Exam 1- lectures 5,6,&7 Flashcards
PM
poor metabolizers
EM
extensive metabolizers
What phase of metabolism are CYP enzymes?
Phase I
what phase of metabolism are NAT, UGT & GST?
Phase II
CYP450 oxidizes drugs by adding:
an -OH group
CYP4 is mainly used for
lipid metabolism
CUP1A2
caffeine, melatonin, theophylline
CYP2A6
Coumarin, Nicotine
CYP2B6
buproprion, efavirenz, S-mephenytoin
CYP2C8
paclitaxel, pioglittazone
CYP2C19
omeprazole, S-mephenytoin
CYP2D6
dextromethorphan, debrisoquine, metoprolol
CYP3A
midazoleam, cortisol
CYP3A4
- largest form expressed in the liver
- metabolizes 45-60%
- NO grapefruit juice
- 18 variants
- erythromycin, nifedipine, cyclosporin, midazolam
CYP2C9
- 20% of liver P450
- warfarin, phenytoin, losartan, fluvastain, NSAIDs
- 2 major variants
- mainly caucasians
CYP2C9*2
cys 144 instead of Arg 144; fairly small effects
CYP2C9*3
leu 359 instead of Ile 359; pronounced reduction in catalytic activity; PM
CYP2C19
- S-mephenytoin
- 9 variants
- many drugs are metabolized by other P450
- Caucasians lowest
- chinese highest
CYP2D6
- PM autosomal recessive- so need to be homo
- 4 groups of metabolizers
- debrisoquine- dextromethorphan, codeine, oxycodone, TCAs, SSRIs, beta blockers
phase I enzymes convert drug to what form?
may be active or inactive
phase II enzymes convert drug to what form?
usually inactive
phase II drugs
improve drugs water solubility & prepare it for elimination
glucuronyl transferase (UGT) MOA
- takes UDP-glucuronic acid & transfers the sugar group to drug
- conjugates bilirubin
- imp. for NSAIDs & tylenol & inrinotecan
crigler-najjar disease
deficiency of UGTA1 & leads to jaundice
gilbert’s syndrome
associated with UGT1A1 deficiency
- compromised bilirubin elimination
UGT1A6 deficiency
can lead to acetominophen sensitivity
glutathione-S-Transferase (GST)
- conjugates drugs through formation of thioester linkage
- highly expressed in liver
- 4 classes: A,M,P,T
N-Acetyl Transferase (NAT)
- acetylators
where is NAT1 found?
in most tissues
where is NAT2 found?
in liver & gut
significant polymorphisms
wild type NAT
probably rapid acetylatos
isoniazid-phenytoin interaction
slow acetylators show higher [] of isoniazid which inhibits hydroxylationof phenytoin, increasing its []->toxicity
PM effects
- < first pass metabolism
- > oral bioavailability
- < metabolic clearance
- > half life
- > drug effects & toxicity
- < metabolits
- possible inhibition of metabolism of other drugs
ultra-rapid metabolizer effetcs
- > first pass metabolism
- < oral bioavailibility
- > metabolic clearance
- < half life
- < therapeutic effects
- > metabolites
GPCRs
beta adrenergic receptor, serotonin receptor, mu-opiod receptor (beta-blockers, antipsycotics/antidepressants, opioid analgesics)
Transporters & ion channels
sodium channel, K channel, serotonin transporter (antiarrhythmics, antipsycotics/antidepressents)
nuclear hormone receptors
estrogen receptor, androgen receptor, glucocorticoid receptor (hormone therapy, glucocorticoids)
enzymes
angiotensin converting enzyme (ACE),(ACEI)
beta-agonist
reactive airway disease
beta-blockers
cardiovascular disease
beta 1
heart
beta 2
lungs
enhanced receptor down regulation in response to beta2 agonist
less efficacy
resistant to receptor down regulation
better efficacy
reduced affinity for some beta2 agonist
less binding, less efficacy
activatio of 5-LOX receptor produces:
leukotrienes
decreased expression of ALOX5
less responsive to leukotriene inhibitors-> disease not mediated by leukotrienes
increased expression of ALOX5
more responsive to leukotriene inhibitors->leukotrienes play a major role in disease
what is clozapine used to treat and where does it act?
acts on 5-HT2A receptors to treat schizophrenia
mutation in 5-HT2A receptor
his->Tyr
side effects of clozapine
agranulocytosis, seizures, mycarditis
CYP2D6 role in opioids
codeine->morphine (active)
UGT role in opioids
morphine->metabolites
QT prolongation risk factors
female, concomitant meds, long QT syndrome (LQTS)- mutations in various ion channels
LQT1
potassium ion
most common
LQT2
potassium ion
second most common
drug induced
LQT3
sodium ion
LQT5 &6
potassium ion
rare
LQT1&2 treatment
K supplementation & K channel openers
LQT3 treatment
Na channel openers
abacavir genotype
HLA-B*5701 (MCH class I) can be fatal
carbamazepine genotype
HLA-B*1502
stevens-johnson syndrome
can be fatal
allopurinol genotype
HLA-B*5801