First-Pass Metabolism: Difference between revisions
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First-pass metabolism (also known as presystemic metabolism) refers to the action of metabolic enzymes, in the liver and gut wall, on drugs.<ref>Rang H, Dale M, Ritter J, Flower R and Henderson G. (2012) Rang and Dale's Pharmacology, 7th Edition, Spain: Elsevier Inc.</ref>These enzymes metabolise drugs before they enter the systemic circulation, often rendering a fraction of the drug inactive.<ref name="null">Rang H, Dale M, Ritter J, Flower R and Henderson G. (2012) Rang and Dale's Pharmacology, 7th Edition, Spain: Elsevier Inc.</ref> This lowers the proportion of an ingested drug that is acquired by the systemic circulation in its active form (its bioavailability).<ref>Rang H, Dale M, Ritter J, Flower R and Henderson G. (2012) Rang and Dale's Pharmacology, 7th Edition, Spain: Elsevier Inc</ref | First-pass metabolism (also known as presystemic metabolism) refers to the action of metabolic [[Enzyme|enzymes]], in the liver and gut wall, on drugs.<ref>Rang H, Dale M, Ritter J, Flower R and Henderson G. (2012) Rang and Dale's Pharmacology, 7th Edition, Spain: Elsevier Inc.</ref>These enzymes metabolise drugs before they enter the [[Systemic Circulation|systemic circulation<span id="fck_dom_range_temp_1321292465940_626" />]], often rendering a fraction of the drug inactive.<ref name="null">Rang H, Dale M, Ritter J, Flower R and Henderson G. (2012) Rang and Dale's Pharmacology, 7th Edition, Spain: Elsevier Inc.</ref> This lowers the proportion of an ingested drug that is acquired by the systemic circulation in its active form (its [[Bioavailability|bioavailability]]).<ref>Rang H, Dale M, Ritter J, Flower R and Henderson G. (2012) Rang and Dale's Pharmacology, 7th Edition, Spain: Elsevier Inc</ref> | ||
This form of metabolism is therapeutically relevant as... | This form of metabolism is therapeutically relevant as... | ||
1) It implies that the efficacy of a drug is lower when its route of administration is oral rather than intravenous. <ref name="null">Grahame-Smith D, Aronson J. (2002) Oxford Textbook of Clinical Pharmacology and Drug Therapy, 3rd Edition, Hong Kong: Oxford University Press.</ref>This frequently means that a higher dose is used when a drug is administered orally.<ref name="null">Rang H, Dale M, Ritter J, Flower R and Henderson G. (2012) Rang and Dale's Pharmacology, 7th Edition, Spain: Elsevier Inc.</ref> First-pass metabolism can reduce the bioavailability of some drugs to the extent that it renders them completely ineffective and | 1) It implies that the [[Drug Efficacy|efficacy]] of a drug is lower when its route of administration is oral rather than intravenous. <ref name="null">Grahame-Smith D, Aronson J. (2002) Oxford Textbook of Clinical Pharmacology and Drug Therapy, 3rd Edition, Hong Kong: Oxford University Press.</ref>This frequently means that a higher dose is used when a drug is administered orally.<ref name="null">Rang H, Dale M, Ritter J, Flower R and Henderson G. (2012) Rang and Dale's Pharmacology, 7th Edition, Spain: Elsevier Inc.</ref> First-pass metabolism can reduce the bioavailability of some drugs to the extent that it renders them completely ineffective and makes oral administration unsuitable ([[Insulin|insulin]] is an example of this).<ref>Grahame-Smith D, Aronson J. (2002) Oxford Textbook of Clinical Pharmacology and Drug Therapy, 3rd Edition, Hong Kong: Oxford University Press.</ref> | ||
2) First-Pass Metabolism differs between people. <ref>Rang H, Dale M, Ritter J, Flower R and Henderson G. (2012) Rang and Dale's Pharmacology, 7th Edition, Spain: Elsevier Inc.</ref> | 2) First-Pass Metabolism differs between people. <ref>Rang H, Dale M, Ritter J, Flower R and Henderson G. (2012) Rang and Dale's Pharmacology, 7th Edition, Spain: Elsevier Inc.</ref> | ||
Revision as of 17:43, 14 November 2011
First-pass metabolism (also known as presystemic metabolism) refers to the action of metabolic enzymes, in the liver and gut wall, on drugs.[1]These enzymes metabolise drugs before they enter the systemic circulation, often rendering a fraction of the drug inactive.[2] This lowers the proportion of an ingested drug that is acquired by the systemic circulation in its active form (its bioavailability).[3]
This form of metabolism is therapeutically relevant as...
1) It implies that the efficacy of a drug is lower when its route of administration is oral rather than intravenous. [2]This frequently means that a higher dose is used when a drug is administered orally.[2] First-pass metabolism can reduce the bioavailability of some drugs to the extent that it renders them completely ineffective and makes oral administration unsuitable (insulin is an example of this).[4]
2) First-Pass Metabolism differs between people. [5]
- ↑ Rang H, Dale M, Ritter J, Flower R and Henderson G. (2012) Rang and Dale's Pharmacology, 7th Edition, Spain: Elsevier Inc.
- ↑ 2.0 2.1 2.2 Rang H, Dale M, Ritter J, Flower R and Henderson G. (2012) Rang and Dale's Pharmacology, 7th Edition, Spain: Elsevier Inc. Cite error: Invalid
<ref>tag; name "null" defined multiple times with different content - ↑ Rang H, Dale M, Ritter J, Flower R and Henderson G. (2012) Rang and Dale's Pharmacology, 7th Edition, Spain: Elsevier Inc
- ↑ Grahame-Smith D, Aronson J. (2002) Oxford Textbook of Clinical Pharmacology and Drug Therapy, 3rd Edition, Hong Kong: Oxford University Press.
- ↑ Rang H, Dale M, Ritter J, Flower R and Henderson G. (2012) Rang and Dale's Pharmacology, 7th Edition, Spain: Elsevier Inc.