Pharm Foundations: DDI/Additive Effects Flashcards
1
Q
Amiodarone DDI
A
- Warfarin and Digoxin
- If using amiodarone first, start warfarin/digoxin at a lower dose (=<5 mg/0.125 mcg QD, respectively)
- If adding amiodarone, lower the established warfarin/digoxin dose (30-50%/50%)
- Monitor INR and HR (inform if using for rate control)
2
Q
Other HR Lowering Meds
A
- B-blockers
- Clonidine
- Verapamil
- Diltiazem
- Precedex
- Amiodarone
- Digoxin
3
Q
Digoxin + Loop Diuretics
A
- Monitor electrolyte and correct if abnormal
- Renal impairment => decrease digoxin dose or frequency, or discontinue
4
Q
Statins + Strong CYP3A4 Inhibitors
A
(Think G PACMAC)
- Increased levels of CYP3A4 substrates like lovastatin, simvastatin, and atorvastatin (increases myopathy risk)
- CI Sim/lovastatin with these agents
5
Q
Warfarin + CYP2C9 Inhibitors/Inducers
A
- Inhibitors: Azoles, SMZ/TMP, amiodarone, metronidazole
- Inducers: Rifampin, St. John’s Wort
- Decreased or increases warfarin levels respectively to increase/decrease bleeding risk
- Monitor INR
6
Q
CYP 3A4 Inhibitors + Substrates
A
- Increase drug levels and potential toxicities
- Don’t use with an opioid since with inhibitors, could increase ADRs like sedation
- Don’t take with grapefruit juice: amiodarone, sim/lovastatin, nifedipine, and tacrolimus
7
Q
Valproate + Lamotrigine
A
- Valproate decreases lamotrigine metabolism and increases risk of ADRs like skin reactions (SJS/TEN)
- Initiate lamotrigine using a starter kit and begin at lower levels
8
Q
MAOI + Catecholamine or 5HT drugs
A
- Blocking MAO with inhibitor will increase Epi/NE/DA/5HT
- High catecholamines could cause hypertensive crisis
- High 5HT could cause serotonin syndrome
- Don’t use certain antidepressants, stimulants, pain medications, and common inhibitors/inducers together for these reasons
- 2 week washout period between MAOI and serotonergic drugs (fluoxetine, 5 weeks)
- Avoid tyramine rich foods (aged cheese, air-dried meets, sauerkraut)
9
Q
CYP2D6 Inhibitors
A
- Amiodarone, fluoxetine, paroxetine, and fluvoxamine
- Don’t use together with the many CYP2D6 substrates (Decreased drug metabolism and increased ADRs)
10
Q
CYP3A4/P-gp Inhibitors/Inducers
A
- Calcineurin Inhibitors (CNIs- tacrolimus, cyclosporine) or mTOR kinase inhibitors (sirolimus, everolimus)
- Avoid using together (decreased metabolism, increased ADRs)
- With inducers increased drug metabolizing and potential risk for transplant organ rejection
11
Q
Antiepileptic CYP Inducers + Other CYP Metabolizers
A
- Phenytoin, phenobarbital, carbamazepine, oxcarbamazepine + OCDs, carbamazepine, etc.
- If substrate is lamotrigine, use starter kit/low doses
- Decrease drug levels and effects, loss of seizure control with AEDs
12
Q
Rifampin + CYP/p-gp substrates
A
- Substrate will greatly decrease
- Increase dose of substrate as necessary and monitor as needed
13
Q
CYP Inducers + Opioids
A
- Fentanyl, Hydrocodone, Oxycodone, Methadone
- Increased metabolism, decreased [opioid], pain
14
Q
CYP2D6 UM + CYP2D6 Prodrugs
A
- Codeine and tramadol
- Convert prodrug more rapidly, increase active [drug] to potential dangerous levels => toxicity
- Don’t use in children <12 years old or in a breast-feeding mother
15
Q
Smoking/Quitters
A
- Quitters - drug concentrations can increase as an CYP1A2 inducer is removed, increased toxicities
- Encourage cessation, but also monitor for toxicities/necessary monitoring parameters
- Nicotine replacement doesn’t induce
- Current smokers - decreased levels of substrate drug, may need to start at a higher initial dose (some antipsychotics, antidepressants, warfarin, anxiolytics)
