Antiarrhythmics Flashcards
What is a general class side effect to be aware of?
- several different effects on AP generation and propagation –> may affect autonomic NS**
Why does TdP result? When is it most commonly seen?
TdP results from QT prolongation (d/t blockade of K current)
MC with hypokalemia, hypomagnesemia, bradycardia
What is the physio behind each Vaughan-Williams class?
I: modulate or block Na+ channels
II: inhibit sympathetic activity
III: block K+ channels
IV: block Ca2+ channels
Other: digoxin
What drugs are in Class I?
Modulate or block Na+ channels
Ia: quinidine, procainamide, disopyramide
Ib: lidocaine, mexiletine
Ic: flecainide, propafenone
What drugs are in Class II?
Inhibit sympathetic activity
B-blockers
What drugs are in Class III?
Block K+ channels
- sotalol
- dofetilide
- ibutilide
- amiodarone
- dronedarone
What drugs are in Class IV?
Block Ca2+ channels
- verapamil
- diltiazem
What are “class” interactions?
- careful w/other QT prolongers
- most metabolized by 3A4 or 2D6
- drugs causing hypokalemia or hypomagnesemia (loop diuretics) INC risk
What are “class” ADRs?
Dysrhythmia
- QT prolongation / proarrhythmic potential
- careful with brady and heart blocks
What is Quinidine syncope?
Recurrent lightheadedness and fainting secondary to self-terminating TdP
[drug] usually normal or even subtherapeutic
What is cinchonism and which drug is it related to with high concentrations?
Quinidine
Dry as a bone (urinary retention) Red as a beet (vascular flushing) Blind as a bat (blurred vision) Mad as a hatter (delirium, psychosis) Hotter than hell (anhidrosis, hot skin)
What are two ADRs of procainamide?
- Reversible lupus-like syndrome**
2. potentially severe bone marrow suppression
What ADRs are related to disopyramide?
Anticholinergic, esp urinary retention
- careful w/glaucoma and BPH
What ADRs are related to Mexiletine?
CNS tox
- dizzy, lightheaded, unsteady gait
- tremor
What ADRs are related to Lidocaine?
CNS tox
- tremor MC
- seizure possible
What ADRs are related to Flecainide?
** mostly proarrhythmic –> make sure K is normal **
BBW: do not use in pt w/h/o AMI
** need echo to ensure structurally normal heart **
What ADRs are related to Propafenone?
- dysguesia (altered taste)
- lupus-like reaction
** BBW - need echo to ensure structurally normal heart **
Sotalol interactions?
Avoid concurrent B-blockers and CCBs
Has some b-blocking activity (same precautions)
What is ibutilide main ADR?
proarrhythmic activity
What is Dofetilide main ADR?
** dysrhythmia is problematic - death possible **
start med in hospital
What are two specifics related to Amiodarone chemistry?
- Iodine containing compound (like thyroxine)
- highly lipid soluble and very long half life (55 days)
What are Amio clinical indications?
FDA: life threatening recurrent VF or hemodynamically-unstable VT (ACLS)
Common unlabeled: A-fib
- AF pharm cardioversion
- AF prophylaxis following open heart surgery
- Recurrent AF
Describe the Pk Interactions of Amio?
3A4 substrate
** inhibits multiple isoenzymes moderately**
Pgp substrate & inhibitor
- may INC [digoxin] for up to 3 mo
Describe the Pd interactions of Amio?
- additive QTc drugs
- additive AV block/bradycardia
- drugs that induce INC K or Mg
** Review all interaction alerts closely for Amio **
What are the five examples given?
- DEC warfarin dose
- DEC PO digoxin
- Avoid with HCV drugs
- Avoid macrolides, FQ, fluconazole
- Careful w/statin (use rosuva)
What are the ADRs of Amio?
- Pulm
- IPF –> ARDs (interstitial infiltrates on imaging) - Thyroid (hypo)
- Ocular
- corneal microdeposits
- optic neuropathy/neuritis - Derm
- photosensitivity
- bluish skin discoloration - CNS
- gait, ataxia, dizzy, memory, peripheral neuropathy - Cardiac
- brady, AV nodal block
How does Dronedarone compare and contrast to Amiodarone?
Some MOA but
- non-iodinated analog
- shorter half life and less tissue accumulation
Clinical:
- AF, a flutter [less effective at maintaining NSR compared to amio]
Who is Dronedarone C.I. in?
- HF class IV or II-III w/recent decompensation
- Pt who cannot stay in NSR
- 2/3 deg AV block
- SSS
- Brady pt
What are 4 drug interactions to be aware of with Dronedarone?
- strong 3A4 substrate; moderate 3A4/2D6 inhibitor (remember Metoprolol, statins)
- Pgp inhibitor (remember digoxin)
- QTc prolonger
- Elevated INR with Warfarin**
What ADRs are related to Dronedarone?
Initial
- NVD
- photosensitivity (not blue though)
Emerging
- acute liver, renal failure, exacerbation of HF
Digoxin has 2 MOA depending on clinical use. What is it for HF? SV arrhythmias?
HF
- reversible inhibition of Na/K ATPase results in INC intracellular Ca
- increased contractility
SV arrhythmias
- INC vagal tone
- DEC conduction through SA, AV nodes
What are the two clinical uses of digoxin?
- Advanced systolic HF
- does not alter mortality** - 2nd line for AF in HF pts
What are three general things to monitor while on digoxin?
- ECGs (baseline, periodic)
- SCr - renal excretion (baseline, periodic)
- Cations
How can bile acid sequestrants affect digoxin?
Bile acid sequestrants may bind and impair absorption of digoxin**
How might acute dig tox manifest?
Cardiac (greatest concern)**
- PVCs**
- various degrees of AV nodal blockade**
- other electrical problems
GI: anorexia, NV, abd pain
Neuro: confusion, weakness
How might chronic dig tox manifest?
- more difficult to dx, sxs develop over days to months
** cardiac effects (rhythm disturbances) - greatest concern **
Neuro: lethargy, delirium, weak
** visual changes - color vision, development of scotomas, blindness **
How do you diagnose Dig Tox?
Clinical manifestations + ECG
Not isolated INC serum [digoxin]
How do you treat Dig Tox?
- ABCs
- Continuous tele & Pox
- Place IV
- Check BS
- Digoxin Immune Fab
- used for clinically significant arrhythmia or hypotension
