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PHAL211 > Pharmacokenetics > Flashcards

Pharmacokenetics Flashcards

1
Q

Therapeutic window

A

between MEC (Min Effect Conc) and MTC (Min Tox Conc)

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2
Q

Absorption

A

The process of the drug entering the bloodstream

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3
Q

Distribution (and factors)

A

Dispersion of drug throughout tissues in the body (permeability, blood perfusion, plasma protein binding)

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4
Q

Metabolism

A

The conversion of a drug into other molecules to increase excretion

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5
Q

Excretion

A

removal of drug in body (faeces, urine, sweat, saliva, exhalation) gall bladder (MW > 350), lungs (inhaled + non soluble)

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6
Q

Bioavailability (and factors)

A

F=AUCoral/AUCiv - fraction of drug dose ingested orally that goes to the systematic circulation (enzyme activity, pH, gastric motility)

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7
Q

Vd

A

= A/Cp - volume drug appears to be uniformly distributed at the concentration measured in the plasma.

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8
Q

Css

A

steady state conc - equilibrium (in=out/dose=elimination)

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9
Q

Loading dose

A

target Css x Vd

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10
Q

Topical

A

surface

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11
Q

enteral (2)

A

GI tract (oral, sublingual-dissolved)

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12
Q

parenteral (3)

A

avoid GI (IV bolus - all at once/infusion, IM-intramuscular, subcutanous-underskin)

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13
Q

Oral absorption factors

A

GI motility, disorders, other drugs, illness, blood flow, food, size, ionisation, lipid solubility

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14
Q

Phase 1 metabolism

A

increases water solubility - small changes (oxidation) via CYP450 = target for phase 2

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15
Q

Phase 2 metabolism

A

increases size via conjugation (nutrition/cofactors - niacin NADPH CYP, cysteine GSH, sulphate PAPS)

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16
Q

CYP450

A

mono-oxygenases, NADPH-CYP450 molecule, reactive Oxygen

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17
Q

CYP3A4

A

largest and most common

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18
Q

CYP2D6

A

human polymorphisms = different reactions

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19
Q

CYP2E1

A

smallest

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20
Q

Half life

A

how long it takes to halve conc (exp)

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21
Q

Drug response factors

A

age, ethnicity, pharmacogenetics, enterohepatic circulation, nutrition, intestinal flora, sex, liver and heart disease

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22
Q

Phase two metabolism enzymes

A

Epoxide hydrolase (EH), Sulfotransferase (ST), UDP Glucoronsyl Transferase (UDPGT), Glutathione S-Transferase (GST)

23
Q

Epoxide hydrolase

A

epoxide plus H2O to diol (highly reactive)

24
Q

Sulfotransferase

A

sulphation = phenols (low capacity), alcohols, hydroxyamines, cytosolic (liver, gut, kidneys), cofactor-PAPS

25
Q

UDP Glucoronsyl Transferase

A

glucuronidation = conjugation with endogenous glucuronic acid (UDPGA), liver-sER lumen, attacks diff groups

26
Q

Glutathione S-Transferase

A

glutathione conjugation = endogenous tripeptide, electrophilic centre, soluble or microsomal, GSH, varies

27
Q

B-glucuronidase

A

bacteria? hydrolyses glucuronide conjugated drugs - unconjugated = entero-hepatic recycling (bile duct)

28
Q

Ion trapping

A

alter urine pH to change excretion, pH = pKa +Log(ionised/unionised), pH below pKa = unionised = reabsorbed

29
Q

Metabolic elimination

A

= 1 - fu (fraction unchanged)

30
Q

Clearance

A

Cl (L/h) plasma drug conc at steady state (constant, low = high Css)

31
Q

Rate of elimination

A

Cl x Cp (mg/h)

32
Q

Partition coefficient

A

p = [L]/[W] soluable, high p = more absorption

33
Q

Rule of 5

A

M < 500 daltons, octanol-water partition coefficient log P < 5, <5 H bond donors, <10 H bond acceptors

34
Q

BBB

A

passive transport, size dependant gaps and transporter protein families (efflux proteins eg PGP1) , 98% don’t cross (M<400, < 8-10 H bonds)

35
Q

Penicillin in bioavailability

A

unstable in the gut = excreted unchanged

36
Q

Tubocurarine in bioavailability

A

poorly absorbed as it is not lipid soluble

37
Q

Simvastatin in bioavailability

A

metabolised in gut wall

38
Q

Glyceryl trinitrate GTN in bioavailability

A

metabolised in intestine/liver = 100% first pass

39
Q

Morphine in bioavailability

A

50-70% first pass metabolism (some oral bioavailability)

40
Q

Benzodiazepine in metabolism

A

action effected by hormones, elderly decreases in metabolism

41
Q

Prodrug for active metabolite

42
Q

Drug inactivation example

A

Alcohol to acetaldehyde to (disulfiram inhibits ALDH) acetic acid

43
Q

Toxic metabolite

A

Paracetamol can go to four substrates one causes liver cell death (NAPQI)

44
Q

CYP grapefruit inhibits transcription and dextamethasome promotes transcription (cocaine is substrate)

45
Q

CYP2D6 substrates

A

CYP fluoxetine inhibits, antidepressants and codeine are substrates

46
Q

CYP ethanol induces via ligand stabilisation, paracetamol is substrate.

47
Q

Phase 2 metabolism drugs

A
  • Epoxide hydrolase = tobacco smoke (PAH to diol, carcinogenic)
  • UDP Glucoronsyl Transferase = THC-COOH (CYP2C)
48
Q

Paracetamol metabolites

A

UDPGT, ST, CYP2E1 -> GST, NAPQI (cell death)

49
Q

Codeine metabolism

A

glucuronides excreted, heroin and codeine -> morphine -> glucuronidine = bad

50
Q

Ethanol elimination

A

zero order elimination (saturable)

51
Q

BBB diffusion example

A

Crizotinib- bad BBB, lorlatinib - good BBB diffusion

52
Q

Renal excretion

A

A: Glomerular filtration of plasma water + unbound drugs
B/C: Active tubular secretion (carrier meditated)
D: Tubular reabsorption of nutrients in renal tubule
E: Urinary excretion

53
Q

Absorption barriers

A

Lipid membranes, transporter proteins, enzymes

PHAL211 (5 decks)

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