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Pharmacology > Week 12 Pharm > Flashcards

Week 12 Pharm Flashcards

1
Q

routes of drug administration and conditions for use

A

enteral = GI: oral, sublingual, rectal
-most common, easy, cheap, must survive 1st pass metabolism
parenteral: subcutaneous, IV, intramusc.
-IV: need fast or can’t do GI, can be unconscious, stable
other: inhalational, topical, transdermal
general considerations:
-drug: size, solubility, pH/pKa,
-patient: condition, age, compliance
-therapy goals: urgency, location, effect

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2
Q

factors that influence drug absorption and availability

A
  • pKa and pH -> charge, solubility (best absorbed in unionized HA or B form); size; solubility
  • bioavailability = fraction absorbed. F=(in circulation)/(dose given)
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3
Q

Vd

A

volume of distribution: the theoretical compartment the drug is dissolved in
-large Vd= mostly in tissues, small Vd=more in blood/ECF

recall: body 60% H2O (42L), 2/3 ICF, 1/3 ECF–> 2/3 interstitial, 1/3 plasma

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4
Q

factors that influence drug distribution in blood

A
  • protein binding: less free drug in blood
  • perfusion: brain, heart, liver, kidneys first
  • conc gradient, pKa/pH, liposolubility
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5
Q

mechanisms of drug metabolism

A

usu in liver: goal= make more excretable
Phase I: Redox/hydrolysis
-CYP450: add/uncover polar groups
Phase II: conjugation
-non P450 enzymes, covalent add’n of large polar molecules
-urine excretion: must make more polar/charged

some drugs metabolized extensively by gut bacteria

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6
Q

drug excretion

A
  • may occur unchanged, or after phase I or phase II
    kidney: passive (small), tubular secretion (large, protein complexes), tubular reabsorption ( uncharged drug follows conc gradient back to blood) t limit). subject to enterohepatic recirculation
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7
Q

enterohepatic circulation

A
  • gut bacteria hydrolyze phase II conjugates -> no longer polar -> reabsorbed
  • antibiotic use can effect
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8
Q

AUC

A

area under the curve, measure of F (fraction absorbed)

  • useful for comparing administration routes
  • bioavailability= AUC oral/ AUC injected x 100%
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9
Q

CYP450 inducers

A 
alcohol (esp chronic)
cigarettes
Rifampin
Phenytoin, carbamazepin (epilepsy drugs)
St John's wort
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10
Q

CYP450 inhibitors

A

grapefruit juice
fluconazole, ketoconazole (-azole antifungals)
fluoxetrine (antidepressant)
erythromycin (macrolide antibiotics)

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11
Q

therapeutic range

A

range between MEC (min effective conc) and MTC (toxic),

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12
Q

Css

A

5 half lives=time taken to reach
rate of infusion = rate of clearance
peak and trough levels fluctuate around
can give loading dose to reach faster, follow with smaller MD

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13
Q

time required for drug washout

A

5 half lives

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14
Q

first vs zero order kinetics

A

first order = normal, constant fraction of drug eliminated per unit time (%), does not depend on dose.

zero order = elimination process saturated, constant amount of drug (mg/mL) per unit time (linear) depends on dose. more danger of OD

ex. alcohol, high dose aspirin, phenytoin,
* some 1st order drugs show during high/OD

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15
Q

factors contributing to variability in drug response between patients

A
  • compliance
  • drug interactions
  • disease (ADME)
  • gender, ethnicity: metabolism differences?
  • AGE
  • start low and go slow
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16
Q

pediatric differences for drug absorption

A
  • higher gastric pH: affects abosorption of weak acids/bases, more acid labile drug
  • stratum corneum thinner: percutaneous absorbed more
17
Q

geriatric differences for absorption

A
  • higher gastic pH: more acid labile drugs, changed absorption of week acid/base drugs
  • faster GI emptying and less blood flow = decreased absorption
18
Q

geriatric differences for distribution

A
  • more adipose tissue: lipophilic drugs lower in plasma
  • less TBW: hydrophilic drugs have higher conc
  • less serum albumin = more free drug
19
Q

geriatric differences in metabolism and excretion

A
  • decreased liver mass and hepatic blood flow, decreased phase I enzyme activity -> longer half life
  • phase II rxns generally unchanged
  • decreased renal function (size, functioning nephrons, blood flow)
20
Q

paediatric differences in drug distribution

A
  • larger % body water: may larger mg/kg dose of hydrophilic drugs
  • less protein binding in plasma = more free drug
21
Q

paediatric differences for drug metabolism and excretion

A
  • decreased hepatic metabolism (Phase I enzymes immature)

- decreased renal function (especially pre term)

22
Q

Factors to consider when assessing the impact of drug interactions

A
  1. toxicity profile: margin of safely width and nature or toxicity
  2. Regimin: dose, frequency, duration
  3. extent of interaction: weak/strong, exclusive to one enzyme?, genetic factors
  4. frequency of interaction in population: genetics, patient factors
23
Q

Pharmacokinetic drug interactions: absorption

A
  • chelation: binds to free ions, can reduce plasma levels
  • binding: directly bind another drug
  • indirectly reduce absorption: gastric pH, GI motility,
  • P-glycoprotien: (pump drug out, BBB and GI) induced or inhibited
24
Q

Pharmacokinetic drug interactions: distribution

A

-displacement of protein binding very rarely has clinically significant effects, must be combined with decreased metabolism etc

25
Q

Pharmacokinetic drug interactions: metabolism

A

Phase I
-CYP450 inhibitors (competitive or allosteric) and inducers
-3A4>2D6>2C>1A2
Phase II: similar principles, but much less important
enterohepatic circulation: antibiotic reduces by killing bacteria

26
Q

Pharmacokinetic drug interactions: excretion

A

filtration: binding may reduce, minor role
secretion: inhibition (may be beneficial!)
reabsorption: enhance or reduce (esp ions or drugs that resemble Na+)
urine pH: affects reabsorption

27
Q

pharmacodynamic interaction

A

additive/synergistic

antagonistic

28
Q

cyp effects: fluoxetrine

A

inhibits CYP450

antidepressant

29
Q

cyp effects: rifampin

A

induces CYP450

30
Q

cyp effects: erythromycin/azithromycin

A

inhibits CYP450

31
Q

cyp effects: ketoconazole

A

inhibits CYP450

32
Q

cyp effects: carbamazepin

A

induces CYP450

epilepsy drug

33
Q

cyp effects: phenytoin

A

induces CYP450

epilepsy drug

34
Q

cyp effects: fluconazole

A

inhibits CYP450

35
Q

cyp effects: St. John’s Wort

A

induces CYP450

36
Q

cyp effects: grapefruit juice

A

inhibits CYP450

37
Q

cyp effects: chronic ethanol use

A

induces CYP450

38
Q

cyp effects: cigarette smoking

A

induces CYP450

Pharmacology (6 decks)

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