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36 Cards in this Set

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  • Back
Define Phase I reactions
modify the chemical structure ofa drug through oxidation, reduction or hydrolysis
Define Phase II reactions
conjugate a drug to large polar molecules in order to inactivate the drug, or more commonly, to enhance the drug's solubility and excretion rate in the urine or bile
What are the most commonly added groups during phase II reactions?
- glucuronate
- sulfate
- glutathione
- acetate
What percentage of total systemic blood flow goes to the kidnies?
What is the drug concentration in the proximal tubule?
high. there are similarities between drugs and organic acids and bases, which are secreted.
What happens to the urinary conecntration of a drug in the proxima and distal tubule?
it falls. reabsorption is limited by pH trapping.
how is aspirin overdose treated?
by giving sodium bicarbonate to make the urin more basic. aspirn is a weak acid that is excreted renally. changing the pH traps aspirin in the tubule
give examples of drugs excreted in the bile
cancer chemotherapeutics
what is saquinavir?
a protease inhibitor
what do phase I reactions do?
expose or add polar functional groups such as
- OH
- SH
- NH2
what does lidocaine do?
antiarrhythmic. must be given IV (first pass effect too severe)
what other organ can induce first pass effects?
the GI tract
where are the phase I reaction enzymes found?
membrane of the ER of hepatocytes
what times of enzymes catalyze phase I reactions:
hemeprotein monooxygenases of the cytochrome P450 class
what does succinylcholine do?
muscle relaxant
when can you start carrying out phase II reactions?
after the first 2 weeks of life
what causes neonatal jaundice?
deficiency in phase II enzyme UDP-GT
what does grapefruit juice do?
it has psoralen derivatives and flavonoids that inhibit the CYP3A4 isozyme in the samll intestine, and thereby decrease the first-pass metabolism
what type of drug drug interaction can compromise the efficacy of OCPs?
certain antibiotics, such as rifampin
give an example of competitive substrate inhibition in drug interactions
warfarin (anticoagulant) with tamoxifen (a selective estrogen receptor modulator). They both compete for CYP3A4
how does aspirin work?
irreversibly acetylates cyclooxygenase.
how is drug metabolism affected by hyperthyroidism?
possibly increased
Give the equation for Phase I reactions
Drug + O2 + NADPH + H --> Drug-OH + H2O + NADP+
What does CYP mean?
its the family of cytochrome P450 enzymes
where do most P450 phase I reactions take place?
in the ER membrane of hepatocytes
what is an important non-P450 phase I enzyme?
MAO (monoamine oxidase)
- oxidizes amine-containing compounds like catecholamines and tyramine
a monoamine compound derived from the amino acid tyrosine.
- Tyramine plays a significant part in causing hangovers and their headaches. It occurs in particularly high levels in red wine.
- in humans, if monoamine metabolism is compromised by the use of monoamine oxidase inhibitors (MAOIs) and foods high in tyramine are ingested, a hypertensive crisis can result as tyramine can cause the release of stored monoamines, such as norepinephrine, epinephrine and serotonin. The first signs of this were discovered by a neurologist who noticed his wife, who at the time was on MAOI medication, had severe headaches when eating cheese. For this reason, the crisis is still called the "cheese syndrome," even though other foods can cause the same problem.
what types of moieties do you need for the congugation reaction in phase II reactions?
- hydroxyl
- amine
- carboxyl
where do phase II reactions take place?
- cytosol and ER of hepatocytes
what is phase II enzyme UDP-glycurunyl transferase (UDP-GT) responsible for?
conjugating bilirubin in the liver
how do you treat kernicterus?
with barbiturate phenobarbital
what is carbamazepine
an antiepileptic
what catalyzes the transformation bnetween Levodopa to dopamine?
DOPA decarboxylase
how is acetaminophen metabolized?
primariy by phase II mediated glucuronidation and sulfation
describe acetaminophen overdose
- glucuronidation and sulfation pathways are saturated
- glutathione stores in liver are depleted
- build up of reactive intermediate: N-acetyl benzoquinoneimine
what is cimetidine used for?
a histamine-2 receptor antagonist and a potent inhibitor of P450 enzymes