Drug Interactions

Question 0

Inhibitor

Answer 0

compounds that inhibit the activity of the enzyme resulting in less drug metabolism and therefore serum job levels will increase

Example: amiodarone inhibits the metabolism of warfarin and therefore the INR increases

Question 1

Inducer

Answer 1

Compounds that either increase the production of an enzyme or increase the activity of the enzyme

Results in lower blood levels of the substrate

My fave been induces the metabolism of drugs at various Cyp sites

Question 2

Prodrugs

Answer 2

Prodrugs work opposite of other drugs when it comes to an induction and inhibition

Inducers cause more of the drug to be converted to the active form and inhibitors prevent the conversion to the active drug

Example: codeine to morphine

Question 3

P-glycoprotein

Answer 3

Pumps drugs back into the gut to exit out of the body

This process can also be inhibited or induced

Question 4

Strong inhibitors of P-glycoprotein

Answer 4

Itraconazole, ketoconazole, verapamil, antivirals, clarithromycin, erythromycin, amiodarone, Quinidine

Question 5

Strong inducers of P-glycoprotein

Answer 5

Rifampin, carbamazepine, phenytoin, St. John’s wort, Ritomavir

Question 6

Substrates of P-glycoprotein

Answer 6

Aliskiren, , colchicine, dabigatran, cyclosporine, digoxin, fexofenadine, posaconazole, ranolazime, rivaroxaban, saxagliptan, tacrolimus

Question 7

Cyp inducers

Answer 7

Phenytoin, smoking, phenobarbital, oxcarbazepine, rifampin, carbamazepine, St. John’s wort

Question 8

Strong inhibitors of Cyp

Answer 8

Grapefruit, protease inhibitors, azole antifungal’s, cyclosporine, cimetidine, macrolides, amiodarone, non dihydropyridine calcium channel blockers

Question 9

Amiodarone

Answer 9

Decrease the doses of digoxin warfarin quinidine and procainamide by 30 to 50% when starting Amiodarone

Use lower doses of simvastatin, lovastatin, and atorvastatin

Question 10

Digoxin

Answer 10

Levels increase due to decline in renal function or hypokalemia

Be careful when used with other drugs that lower heart rate such as beta blockers, verapamil, diltiazem, Amiodarone, clonidine, opioids

Question 11

Grapefruit juice

Answer 11

Avoid with simvastatin, lovastatin, atorvastatin, and calcium channel blockers as it will cause an increase in the drug concentration

Grapefruit causes the drug metabolizing enzymes to be inactive

Question 12

Lamotrigine and valproate

Answer 12

Combination has high risk for severe rash and requires a careful titration

Question 13

Monoamine oxidase inhibitors

Answer 13

Interactions can cause serotonin syndrome, hypertensive crisis, and potentially are fatal

Monoamines that would have reduced metabolism are dopamine, epinephrine, norepinephrine, and serotonin

Do not use MAOI with SSRIs, SNRIs, TCAs tramadol, levodopa, mitazapine, bupropion buspirone, linezolid, lithium, meperidine dextromethorphan, cyclobenzaprine, triptans

Question 14

Nonselective MAOIs

Answer 14

Should not be used with tyramine rich foods

Examples are aged cheese, air dried meats, wine, beer, anything aged, fermented, pickled or smoked

Question 15

Combination of hydrocodone and tramadol

Answer 15

Both are metabolized by two D6 in patients with out this enzyme or those on 2D6 inhibitors would be an increased risk of respiratory depression

2D6 and inhibitors include fluoxetine paroxetine

Question 16

Codeine

Answer 16

Pts with a lot of 2D6 could receive too much morphine and so could the an infant through breast milk

Conversely those with little 2D6 will have little analgesic effect

Question 17

Oxycodone and methadone

Answer 17

Metabolized by 3A4 and should not be used with 3A4 inhibitors as it can be fatal

Question 18

PDE5 Inhibitors

Answer 18

Contraindicated with nitrates

Question 19

Chelation risk with quinolones and tetracyclines

Answer 19

Antacids, sucralfate,bile acid resins, magnesium, aluminum, calcium, iron, zinc, and multivitamins should be separated from these drugs

Question 20

Statins

Answer 20

3A4 statins: atorvastatin, simvastatin, lovastatin

Drugs that inhibit 3A4 will increase risk of muscle breakdown and pain which could lead to kidney injury

Question 21

Calcineurin inhibitors (tacrolimus and cyclosporine)

Answer 21

Immunosuppressants

Inhibitors of Cyp (Azoles, macrolides, SSRIs,

INDUCER: rifampin

DO NOT TAKE WITH GRAPEFRUIT JUICE

Question 22

Bleeding risk due to additive interaction

Answer 22

Anticoagulants (warfarin, dabigatran, rivaroxaban, heparin)
Anti platelets (aspirin, dipyridamole, clopidogrel, prasugrel, and ticagrelor)
Others: NSAIDs, SSRIs, SNRIs, ginkgo, fish oil, primrose, vit E, garlic, glucosamine ( most of the natural products inc bleeding risk without inc INR

Question 23

Hyperkalemia due to additive effect

Answer 23

Main drugs that effect potassium: spironolactone and eplerenone

Contra to use: k>5 mEq/ml, avoid use with NSAIDs

Additive effects from ACEi, ARBs, Aliskiren, amiloride, triamterene, drospirenone OC

Question 24

CNS depression

Answer 24

alcohol, most pain medications, skeletal muscle relaxants, anticonvulsants, benzos, barbs, hypnotics, mirtazapine, trazodone, propranolol, clonidine, many illicit substances

Question 25

QTc prolongation

Answer 25

Antiarrythmics, FQs, AG, ziprasidone, citalopram, escitalopram and others can be additive

Question 26

Ototoxicity

Answer 26

Salicylates, vancomycin, AG, cisplatin, loops