WCVD Papich lectures

Question 1

Fluoroquinolones should not be mixed with what compounds because they can chelate the drug and inhibit absorption?

Answer 1

metals - particularly iron, magnesium, aluminum; and calcium

Question 2

Decreasing the stomach acidity inhibits oral absorption of what drugs as they are better absorbed in an acidic environment?

Answer 2

antifungal azoles (ketoconazole, itraconazole), pimobendan, oclacitinib

Question 3

Decreasing the stomach acidity enhances absorption of what drugs because they are less stable in an acidic medium?

Answer 3

penicillins, omeprazole

Question 4

Sucralfate contains what ingedient that can interfere with absorption of fluoroquinolones?

Answer 4

aluminum

Question 5

What ingredients in antacid drugs can bind to tetracyclines and prevent absorption from the GI tract?

Answer 5

magnesium and calcium

Question 6

Where are multi-drug resistance efflux pump (P-glycoprotein pump) located?

Answer 6

intestine, biliary tract, liver, kidney tubules, placenta, blood-brain barrier

Question 7

What drugs inhibit the P-glycoprotein pump?

Answer 7

fluoxetine, paroxetine, itraconazole, ketoconazole, methadone, verapamil, quinidine, bromocriptine, tamoxifen, St. John’s Wort, erythromycin, pentazocine, carvedilol, cyclosporine, chlorpromazine, Grapefruit juice

Question 8

Ketoconazole can cause drug interactions through its activity on what pathways?

Answer 8

inhibits P-glycoprotein AND cytochrome p450

Question 9

Drugs that are substrates for P-glycoprotein

Answer 9

Doxorubicin, Vincristine, Vinblastine, Aldosterone, Cortisol, Dexamethasone, Methylprednisolone, Erythromycin, Cyclosporine, Ketoconazole, Itraconazole, Terfenadine, Phenothiazines, Tetracycline, Doxycycline, Levofloxacin, Loperamide, Morphine, Digoxin, Dilitiazem, Verapamil, Tacrolimus, Ivermectin, Amitriptyline, Ondansetron

Question 10

What drugs increas the activity of P-glycoprotein? What effect does this have on other drugs?

Answer 10

rifampin, corticosteroids, phenobarbital – results in increased clearance of other drugs

Question 11

What substances are cytochrome enzyme inducers?

Answer 11

phenobarbital, phenytoin, phenylbutazone, pentobarbital, diazepam, alcohol, chlorinated hydrocarbons, griseofulvin, estrogen, progestogens, diphenhydramine, rifampin, hyperthyroidism

Question 12

What is a phase I reaction in the liver?

Answer 12

metabolize drugs to a more water-soluble compound - often oxidative reactions, but other reactions (reduction) can occur

Question 13

What are phase II reactions in the liver?

Answer 13

conjugation reactions – e.g. conjugation with glucuronic acid; other conjugation reactions with amino acids, acetyl groups, and sulfate also are possible

Question 14

Name inhibitors of cytochrome p450 enzymes

Answer 14

cimetidine, ketoconazole, organophosphates, quinidine, cyclophosphamide, ondansetron, cyclosporine, diazepam, loperamide, morphine, chloramphenicol, erythromycin, interferon, tetracycline, verapamil, propofol, vincristine, fluoxetine, ivermectin

Question 15

Which drugs are most likely to cause a problem due to their role as a cytochrome p450 inhibitor?

Answer 15

ketoconazole, cyclosporine, chloramphenicol

Question 16

Which drugs are most likely to cause a problem due to their role as a cytochrome p450 inducer?

Answer 16

rifampin, phenobarbital

Question 17

T/F: Antibiotics administered to dogs and cats cause resistance in bacteria.

Answer 17

False - antibiotic exposure can SELECT for resistant bacteria

Question 18

What are the most common bacteria producing resistant infections in small animals?

Answer 18

E. coli, Pseudomonas aeruginosa, Methicillin-resistant Staph spp., Enterococcus spp.

Question 19

T/F: Administration of antibiotics can increase the shedding of drug-resistant fecal bacteria.

Answer 19

TRUE

Question 20

T/F: Use of fluoroquinolones and cephalosporins has been linked to emergence of resistance in staphylococci in dogs.

Answer 20

False - use of specific drugs have not been associated with methicillin resistance but administration of ANY antimicrobial within 30 days of prior to infection was identified as a risk factor

Question 21

Rifampin: Bacteriostatic or bactericidal?

Answer 21

bactericidal

Question 22

Rifampin: MOA?

Answer 22

inhibits bacterial RNA polymerase

Question 23

What is most common adverse effect of rifampin?

Answer 23

hepatoxicity

Question 24

Adverse effects from doxycycline?

Answer 24

renal injury, intestinal disturbances, hepatic injury

Question 25

T/F: All tetracyclines cause dental enamel discoloration.

Answer 25

False - doxycycline does NOT chelate with calcium

Question 26

T/F: Aminoglycosides are equally effective against both gram-positive and gram-negative bacteria.

Answer 26

False - more effective against gram NEGATIVE bacteria

Question 27

Vancomycin: Bacteriostatic or Bactericidal?

Answer 27

bactericidal

Question 28

Vancomycin: MOA?

Answer 28

inhibits cell wall formation

Question 29

Vancomycin: Adverse effects?

Answer 29

skin flushing, pruritus, tachycardia (related to histamine release); nephrotoxicity, ototoxicity

Question 30

Linezolid: route of administration?

Answer 30

oral and IV - oral absorption is ~100%

Question 31

What enzyme does linezolid inhibit?

Answer 31

mild, reversible inhibitor of monoamine oxidases A and B

Question 32

Carbapenems: Bacteriostatic or bactericidal?

Answer 32

bactericidal

Question 33

Disadvantages of imipenem?

Answer 33

inconvenience of administration, short shelf-life after reconstitution, high cost

Question 34

T/F: Penicillins have little activity on gram negative bacteria.

Answer 34

True - even when combined with beta-lactamase inhibitors

Question 35

Unique adverse effect of prednisolone in cats?

Answer 35

congestive heart failure

Question 36

Why is acetaminophen more toxic to cats than dogs?

Answer 36

cats are deficient in glucuronidation enzyme (required for elimination of acetaminophen)

Question 37

Unique adverse effect of voriconazole in cats?

Answer 37

neurologic/ocular problems

Question 38

Why are slow-release tablets not well absorbed in cats?

Answer 38

shorter intestines - GI transit time variable

Question 39

What drugs have a slower clearance in cats due to their glucuronidation deficiency?

Answer 39

aspirin, benzoic acid, acetaminophen, chloramphenicol, morphine, desmethyl tramadol (active metabolite of tramadol)