?
Genetic polymorphisms have been identified for many drug-metabolising enzymes, including the cytochrome P450 (CYP450) enzymes. This gives rise to distinct population phenotypes of persons who have metabolism capabilities ranging from extremely poor to extremely fast.
What is metabolism and what factors affect it?
The amount of kilojoules your body burns at any given time is affected by your metabolism. Your metabolic rate is influenced by many factors – including age, gender, muscle-to-fat ratio, amount of physical activity and hormone function.
What are the two phases of metabolism?
Metabolism is often divided into two phases of biochemical reaction – phase 1 and phase 2. Some drugs may undergo just phase 1 or just phase 2 metabolism, but more often, the drug will undergo phase 1 and then phase 2 sequentially.
What is the purpose of phase 1 metabolism?
Phase I biotransformation reactions introduce or expose functional groups on the drug with the goal of increasing the polarity of the compound. Although Phase I drug metabolism occurs in most tissues, the primary and first pass site of metabolism occurs during hepatic circulation.
What is meant by drug?
A drug is any substance (with the exception of food and water) which, when taken into the body, alters the body’s function either physically and/or psychologically. Drugs may be legal (e.g. alcohol, caffeine and tobacco) or illegal (e.g. cannabis, ecstasy, cocaine and heroin).