Drug Interactions

Question 1

name two PGP substrates?

Answer 1

dabigatran (pradaxa)

Rivaroxaban (xarelto)

Question 2

name inhibitors of PGP

Answer 2

cyclosporine
ketokonazole
itraconzole,
LPV/r
IDVr
erythormycin
verapamil
St John's wort

Question 3

Pneumonic for BIG CYP450 inducers

Answer 3

PS PORCS
pheytoin
Smoking
Phenobarbital
Oxcarbazepine
Rifampin
Carbamazepine
St. John's wort

Question 4

Pneumonic for BIG CYP450 inhibitors

Answer 4

G <3 PACMAN
Grapefruit
P rotease inhibotrs
Azole antifungals 
Cimetidine
Macrolides except azithromycin
Amiodarone
Non-dihydropyridines: verapamil/ diltiazem

Question 5

DDIs amiodarone

Answer 5

Avoid w/ agents that prolong the QT
avoid w/ neg chrnotropes: BB, diltiazem, verap
correct electrolyte abnormailities before starting
avoid GFJ
decrease the doses of these by 30-50% when using w/ amiodarone: warfarine, digoxin
use lower doses of simva, lova and atorvastatin

Question 6

all azoles inhibit which enzyme?

Answer 6

cyp3a4

Question 7

which of the azoles requires an acidic environment to be absorbed

Answer 7

itraconazole

ketoconazole

Question 8

name contraindicated voriconazole agents

Answer 8

barbiturates 
carbamzzepine 
rifampin
rifabutin 
ritonavir
st johns wort

Question 9

digoxin DDIs

Answer 9

BB, CCB can dec HR
cyp 3a4 and pgp substate
hypokalemia, hypercalcemia anc dec digxoicn levels

Question 10

GFJ DDIs

Answer 10

statins : lova, simva, atorva

cyp 3a4 inhibitors and inducer

Question 11

where is lithium primarily cleared?

Answer 11

renally ! just like sodium

Question 12

which agents increase lithium levels?

Answer 12

less salt intake, NSAIDS, ACEI, ARBS, dehydration

Question 13

which agents will decrease lithium levels

Answer 13

salt intake ,
cafene
theophylline

Question 14

which have additive DDI w/ lithium

Answer 14

SSRIS, 
SNRIs
Triptans,
linezolid 
RISK OF SEROTONIN SYNDROME

Question 15

what is the consequence of using non sleective MAOIs that have ddis?

Answer 15

Serotonin sydnrome
hypertensive crisis
death

Question 16

MAOI DDIS

Answer 16

SSRIS, SNRIS, TCAS
buporpion
buispirone
lithium 
linezolid
destromethorphan, triptans 
tyramine rich foods etc

Question 17

NSAIDS DDIS

Answer 17

w/ agents that cuase bleeding 
agents that raise blood pressure 
agents that causer renal toxiicty
lithium (inc lithium toxicity) 
CV toxicity

Question 18

oral contraceptives DDI

Answer 18

antibiotics: amp, smx/ doxy, rif (use backup while on antibiotic for rif for 1.5 months afterwards too.
- anticonfvulsants
- st johns wort (do not use concurrentlyO
- ATV, LPV, r, NFV, NVP
- mycophenylate reduces efficacy
- smoking

Question 19

Oxycontin and other oxycodone products

Answer 19

increased levels if cyp 3a4 inhibitors

Question 20

phosphodiesterace inhibitors DDIs

Answer 20

nitrates- severy hypotension
alpha blockers esp non selective agents
CYP3A4 substrates

Question 21

which of the FQ is mostly renally cleared

Answer 21

levofloxacin

Question 22

which of the FQ is mostly hepatically cleared?

Answer 22

moxifloxacin

Question 23

DDIs of FQ

Answer 23

Polyvalent actions, MVs, bile acids, sucralfate : chelation leading to decreased absorption
They increase Warfarin, SUs and QT prolonging drugs
-NSAIDS and probenacid increase FQ levels

Question 24

what is Rifampin a strong inducer of?

Answer 24

cyp 3A4
CYP 2C9
CYP 2c19

Question 25

which of the statins undergo extensive first pass metabolism by cyp 3a4

Answer 25

simvastatin
lovastatin
atorvastatin (but more minimal)

Question 26

max regimen of rosuvastatin on patients with ritonavir

Answer 26

10mg/day

Question 27

max rosuvastati w/ cyclosporine?

Answer 27

5mg/day

Question 28

DDI w/ tetracycliens

Answer 28

Diaveltn cations
can increase inr in warfarin
can decrease OC effectiness
avoid wi/ retinoic acid derrivatieves due to risk of pseudotumor cerebri