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CPT > PK/PD > Flashcards

PK/PD Flashcards

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1
Q

PK diagram

A

Check diagram on notes

  • population and individual tailoring
  • predicting toxicity: review all medications
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2
Q

PK requirements- factors for approval

A 
Bioavailabity
T1/2 
Drug elimination
Inter-subject availability
Drug-stud reactions
Safe dose->plasma conc-> right tissue
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3
Q

Pk requirements- factors to consider

A 
New drug repurposed?
Alcohol/smoke
Age/sex/diet
Infection/preg etc
Liver/CVD function
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4
Q

Bioavailabity- definition

Check graph

A

Measure of drug absorption where it can be used
Vd= AUC oral/AUC IV *100%
Drug-> systemic circ vs IV route
Drug admin IV= 100% Vd
Other routes= fraction of IV (1> eg oral)

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5
Q

Vd affected by

A 
Absorption:
Formulation
age(luminal changes) 
food (chelation and gastric emptying)
vomit/malabsorption (Crohn’s)

1st pass metabolism- metab b4 reaching systemic circ= gut lumen/wall/liver

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6
Q

Rate of absorption

A

Dictate visibility of distribution and elimination phase

Fast abs- see D/E phase, slow =D phase masked= see diagram

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7
Q

Modified release preparation

A

Change PK parameters- change coating/tweaking drug- less/more freq dosing
Modified release form of metformin
- take less often, Better adherence
-abs slower: plasma conc shift towards rate of abs
Expensive

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8
Q

Distribution

A

Adequate plasma levels and reach target organ

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9
Q

Factors affecting therapeutic agents

A

Blood flow and capillary structure:
Simple diffusion
Junctions
Active transport

Lipophilicity/hydrophylicity

Protein binding:
Albumin-acidic drug
Globulins-normal
Lipoproteins- basic drug
Glycoproteins- basic drug
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10
Q

Rate of distribution and equilibrate on from IV administration- multiple compartments

A
  1. IV dose admin- 1st compartment
  2. Equilibrate between 2 volumes
  3. distribute and equilibrate between v1 and v2
  4. elimination from v1:Conc in V1 and V2 parallel
    - look at 2 graphs
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11
Q

Drug-protein binding and distribution

A

Free drug: resp/eliminated
Bound: stays in compartment

Clinically important:
Highly protein bound
Narrow therapeutic index
Low Vd

Increased free drug
- 2nd drug displace 1st from binding proteins=bind more efficiently
-increase free drug= resp:
harm potential-preg(change fluidbalance)/renal failiure/ hypoalbunemia(less protein drug can bind to= increase free drug, less response elicited)

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12
Q

Calculations

A

Vd=dose/[drug]plasma

  • Vd in adipose tissue increase as drug sequestered into it
  • Vd decrease as increase [drug]plasma

Conc=amount/vol (mg/L)
-protein binding in plasma= increase free drug in plasma= conc increase

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13
Q

Apparent Vd

A

Smaller- drug confined in plasma and ECF (warfarin)

Larger- drug distributed throughout tissues (Digoxin)

Dose= Vd x [drug]plasma

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14
Q

Metabolism- Phase 1 enzymes cytochrome P450 expose polar regions of drug by:

A

Oxidation
Alkylation
Reduction
Hydrolysis

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15
Q

Metabolism-phase 2 enzymes add a covalent bond, this adds:

A

Glucuronide
Sulphate
Glutathione
N-acetyl

These will: change size and dictate if excreted by kidney/ bile=faeces

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16
Q

Metabolism- last part

A

Phase1/2 products conjugated
Kidney-> urine
Gall bladder -> Bile

17
Q

Structural complexity affects route of metabolism

A

Size
Lipo/hydro philicity/phobicity
Phase 1: convert drugs to lipophilc, metabolites May alter PK/PD

18
Q

Cytochrome p450 (CYPs)

A

Phase 1 catalysed reactions
Genes encode enzymes

  • CYP1A:smoking induced: smoke and take drug can increase/decrease metab of drug stimulate/inhibit it
  • CYP2C:inhibitor
  • CYP20:metab many drugs
  • CYP2E:alcohol metab
  • CYP3A:~50% therapeutics
19
Q

Cytochrome P450 importance:

A

Active drug become inactive MOST

Inactive drug become active
ACEI
Levadopa->dopamine
perindopril->perindoprilat

Active drug become another active structure
Codeine->morphine
Diazepam->oxazepam

20
Q

CYPs induced/inhibited- these things affect phase 1

A

Age
Hepatic disease
Blood flow to hepatic system
Alcohol/smoking

21
Q

CYP2D6

A

Not in 7% Caucasians
Hyperactive/ increase induction: 30% East Africans= increase drug metab
Substrates:BB/SSRI/opioids
Inhibited by some SSRIs/other antiarrythmic/other antidepressants

22
Q

CYP3A4 inhibition

A

grape fruit juice and statin therapy
CYP3A4 metabs lovastatin.
Conc of this in pt high more than not have grape fruit w statin= more muscle fatigue

23
Q

Clinical importance of CYP

A

Drug prescribing
Over the counter drugs
Race/sex/species
Carbamazepine- increase metab of drug (more metab of drug)= mood stabiliser

24
Q

Drug elimination

A

Primary:kidney
Fluids:sweat/tear/saliva
Solids:faeces/hair
Gases:volatile compounds

25
Q

Drug elimination: renal

A

Lower molecular weight polar metabolites
CYP450 exposes the polar region

Affected by:

  • GFR and protein binding: gentamicin, tubular secretion, renal clearance
  • competition for transporters:penicillin
  • lipid sol/pH (chnage ph: increase/decrease drug elimination, reducing:poisoning) flow/ rate:aspirin

Clearance of drug from body: all routes
(Metab and excretion)=mL/min

26
Q

Drug elimination: hepatic

A

High molecular weight with glucoronic acid (pz)

Bile:conjugates
Elimination-faeces/reab

Enterohepatic circ:
Drug-intestine-portal v.-liver
Intestinal lumen:
increase metab/change drugs (may be excreted/reab)
Antibiotic drug interactions-warfarin/morphine

27
Q

Drug elimination; order

Look at 3 graphs

A 
Zero order-
drug elimination specific amount/time
Drug conc 4 time change
Slope= -k
Mass/time

First order:
Change [drug]/t = constant rate, concentration dependent
Increase [drug] body= increase elimination
Steep at first
Exponential equation- learn

Natural log of first order
Slope=-k
T1/2=0.693/k
K=0.693/T1/2

28
Q

T1/2-1st order kinetics

A

Independent of [drug]
Diff for diff drug/PK processes
Elimination T1/2 ranges: min-days/weeks
Reduce [drug] by 50%

29
Q

CL

A

Constant proportion vol blood cleared/t

Rate of elimination from body/drug conc in plasma
mL/min

Increase drug conc increase drug in same vol cleared
Increase elimination rate = amount/Time mg/min
Elimination 4 1/Vd
K=CL/Vd=0.693/T1/2

CPT (3 decks)

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