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DIsease and Defense > Pharmacology > Flashcards

Pharmacology Flashcards

1
Q

4 factors that affect a drug’s ability to cross biological membranes

A

1) Molecular size (Can be affected by plasma protein binding)
2) Lipid solubility- estimated by oil:water partition coefficient
3) Degree of ionization - affected by tissue pH, affects lipid solubility
4) Concentration Gradient - created at site of administration

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2
Q

Bioequivalence

A

(a) rate of generic and brand name must be similar - estimated by Cmax and bioavailability
(b) Drugs are considered bioequivalent if the 90% CI of mean AUC and mean Cmax of generic product is within 80-125% of the brand product.

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3
Q

Bioavailability (F)

A

Fraction of unchanged drug reaching the systemic circulation following administration by any route
AUC (route)/AUC (iv)

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4
Q

First-pass effect

A

Drug metabolism of po drugs that occurs in liver before drug enters systemic circulation

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5
Q

Estimate of rate of absorption

A

Difficult to measure, typically estimated by the peak Cp or teh time needed to attain the Cp

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6
Q

Affect of drug formulation on rate of absorption by oral route

A

Liquid preparations/ rapidly disintegrating tablets –> fast!
enteric coated products or sustained release preparations - slower

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7
Q

General factors affecting drug absorption (5)

A

Solubility in biologic fluids (need some hydrophilicity and some hydrophobicity)
Rate of dissolution of solid for oral dosage formulation or suspended particles (parenteral)
Concentration of drug at site of administration
Circulation at site of absorption
Area of absorbing surface

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8
Q

Acid/base effect on oral absorption

A

weak acids are neutral at lower pH’s (should absorb better in stomach)
weak bases are uncharged at higher pH’s (should absorb better in upper small intestine)
BUT Surface area trumps it!!!

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9
Q

Effect of gastric emptying time on drug absorption

A

increased GI motility increases speed of stomach emptying and hence rapidity of absorption (drugs get to small intestine faster!)
Food delays absorption of most drugs

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10
Q

Is the food guideline to protect the stomach or the drug?

A

Take without food–> protects drug
Take with food–> protect stomach
Enteric coatings can prevent dissolution in stomach

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11
Q

Pros and cons of controlled release preparations

A

Pros - > overnight, decreased frequency of administration (better compliance) , elimination of peaks and troughs
Cons- greater interpatient variability in systemic levels obtained and dosage form failure resulting in “dose dumping”

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12
Q

Rectal admin

A

useful in unconscious, vomiting, post-GI surg, or uncooperative patients
~50% o f dose will bypass liver, so first pass metabolism is less than oral

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13
Q

Sublingual/buccal

A

Fast onset, high bioavailability
Drugs drain directly into superior vena cava, bypassing first pass metabolism
Useful for lipid soluble and potent drugs (small surface are a for admin)

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14
Q

Intravenous

A

Most direct, 100% bioavailability
Good for narrow therapeutic index drugs
bypasses absorption barriers
Most hazardous route

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15
Q

Intramuscular

A

onset and extent of absorption are affected by bloodflow at site of injection
Suspensions have a slower, more sustained absorption
Absorption can be erratic with limited solubility
Pain, tissue necrosis and microbial contamination possible

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16
Q

Subcutaneous

A

generally approaches bioavailability of IV route
Slower, constant rate of absorption
Only for non-irritating crugs

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17
Q

Inhalation

A

Fast rate of onset, Bioavailability of ~100% for systemic

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18
Q

Transdermal

A

Application of patch for systemic conditions, avoids first pass metabolism.
Prolonged drug levels achieved, potential for toxicity
Drug must be potent and able to permeate skin

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19
Q

Inhalation - local vs. systemic

A

For Local admin - aerosolized particles

Systemic- Molecules should be administered

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20
Q

Topical

A

Localized application to skin, minimal systemic absorption

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21
Q

Ion Trapping

A

At equilibrium, UNIONIZED concentration of drug is the SAME on both sides of the
membrane, but TOTAL concentration of drug is greater on side where ionization is
greater - drugs are trapped where they are predominantly ionized
• Acidic drugs are trapped in the more basic solutions
• Basic drugs are trapped in the more acidic solutions

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22
Q

Clinical significance of ion trapping

A
  • alkalization of urine can trap weak acid aspirin in overdose situations
  • greater potential to concentrate basic drugs in acidic breast milk (opioids)
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23
Q

Drug binding proteins in blood

A

Albumin binds acidic drugs

Alpha 1 acid glycoprotein binds basic drugs

24
Q

Example of displacement drug-drug interaction

A

salicylates displace methotrexate (narrow TI cancer drug)

25
Q

Phase I metabolism reactions

A

redox, hydrolysis

26
Q

Activation of opioids

A

Codeine –> Morphine

Hydrocodone –> Hydromorphone

27
Q

Phase II conjugations

A

Glucuronidation
N-Acetylation
Glutathione conjugation
Sulfate conjugation

28
Q

Phenobarbital

A

Inducer; Pharmacokinetic tolerance

29
Q

Phenytoin

A

Inducer

30
Q

Carbamazepine

A

Inducer; pharmacokinetic tolerance

31
Q

Rifampin

A

Inducer

32
Q

Ethanol

A

inducer, induces CYP 2E1 to metabolize acetominophen to a hepatotoxic metabolite

33
Q

St. John’s Wort

A

Inducer

34
Q

Tobacco/ marijuana smoke (not nicotine)

A

Inducer

35
Q

Cimetidine

A

Inhibitor

36
Q

erythromycin/clarithromycin

A

Inhibitor

37
Q

Ketoconazole/ azole antifungals

A

Inhibitor

38
Q

Fluoxetine, other SSRI’s

A

Inhibitor

39
Q

Grapefruit Juice

A

Inhibitor

40
Q

HIV protease inhibitor

A

Inhibitor

41
Q

Omeprazole

A

Inhibitor

42
Q

Cyp 2D6

A

Metabolizes Codeine, genetic variation is important

43
Q

N-Acetyl Transferase

A

Metabolizes Isoniazid (TB drug), genetic variation can lead to peripheral neuropathy

44
Q

Chronic alcohol exposure

A

without liver damage, leads to induction of certain disease states.

45
Q

p-glycoproteins

A

Transport drugs out of the body. In intestines they decrease absorption, and in kidneys they enhance excretion. There’s a potential for consequences of genetic variation

46
Q

Glomerular Filtration

A

120 ml/min drug clearance
Any drug smaller than albumin will be filtered out
Only free drug (NOT protein bound) will be cleared
1-4 hr half life, affected by renal function

47
Q

Active tubular secretion

A

120- 600 ml/min
Stronger acids and bases
Saturable transporters
plasma protein binding does not affect rate

48
Q

Tubular reabsorption

A

Lipid soluble molecules are reabsorbed. A key purpose of metabolism is creating more water soluble metabolites that will not be reabsorbed.

49
Q

Low extraction drug

A

Drug is not significantly metabolized in the liver and hepatic clearance does not contribute to total clearance

50
Q

High extraction drug

A

Drug is significantly metabolized in the liver and hepatic clearance contributes significantly to total clearance

51
Q

Treatments for methanol/ ethylene glycol poisoning

A

Ethanol (competitive inhibition of alcohol dehydrogenase)
fomepizole - direct AD inhibitor
Hemodialysis/gastric lavage
Sodium bicarb to correct acidosis

52
Q

Risk factors for hepatocellular damage by acetaminophen

A

-enhanced CYP2E1 function
-Decreased hepatic glucothione
Both risk factors are more severe in heavy drinkers

53
Q

Acetaminophen poisoning treatment

A

Activated charcoal and gastric lavage

N-Acetylcysteine (provides precursor for glucothione synthesis (IV or oral)

54
Q

When to use hemodialysis

A

1) Toxin has small Vd

2) Toxin does not have any significant protein binding capacity

55
Q

Hemoperfusion

A

Useful for high molecular weight drugs with poor water solubility

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