principles of drug rxns

Question 1

asthma drugs

Answer 1

-albuterol, budesonide, salmeterol, ipratropium, montelukast, omalizumab

Question 2

pharmaceutical interactions

Answer 2

chemical interaction b/w 2 drugs - forms precipitate

-ex. penicillin (+) and aminoglycosides (-) –> mixing forms precipitate

Question 3

additive effects

Answer 3

2 equal drugs administered –> twice the effect

-ex. propanolol and cardiac depressants

Question 4

synergistic effects

Answer 4

2 drugs used together have greater effects than additive

-ex. nitroglycerin and PDE inhibitors (sildenafil) –> hypotension

Question 5

antagonistic effects

Answer 5

2 drugs with different mechanisms and receptors but having adverse EFFECTS
-ex. Epi and histamine –> bronchial constriction/relaxation

Question 6

altered drug absorption

Answer 6

• altered pH –> ion trapping (more absorption with uncharged - blocked by H2 blockers ex. cimetidine, ranitidine)
• bacterial flora –> higher levels of digoxin w/ antibiotics increasing toxicity
• chelation –> prevents absorption (ex. cholestyramine binding digoxin)
• active transport competing –> less absorption or excretion
• mucosal damage –> more absorption due to thinner mucosa (antineoplastic drugs –> more digoxin absorption)
• gut motility –> increase absorption with slower motility (atropine, metaclopramide increase cyclosporine absorption, opioids, laxatives)

Question 7

altered drug distribution

Answer 7

stay in central compartment when bound to albumin or other proteins –> prevent drug-receptor interaction

• bucolome –> displaces warfarin increasing anti-coagulation
• PDE –> displace testosterone

Question 8

altered biotransformation

Answer 8

• alter hepatic blood flow –> change metabolism
• CYP enzyme inducers
• CYP enzyme inhibitors
• less drug available with more metabolism

Question 9

CYP enzyme inducers

Answer 9

• barbiturates, carbamazepine, rifampin –> induce CYP1A2 and CYP2C9
• both metabolize warfarin
• CYP1A2 metabolizes theophylline
• CYP2C9 metabolizes phenytoin

Question 10

CYP enzyme inhibitors

Answer 10

cemetidine inhibits CYP1A2 and CYP2C9 –> prevent metabolism of benzodiazepines, warfarin, theophylline, phenytoin

Question 11

altered excretion

Answer 11

• less bile –> less drug bound and absorbed
• alter urine pH (ion trap) –> alter excretion rate (stomach, renal)
• renal damage –> less excretion
• inhibit tubular secretion –> more remains in plasma (increase penicillin levels with probenecid)

Question 12

St. John’s wort

Answer 12

anti-depressant activity and wound healing

• influence metabolism of many drugs taken
• ingredients: naphthodianthrones, flavenoids, hyperforin
• induce CYP enzymes & MDR-1 transporters

Question 13

ginkgo biloba

Answer 13

-antioxidant - used in vascular problems, memory loss, dementia, and macular degeneration

Question 14

recreational drugs

Answer 14

many metabolized by CYP3A4

-can be inducers or inhibitors

Question 15

beneficial drug interactions - ketoconazole

Answer 15

immunosuppressant for transplantation

-inhibits CYP3A4 preventing metabolism of cyclosporine (dose sparing)

Question 16

beneficial drug interactions - ritonavir

Answer 16

protease inhibitor and antiviral activity (HIV)
-inhibits CYP3A4 –> increases plasma [] of protease inhibitors by preventing 1st pass metabolism (more drug around to fight off virus)

Question 17

grapefruit juice

Answer 17

affects metabolism of many drugs

-Naringin and Furancoumarin –> inhibit CYP3A4