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1
Q

1st order kinetics does high dose have a higher half life

A

no. half life and dose is independent. half life is a constant

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2
Q

what is the relationship between dose and plasma concentration? (1st order)

A

they are proportional, high dose will have a high plasma conc.

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3
Q

what is the effect of concentration on the rate of elimination? (1st order)

A

the plasma concentration is proportional to rate of elimination. the high the dose, the higher the plasma conc the faster the rate of elimination

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4
Q

what is the relationship between volume of distribution Vd and peak plasma concentration?

A

the lower the volume of distribution, the higher peak plasma concentration. Vd=Dose/Initial plasma conc.

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5
Q

what is the relationship between rate of elimination of the drugs with different volume of Vd?

A

the higher the Vd,the slower the rate of elimination.

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6
Q

explain how Vd affects half life of a drug?

A
  1. Vd is an apparent volume into which the drug appears to distribute to achieve a given conc. in the plasma
  2. the higher the Vd, the greater the proportions of drug that is distributed outside of the blood stream.
  3. thus, less in plasma and therefore, elimination proceeds at a slower rate giving a longer half life.
    Vd is proportional to half life.
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7
Q

did dose affect the time for plasma conc. to fall to T1/2?

A

no

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8
Q

did Vd affect the time for plasma conc to fall to T1/2

A

yes

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9
Q

did clearance affect the time for plasma conc to fall to T1/2

A

yes

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10
Q

which parameter that T1/2 is dependent on?

A

Vd and Cl

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11
Q

which parameter that T1/2 is independent on?

A

DOSE

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12
Q

give a equation on T1/2 and Vd and Cl

A

T1/2= 0.693 x Vd/Cl

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13
Q

is clearance dependent on initial plasma conc.

A

no. independent

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14
Q

when is the rate of elimination fastest

A

first order kinetics

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15
Q

when is the rate of elimination slowest

A

when plasma conc. is lowest

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16
Q

when is the rate of elimination constant

A

always linear in 0 order kinetics, until the elimination enzyme is no longer saturated

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17
Q

can you determine the half life of 0 order kinetics

A

no. the time for plasma conc. to fall by 1/2 depends on conc. its no possible to determine

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18
Q

what is the relationship between rate of elimination and clearance ?

A

they are proportional, i.e. the slower the clearance the slower the rate of elimination.

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19
Q

for the i.v. bolus injection, why the decling phase is exponential? does it reach 0 eventually?

A

the concentration of the drug affect the rate of elimination. it will reach 0 eventually

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20
Q

if a drug is giving i.v infusion, what shape is the curve

A

the plasma concentration increases and reach plateau

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21
Q

if a drug is giving i.v infusion, why it plateau at the end

A

the rate of accumulation = the rate of elimination

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22
Q

what shape is i.v bolus ?

A

exponential decay

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23
Q

what shape is single oral dose

A

the Cp increases and reach plateau and then decrease

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24
Q

what shape is i.v bolus injection, saturable elimination

A

the plasma is at peak at the beginning and follow the 0 order kinetics. the Cp decreases linearly. when the enzyme is no longer saturated, it will decrease exponentially due to 1st order kinetics.

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25
oral dose. what is rising, decline phase represent for? and plateau phase?
rising phase: the elimination is slower than absorption rate decline: elimination is higher than absoption rate plateau: elimination is equal to absorption rate
26
what is CYP3A4?
the major CYP in liver, work on statins, HIV protease inhibitors, benzodiazepines, calcium channel blockers
27
what inhibit CYP3A4
ritonavir, macrolide antibiotics, grapefruit juice, ketoconazole
28
what induce CYP3A4
rifampicin, anticonvulsants, St. John's wort
29
what happen to drug if the CYP3A4 inihibited
decrease drug clearance, so T1/2 in the body and the maximal serum conc. are increased which lead to toxicity
30
what is clinical significan of CYP3A4 induction?
1, increased clearance of drugs metabolised by CYP3A4 2, diminished theraputic effects 3, decreased systematic exposure
31
what is CYP2D6?
a debrisoquine hydroxylase
32
what are the drug that CYP2D6 act on ?
codeine, tamoxifen, antiarrhythemics, tricyclic antidepressants, selective serotonin-reuptake inhibitors (SSRIs), many antipsychotic drugs and beta adrenoceptor antagonists
33
which country shows the highest ultrarapid metaboliser for CYP2D6?
Ethiopians is the highest, chinese is the lowest
34
what country have the highest intermediate metaboliser for CYP2D6?
chinese have the highest, caucasian is the lowest
35
what are the major phase II enzymes
N-acetyltransferases, UDP-glucuronosyltransferases, Sulfotransferases and glutathione S-transferases
36
what functional group (4) does glucuronidation act on | and what is the name of this enzyme
1. -OH 2. -COOH 3. -NH2 4. -SH UGTs (UDP-Glucuronosyltransferases)
37
what kind of chemical reaction is glucuronidation?
nucleophillic substitution rxn
38
what functional group (3) is sulfation act on
- NH2 - SO2NH2 - OH
39
what enzyme does sulfation and cofactor does this enzyme require
SULTs (sulfotransferases) | cofactor is PAPS
40
what functional groups (3) undergo actylation
1. - NH2 2. - SO2NH2 3. -OH
41
what enzyme does acetylation
NATs (N-acetyltransferases)
42
which country have the highest incidence on NAT 2 variants for defective alleles
mediterranean, caucasian and sub-saharan populations
43
is type A adverse drug rxns depends on dose?
yes.
44
can you predict type B ADR from known pharmacology
not usually
45
which type of ADR is dependent on genetic factors
type A. | type B is dependent on usyally uncharacterised host factors.
46
which type of ADR is more frequent
type A with wild severity
47
which type of ADR causing more clinical burden
type B with high morbidity and high mortality. Tpe A have high morbidity but low mortality
48
during phase I-III, what ADR can be seen
type A
49
when is type B ADR happen,during which phase
phase IV, occasionally phase III
50
can be use animal model for typeB ADR
no. No known animal models. only Type A is reproducible in animal models.
51
what are the main category for genetic polymorphisms
pharmacokinetics and pharmacodynamics
52
what is pharmacokinetics?
involve in drug metabolism such as absorption, distribution, metabolism and excretion
53
what is pharmacodynamics
involve in drug target e.g. receptors, ion channels, enzymes and immune system
54
what is the percentage that the caucasian carry 2 null allleles for CYP2D6
6%
55
what is the most common variants CYP2D6?
CYP2D6*4 and CYP2D6*5 coding for non-functional products
56
absent or reduced CYP 2D6activity can lead to ADRs by the follow mechanisms (3)
1. decrease 1st pass metabolism and drug elimination 2. accumulation of the drug as a result of reduced metabolism 3, re-routing of metabolism
57
which drug is metabolised by CYP2D6 is withdrawed? why?
perhexilene, it is associate with a higher risk of hepatotoxicity and neuropathy in CYP2D6 poor metabolisers.
58
what drug treated with CYP2D6 poor metaboliser causing a higher risk of ADR? what effect does it have?
with pstchotropic agents. | it will have a prolonged hospital stay and higher treatment costs
59
what metabolise S-enantiomer of warfarin, which is responsible for anticoagulant
CYP2C9
60
what are the form of variant for CYP 2C9
CYP2C9 *2 where cysteine substitutes for arginine at position 144 CYP2C9 *3 where leucine substitutes for isoleucine at residue 359 in the substrate binding site
61
what is the effect of variant in CYP2C9
decreased clearance of warfarin by the allelic variants
62
why not do genotype for the CYP2C9
1. R-warfarin is also metabolised by CYP3A4 AND CYP1A2 2. pharmacodynamic factors also involve in e.g. Vitamin K status and thyroid disease (alter the sensitivity to anticoagulant) 3. there are mutations in clotting factors that might alter sensitivity to warfarin 4. there are other methods of dose titration and dose maintenance with warfarin 5. genotype required within 24 hours of administrations
63
what is TPMT ( thiopurine methyltransferases)
involved in the metabolism of 6-mercaptopurine (6-ML) and its pro-drug azathioprine, TPMT activity reduce the formation of thioguanine nucleotides(cytotoxicity)
64
what is the relationship b/t cellular accumulation of thioguanines and TPMT activity
inversely related
65
what are the most common form of TPMT variant (3)
TPMT *2, TPMT *3A and TPMT *3C
66
how much percentage of caucasians exhibit intermediate activity?
at leat 10%
67
what happen to patients with deficient TPMT with full dose of 6-MP
lead to fatal haemopoietic toxicity
68
in children, what does TPMT deficiency lead to higher risk of?
secondary myelodysplasia leukaemia
69
what is UGT1
do glucuronidation of bilirubin, Gilbert's syndrome shows decrease in activity in UGT1
70
what is the prodrug for SN-38 and reaction convert this?
Irenotecan undergo carboxylesterase to form this | SN-38 have anti-tumour activity
71
what metabolise SN-38
glucuronidation by UGT1A1
72
what increase the risk factor for irinotecan toxicity? | does this associate with coding region polymorphosm
heterozygous or homozygous genotype for UGT1A1*28 in the promoter region. it does not relate to gene coding polymorphorism
73
what is p-glycoprotein (PGp)
an efflux pump with wide substrate specificity
74
what gene encode the Pgp
multi-drug resistance gene (ABCB1)
75
polymorphorism in exon 26 of the ABCB1 gene is functional?
it is functional, but the homozygous for this polymorphism had the lowest Pgp expression ad the highest digoxin plasma conc.
76
G6PD deficiency, what mode of inheritance is it?
sex-linked
77
what does difiency in G6PD cause
haemolysis in the presence of stress
78
what does normal G6PD do?
it reduces NADP while oxidizing glucose-6-phosphate, thus providing a source of reducing power that maintains cellular glutathione in the reduced form.
79
what happen if there is absence of reduce glutathione?
the red cell is susceptible to xoidative damage from drugs---haemolysis , a fall in haemoglobin, fever ans the formation of dark urine
80
what happen when using drug for treating alzheimers
it inhibits the acetylineasterase, in a promotoer polymorphorism, this impairs the transcriptional response..
81
what happen if you have disruption of 2 adjacent HNF3 (hepatocyte nuclear factor 3) binding site?
it cause the acetylcholinesterase to increase, which increase the sensitivity to acetylcholinesterase pyridostigmine
82
what subtitution predipose to the occurence of tardtive dyskinesia following treatment with typical neuroleptic agenets.
a serine to glycine substitution in the gene encoding the dopamine D3 receptor
83
what is tarditive dyskinesia due to?
supersensitivity to dopamine
84
what changes after the serine to glycine substitution in gene encoding for D3 receptor?
this nalter the tertiary structure of the D3 receptor and increased affinity for dopamine
85
what mutation account fot 50% of the malignant hyoerthermia?
mutations in the gene encoding the ryanodine receptor. the mutation make ryanodine receptor more sensitive, result in enhanced rates of Ca released from S.R/ lead to muscle contraction and glycolytic and anaerobic metabolism that is characteristic of malignant hyperthemia.
86
what restrict the use of terfenadine, cisapride, thioridazine and sertindole ?
the prolonged QT-interval in ECG and occasianal torsades de points (TdP). this is due to mutations in various ion channel that are responsible for normal ventricular repolarisation
87
how did the drug cause prolonged QT interval
by blocking the rapid delayed rectifier K current
88
if we induce TdP, what mutation can be caused?
missense mutation in KCNE2, this alter the K channel such that the affected subunit MinK-related peptide 1 acitivated less readily at baseline and was 3 fold more sensitive to drug inhibition
89
KCNE2 SNP associate with?
prolonged QT-interval follow the administration of sulfamethoxazole-trimethoprim, probably by accerlerate the deactivation of the channel.
90
analysis of gene encoding enzymes that are responsobile for drug bioinactivation including microsomal epoxide hydrolase, glutathionine transferases, catechol-O-methyltransferase and quinone reductase failed to reveal an association with CBZ hypersensitivity
true

U5A4 pharmacology quiz (1 decks)

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