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The 30 pages that link to First-pass effect, each with the reason it gives.
PharmacokineticsRelated: It can reduce the fraction of an oral dose reaching systemic circulation.
Drug deliveryRelated: It can reduce the amount of an oral dose reaching the bloodstream.
ProdrugRelated: Some prodrugs exploit metabolism in the gut or liver for activation.
CYP3A4Related: Intestinal and liver CYP3A4 can remove a substantial fraction of some oral doses.
Dosage formRelated: Oral dosage forms can expose drugs to this loss before systemic absorption.
MidazolamRelated: Extensive first-pass metabolism limits oral midazolam bioavailability.