What is first pass metabolism of alcohol?
First-pass metabolism of ethanol is observed only after administration of small doses of ethanol, and it is characterized by the difference of the rate of alcohol (= ethanol) elimination occurring after either oral or intravenous application of identical doses of ethanol.
What is a Phase 1 reaction?
Phase I reactions are broadly grouped into three categories, oxidation, reduction, and hydrolysis. As most small molecule drugs are lipophilic in nature, drug metabolism converts these hydrophobic compounds into more water soluble compounds that can be excreted. Typically, oxidation is the most common phase I reaction.
What is phase 1 metabolism?
Phase 1 metabolism involves chemical reactions such as oxidation (most common), reduction and hydrolysis. There are three possible results of phase 1 metabolism. The drug becomes completely inactive. One or more of the metabolites are pharmacologically active, but less so than the original drug.
What is the difference between Phase I and II metabolism?
Phase I reactions of drug metabolism involve oxidation, reduction, or hydrolysis of the parent drug, resulting in its conversion to a more polar molecule. Phase II reactions involve conjugation by coupling the drug or its metabolites to another molecule, such as glucuronidation, acylation, sulfate, or glicine.
What are the 2 phases of drug metabolism?
Drug metabolism reactions comprise of two phases: Phase I (functionalization) reactions such as oxidation, hydrolysis; and Phase II (conjugation) reactions such as glucuronidation, sulphate conjugation.
What are 2 phases of metabolism?
Metabolism is often divided into two phases of biochemical reaction – phase 1 and phase 2.
Where does Phase 1 and 2 metabolism occur?
The liver is the primary site for metabolism. Liver contains the necessary enzymes for metabolism of drugs and other xenobiotics. These enzymes induce two metabolism pathways: Phase I (functionalization reactions) and Phase II (biosynthetic reactions) metabolism.
What are the three phases of metabolism?
The metabolism of xenobiotics is often divided into three phases:- modification, conjugation, and excretion.
How does polarity affect metabolism?
Metabolism is the enzymatic conversion of one chemical compound into another. Overall, metabolic processes will convert the drug into a more water-soluble compound by increasing its polarity. This is an essential step before the drug can be excreted in the body fluids such as urine or bile.
What is second pass metabolism?
After a drug is swallowed, it is absorbed by the digestive system and enters the hepatic portal system. However, significant hepatic extraction still occurs because of second pass metabolism, whereby a fraction of venous blood travels through the hepatic portal vein and hepatocytes.
How do you know if you are a poor metabolizer?
Poor metabolizer: Patients who are poor metabolizers experience a very slow breakdown of medications, making side effects more pronounced. That means standard doses of certain medications may not work as intended.
Which three genetic variations in enzymes are most often linked to differences in drug metabolism?
Among them, CYP2C9*2 (R144C) and CYP2C9*3 (I359L) are the most common variants associated with highly-reduced CYP2C9 enzymatic activities in comparison with the wild-type allele (CYP2C9*1) .
How does CYP2C19 affect metabolism?
Most often, changes in the CYP2C19 gene lead to impaired metabolism of these drugs, which reduces their effectiveness. One change in the CYP2C19 gene (known as CYP2C19*17) increases the enzyme’s ability to metabolize drugs.
What factors affect metabolism of a drug?
Individual drug metabolism rates are influenced by genetic factors, coexisting disorders (particularly chronic liver disorders and advanced heart failure), and drug interactions (especially those involving induction or inhibition of metabolism). For many drugs, metabolism occurs in 2 phases.
Why dont drugs affect me as much as others?
Individuals who do not respond to medications as expected may have genetic differences that change the amount of enzymes available to break down a medication or may cause the enzymes not to work. These genetic differences may have an effect on how someone responds to a medication.
How long after eating is your stomach considered empty?
The F.D.A. defines an empty stomach as “one hour before eating, or two hours after eating.” The F.D.A.’s two-hour rule is just a rule of thumb; the stomach will probably not be completely empty. The specific definition of an empty stomach varies from drug to drug.