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The process by which a drug leaves the blood stream and enters the extracellular fluid and/or the cells of the tissues
Acidic drugs bind to _____ (protein) and basic drugs to _____ (protein).
How can maternal sulfonamides increase the risk of bilirubin encephalopathy in the newborn?
sulfonamides displace unconjugated bilirubin from albumin
What type of drugs are associated with redistribution?
highly liposoluble drugs administered rapidly by IV injection or inhalation
Explain why lipophilic compounds are not easily excreted.
lipophilic compounds are reabsorbed through the tubular membranes
List 2 processes that are often involved in the activation of prodrugs.
hydrolysis of an ester
hydrolysis of amide linkage
What are the 2 most active drug-metabolizing centers within a given cell?
ER (phase 1)
cytosol (phase 2)
What is the main enzyme system responsible for phase 1 reactions?
cytochrome P450 system
- superfamily of heme proteins present in bacteria, fungi, insects, plants, fish, and mammals
Cytochrome P450 general reaction
- the reaction is a monooxygenation
- the enzyme is a monooxygenase because it incorporates only one of the two oxygen atoms into the substrate
What form of the cytochrome P450 heme iron is required to metabolize drugs?
reduced to the ferrous state (Fe2+)
List 3 drugs that are typical inducers of the cytochrome P450 system.
- P450 enzyme induction typically occurs via increased transcription
List the 3 xenobiotic receptors.
aryl hydrocarbon receptor (AhR)
pregnane X receptor (PXR)
constitutively active receptor (CAR)
AhR inducers (2) and gene targets (3)
polycyclic aromatic hydrocarbons
List 2 important clinical consequences of enzyme induction.
a drug can increase its own metabolism
a drug can increase the metabolism of a coadministered drug
What is the function of multi-drug resistance protein 1 (P-glycoprotein)?
actively transports compounds back into the intestinal lumen
What xenobiotic receptor transcriptionally regulates MDR1?
- drugs that induce P450 enzymes via the PXR pathway also induce MDR1 (protective)
Acetaminophen overdose antidote
- supplies cysteine for glutathione production
- mops up NAPQI
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