First Pass Metabolism Flashcards, test questions and answers

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What is First Pass Metabolism?

First-pass metabolism is a term used to describe the process by which drugs or other substances are metabolized by the body and rendered less potent before they reach systemic circulation. The first pass occurs when a drug is ingested and then passes through the gastrointestinal system, liver, and finally into general circulation. During this initial pass, enzymes in the liver can reduce the potency of certain drugs, meaning that only a fraction of what was taken will actually reach systemic circulation. This process can be beneficial because it helps control how much of a given drug may be present in the body at any one time, reducing potential adverse effects. In addition, it can also help protect against overdoses since potentially toxic doses may be reduced before entering general circulation. The amount of first-pass metabolism depends on several factors such as: route of administration (oral vs intravenous), drug properties (lipophilicity), and individual differences in metabolic pathways between individuals due to genetic polymorphisms or other factors such as age, gender or ethnicity. For example, oral bioavailabilitythe amount of active substance that reaches systemic circulationcan vary greatly between individuals due to different levels of first-pass metabolism in their respective livers. Certain drugs are more likely to undergo extensive first-pass metabolism than others; for instance lipophilic compounds tend to have higher levels because they’re more readily absorbed from the gut into enteric cells where they can then be metabolized by cytochrome P450 enzymes before entering general circulation. In conclusion, understanding first-pass metabolism is important when considering pharmacokinetics (PK) and pharmacodynamics (PD). It enables us to predict how much active material will reach systemic circulation after administration and thereby optimize dosage accordingly for each individual patient based on their own unique metabolic makeup. This knowledge also has implications for drug development research as scientists must consider both PK/PD models when designing new treatments so as not to underestimate or overestimate efficacy based on differences in individual metabolic profiles.